[devel] Imported from libpng-1.5.5beta06.tar

(Clifford Yap)

ANNOUNCE

@@ -1,5 +1,5 @@
 
-Libpng 1.5.4beta02 - June 14, 2011
+Libpng 1.5.5beta06 - August 25, 2011
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -9,199 +9,75 @@ Files available for download:
 Source files with LF line endings (for Unix/Linux) and with a
 "configure" script
 
-   1.5.4beta02.tar.xz (LZMA-compressed, recommended)
-   1.5.4beta02.tar.gz
-   1.5.4beta02.tar.bz2
+   1.5.5beta06.tar.xz (LZMA-compressed, recommended)
+   1.5.5beta06.tar.gz
+   1.5.5beta06.tar.bz2
 
 Source files with CRLF line endings (for Windows), without the
 "configure" script
 
-   lp154b02.7z  (LZMA-compressed, recommended)
-   lp154b02.zip
+   lp155b06.7z  (LZMA-compressed, recommended)
+   lp155b06.zip
 
 Other information:
 
-   1.5.4beta02-README.txt
-   1.5.4beta02-LICENSE.txt
+   1.5.5beta06-README.txt
+   1.5.5beta06-LICENSE.txt
 
-Changes since the last public release (1.5.2):
+Changes since the last public release (1.5.4):
 
-Version 1.5.3beta01 [April 1, 2011]
-  Re-initialize the zlib compressor before compressing non-IDAT chunks.
-  Added API functions to set parameters for zlib compression of non-IDAT
-    chunks.
+Version 1.5.5beta01 [July 13, 2011]
+  Fixed some typos and made other minor changes in the manual.
+  Updated contrib/pngminus/makefile.std (Samuli Souminen)
 
-Version 1.5.3beta02 [April 3, 2011]
-  Updated scripts/symbols.def with new API functions.
-  Only compile the new zlib re-initializing code when text or iCCP is
-    supported, using PNG_WRITE_COMPRESSED_TEXT_SUPPORTED macro.
-  Improved the optimization of the zlib CMF byte (see libpng-1.2.6beta03).
-  Optimize the zlib CMF byte in non-IDAT compressed chunks
+Version 1.5.5beta02 [July 14, 2011]
+  Revised Makefile.am and Makefile.in to look in the right directory for
+    pnglibconf.h.prebuilt
 
-Version 1.5.3beta03 [April 16, 2011]
-  Fixed gcc -ansi -pedantic compile. A strict ANSI system does not have
-    snprintf, and the "__STRICT_ANSI__" detects that condition more reliably
-    than __STDC__ (John Bowler).
-  Removed the PNG_PTR_NORETURN attribute because it too dangerous. It tells
-    the compiler that a user supplied callback (the error handler) does not
-    return, yet there is no guarantee in practice that the application code
-    will correctly implement the error handler because the compiler only
-    issues a warning if there is a mistake (John Bowler).
-  Removed the no-longer-used PNG_DEPSTRUCT macro.
-  Updated the zlib version to 1.2.5 in the VStudio project.
-  Fixed 64-bit builds where png_uint_32 is smaller than png_size_t in
-    pngwutil.c (John Bowler).
-  Fixed bug with stripping the filler or alpha channel when writing, that
-    was introduced in libpng-1.5.2beta01 (bug report by Andrew Church).
+Version 1.5.5beta03 [July 27, 2011]
+  Enabled compilation with g++ compiler.  This compiler does not recognize
+    the file extension, so it always compiles with C++ rules.  Made minor
+    changes to pngrutil.c to cast results where C++ expects it but C does not.
+  Minor editing of libpng.3 and libpng-manual.txt.
 
-Version 1.5.3beta04 [April 27, 2011]
-  Updated pngtest.png with the new zlib CMF optimization.
-  Cleaned up conditional compilation code and of background/gamma handling
-    Internal changes only except a new option to avoid compiling the
-    png_build_grayscale_palette API (which is not used at all internally.)
-    The main change is to move the transform tests (READ_TRANSFORMS,
-    WRITE_TRANSFORMS) up one level to the caller of the APIs.  This avoids
-    calls to spurious functions if all transforms are disabled and slightly
-    simplifies those functions.  Pngvalid modified to handle this.
-    A minor change is to stop the strip_16 and expand_16 interfaces from
-    disabling each other; this allows the future alpha premultiplication
-    code to use 16-bit intermediate values while still producing 8-bit output.
-    png_do_background and png_do_gamma have been simplified to take a single
-    pointer to the png_struct rather than pointers to every item required
-    from the png_struct. This makes no practical difference to the internal
-    code.
-  A serious bug in the pngvalid internal routine 'standard_display_init' has
-    been fixed - this failed to initialize the red channel and accidentally
-    initialized the alpha channel twice.
-  Changed png_struct jmp_buf member name from png_jmpbuf to tmp_jmpbuf to
-    avoid a clash with the png_jmpbuf macro on some platforms.
+Version 1.5.5beta04 [July 29, 2011]
+  Revised CMakeLists.txt (Clifford Yapp)
+  Updated commentary about the png_rgb_to_gray() default coefficients
+    in the manual and in pngrtran.c
 
-Version 1.5.3beta05 [May 6, 2011]
-  Added appropriate feature test macros to ensure libpng sees the correct API
-   _POSIX_SOURCE is defined in pngpriv.h, pngtest.c and pngvalid.c to ensure
-    that POSIX conformant systems disable non-POSIX APIs.  _ISOC99_SOURCE is
-    defined in pngpriv.h to obtain the ISO C99 snprintf definition, when
-    available.
-  Removed png_snprintf and added formatted warning messages.  This change adds
-    internal APIs to allow png_warning messages to have parameters without
-    requiring the host OS to implement snprintf.  As a side effect the
-    dependency of the tIME-supporting RFC1132 code on stdio is removed and
-    PNG_NO_WARNINGS does actually work now.
-  Added PNG_WRITE_OPTIMIZE_CMF_SUPPORTED macro to make the zlib "CMF" byte
-    optimization configureable.
-  IDAT compression failed if preceded by a compressed text chunk (bug
-    introduced in libpng-1.5.3beta01-02).  This was because the attempt to
-    reset the zlib stream in png_write_IDAT happened after the first IDAT
-    chunk had been deflated - much too late.  In this change internal
-    functions were added to claim/release the z_stream and, hopefully, make
-    the code more robust.  Also deflateEnd checking is added - previously
-    libpng would ignore an error at the end of the stream.
-
-Version 1.5.3beta06 [May 8, 2011]
-  Removed the -D_ALL_SOURCE from definitions for AIX in CMakeLists.txt
-  Implemented premultiplied alpha support: png_set_alpha_mode API
-
-Version 1.5.3beta07 [May 11, 2011]
-  Added expand_16 support to the high level interface.
-  Added named value and 'flag' gamma support to png_set_gamma.  Made a minor
-    change from the previous (unreleased) ABI/API to hide the exact value used
-    for Macs - it's not a good idea to embed this in the ABI!
-  Moved macro definitions for PNG_HAVE_IHDR, PNG_HAVE_PLTE, and PNG_AFTER_IDAT
-    from pngpriv.h to png.h because they must be visible to applications
-    that call png_set_unknown_chunks().
-  Check for up->location !PNG_AFTER_IDAT when writing unknown chunks
-    before IDAT.
-
-Version 1.5.3beta08 [May 16, 2011]
-  Improved "pngvalid --speed" to exclude more of pngvalid from the time.
-  Documented png_set_alpha_mode(), other changes in libpng.3/libpng-manual.txt
-  The cHRM chunk now sets the defaults for png_set_rgb_to_gray() (when negative
-    parameters are supplied by the caller), while in the absence of cHRM
-    sRGB/Rec 709 values are still used.
-  The bKGD chunk no longer overwrites the background value set by
-    png_set_background(), allowing the latter to be used before the file
-    header is read. It never performed any useful function to override
-    the default anyway.
-  Added memory overwrite and palette image checks to pngvalid.c
-    Previously palette image code was poorly checked. Since the transformation
-    code has a special palette path in most cases this was a severe weakness.
-  Minor cleanup and some extra checking in pngrutil.c and pngrtran.c. When
-    expanding an indexed image, always expand to RGBA if transparency is
-    present.
-
-Version 1.5.3beta09 [May 17, 2011]
- Reversed earlier 1.5.3 change of transformation order; move png_expand_16 back.
-   The change doesn't work because it requires 16-bit gamma tables when the code
-   only generates 8-bit ones.  This fails silently; the libpng code just doesn't
-   do any gamma correction.  Moving the tests back leaves the old, inaccurate,
-   8-bit gamma calculations, but these are clearly better than none!
-
-Version 1.5.3beta10 [May 20, 2011]
-  png_set_background() and png_expand_16() did not work together correctly.
-    This problem is present in 1.5.2; if png_set_background is called with
-    need_expand false and the matching 16 bit color libpng erroneously just
-    treats it as an 8-bit color because of where png_do_expand_16 is in the
-    transform list.  This simple fix reduces the supplied colour to 8-bits,
-    so it gets smashed, but this is better than the current behavior.
-  Added tests for expand16, more fixes for palette image tests to pngvalid.
-    Corrects the code for palette image tests and disables attempts to
-    validate palette colors.
-
-Version 1.5.3rc01 [June 3, 2011]
-  No changes.
-
-Version 1.5.3rc02 [June 8, 2011]
-  Fixed uninitialized memory read in png_format_buffer() (Bug report by
-    Frank Busse, related to CVE-2004-0421).
-
-Version 1.5.3beta11 [June 11, 2011]
-  Fixed png_handle_sCAL which is broken in 1.5; added sCAL to pngtest.png
-  Revised documentation about png_set_user_limits() to say that it also affects
-    png writing.
-  Revised handling of png_set_user_limits() so that it can increase the
-    limit beyond the PNG_USER_WIDTH|HEIGHT_MAX; previously it could only
-    reduce it.
-  Make the 16-to-8 scaling accurate. Dividing by 256 with no rounding is
-    wrong (high by one) 25% of the time. Dividing by 257 with rounding is
-    wrong in 128 out of 65536 cases. Getting the right answer all the time
-    without division is easy.
-  Added "_SUPPORTED" to the PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION macro.
-  Added projects/owatcom, an IDE project for OpenWatcom to replace
-    scripts/makefile.watcom.  This project works with OpenWatcom 1.9. The
-    IDE autogenerates appropriate makefiles (libpng.mk) for batch processing.
-    The project is configurable, unlike the Visual Studio project, so long
-    as the developer has an awk.
-  Changed png_set_gAMA to limit the gamma value range so that the inverse
-    of the stored value cannot overflow the fixed point representation,
-    and changed other things OpenWatcom warns about.
-  Revised pngvalid.c to test PNG_ALPHA_MODE_SUPPORTED correctly. This allows
-    pngvalid to build when ALPHA_MODE is not supported, which is required if
-    it is to build on libpng 1.4.
-  Removed string/memory macros that are no longer used and are not
-    necessarily fully supportable, particularly png_strncpy and png_snprintf.
-  Added log option to pngvalid.c and attempted to improve gamma messages.
-
-Version 1.5.3 [omitted]
-  People found the presence of a beta release following an rc release
-    to be confusing; therefore we bump the version to libpng-1.5.4beta01
-    and there will be no libpng-1.5.3 release.
-
-Version 1.5.4beta01 [June 14, 2011]
-  Made it possible to undefine PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
-    to get the same (inaccurate) output as libpng-1.5.2 and earlier.
-  Moved definitions of PNG_HAVE_IHDR, PNG_AFTER_IDAT, and PNG_HAVE_PLTE
-    outside of an unknown-chunk block in png.h because they are also
-    needed for other uses.
-
-Version 1.5.4beta02 [June 14, 2011]
-  Fixed and clarified LEGACY 16-to-8 scaling code.
-  Added png_set_chop_16() API, to match inaccurate results from previous
-    libpng versions.
-  Removed the ACCURATE and LEGACY options (they are no longer useable)
-  Use the old scaling method for background if png_set_chop_16() was
-    called.
-  Made png_set_chop_16() API removeable by disabling PNG_CHOP_16_TO_8_SUPPORTED
+Version 1.5.5beta05 [August 17, 2011]
+  Prevent unexpected API exports from non-libpng DLLs on Windows.  The "_DLL"
+    is removed from the test of whether a DLL is being built (this erroneously
+    caused the libpng APIs to be marked as DLL exports in static builds under
+    Microsoft Visual Studio).  Almost all of the libpng building configuration
+    is moved from pngconf.h to pngpriv.h, but PNG_DLL_EXPORT remains in
+    pngconf.h, though, so that it is colocated with the import definition (it
+    is no longer used anywhere in the installed headers).  The VStudio project
+    definitions have been cleaned up: "_USRDLL" has been removed from the
+    static library builds (this was incorrect), and PNG_USE_DLL has been added
+    to pngvalid to test the functionality (pngtest does not supply it,
+    deliberately).  The spurious "_EXPORTS" has been removed from the
+    libpng build (all these errors were a result of copy/paste between project
+    configurations.)
+  Added new types and internal functions for CIE RGB end point handling to
+    pngpriv.h (functions yet to be implemented).
 
+Version 1.5.5beta06 [August 25, 2011]
+  Ensure the CMAKE_LIBRARY_OUTPUT_DIRECTORY is set in CMakeLists.txt
+    (Clifford Yap)
+  Fixes to rgb_to_gray and cHRM XYZ APIs (John Bowler):
+    The rgb_to_gray code had errors when combined with gamma correction.
+    Some pixels were treated as true grey when they weren't and such pixels
+    and true grey ones were not gamma corrected (the original value of the
+    red component was used instead).  APIs to get and set cHRM using color
+    space end points have been added and the rgb_to_gray code that defaults
+    based on cHRM (introduced in 1.5.4) has been corrected.   A considerable
+    number of tests has been added to pngvalid for the rgb_to_gray transform.
+    Arithmetic errors in rgb_to_gray whereby the calculated gray value was
+    truncated to the bit depth rather than rounded have been fixed except in
+    the 8-bit non-gamma-corrected case (where consistency seems more important
+    than correctness.)  The code still has considerable inaccuracies in the
+    8-bit case because 8-bit linear arithmetic is used.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net:
 (subscription required; visit

CHANGES

@@ -180,7 +180,7 @@ Version 0.96 [May, 1997]
   Fixed serious bug with < 8bpp images introduced in 0.95
   Fixed 256-color transparency bug (Greg Roelofs)
   Fixed up documentation (Greg Roelofs, Laszlo Nyul)
-  Fixed "error" in pngconf.h for Linux setjmp() behaviour
+  Fixed "error" in pngconf.h for Linux setjmp() behavior
   Fixed DOS medium model support (Tim Wegner)
   Fixed png_check_keyword() for case with error in static string text
   Added read of CRC after IEND chunk for embedded PNGs (Laszlo Nyul)
@@ -204,8 +204,8 @@ Version 0.97 [January, 1998]
   Added more conditions for png_do_background, to avoid changing
     black pixels to background when a background is supplied and
     no pixels are transparent
-  Repaired PNG_NO_STDIO behaviour
-  Tested NODIV support and made it default behaviour (Greg Roelofs)
+  Repaired PNG_NO_STDIO behavior
+  Tested NODIV support and made it default behavior (Greg Roelofs)
   Added "-m" option and PNGTEST_DEBUG_MEMORY to pngtest (John Bowler)
   Regularized version numbering scheme and bumped shared-library major
      version number to 2 to avoid problems with libpng 0.89 apps (Greg Roelofs)
@@ -1778,7 +1778,7 @@ Version 1.2.13beta1 [October 2, 2006]
   Removed AC_FUNC_MALLOC from configure.ac
   Work around Intel-Mac compiler bug by setting PNG_NO_MMX_CODE in pngconf.h
   Change "logical" to "bitwise" throughout documentation.
-  Detect and fix attempt to write wrong iCCP profile length.
+  Detect and fix attempt to write wrong iCCP profile length (CVE-2006-7244)
 
 Version 1.0.21, 1.2.13 [November 14, 2006]
   Fix potential buffer overflow in sPLT chunk handler.
@@ -2361,7 +2361,7 @@ Version 1.4.0beta72 [August 1, 2009]
 
 Version 1.4.0beta73 [August 1, 2009]
   Reject attempt to write iCCP chunk with negative embedded profile length
-    (JD Chen)
+    (JD Chen) (CVE-2009-5063).
 
 Version 1.4.0beta74 [August 8, 2009]
   Changed png_ptr and info_ptr member "trans" to "trans_alpha".
@@ -3149,8 +3149,8 @@ version 1.5.1beta01 [January 8, 2011]
     in version 1.5.0beta36 but is not noted in the CHANGES.  Similarly,
     it was changed from png_charpp to png_const_bytepp in png_set_iCCP().
   Ensure that png_rgb_to_gray ignores palette mapped images, if libpng
-    internally happens to call it with one.
-  Fixed a failure to handle palette mapped images correctly.
+    internally happens to call it with one, and fixed a failure to handle
+    palette mapped images correctly.  This fixes CVE-2690.
 
 Version 1.5.1beta02 [January 14, 2011]
   Fixed a bug in handling of interlaced images (bero at arklinux.org).
@@ -3208,9 +3208,9 @@ Version 1.5.1beta09 [January 24, 2011]
     pngvalid contains tests of transforms, which tests are currently disabled
     because they are incompletely tested.  gray_to_rgb was failing to expand
     the bit depth for smaller bit depth images; this seems to be a long
-    standing error and resulted, apparently, in invalid output.  The
-    documentation did not accurately describe what libpng really does when
-    converting RGB to gray.
+    standing error and resulted, apparently, in invalid output
+    (CVE-2011-0408, CERT VU#643140).  The documentation did not accurately
+    describe what libpng really does when converting RGB to gray.
 
 Version 1.5.1beta10 [January 27, 2010]
   Fixed incorrect examples of callback prototypes in the manual, that were
@@ -3289,8 +3289,8 @@ Version 1.5.2 [March 31, 2011]
 
 Version 1.5.3beta01 [April 1, 2011]
   Re-initialize the zlib compressor before compressing non-IDAT chunks.
-  Added API functions to set parameters for zlib compression of non-IDAT
-    chunks.
+  Added API functions (png_set_text_compression_level() and four others) to
+    set parameters for zlib compression of non-IDAT chunks.
 
 Version 1.5.3beta02 [April 3, 2011]
   Updated scripts/symbols.def with new API functions.
@@ -3347,7 +3347,7 @@ Version 1.5.3beta05 [May 6, 2011]
     dependency of the tIME-supporting RFC1132 code on stdio is removed and
     PNG_NO_WARNINGS does actually work now.
   Pass "" instead of '\0' to png_default_error() in png_err().  This mistake
-    was introduced in libpng-1.2.20beta01.
+    was introduced in libpng-1.2.20beta01.  This fixes CVE-2011-2691.
   Added PNG_WRITE_OPTIMIZE_CMF_SUPPORTED macro to make the zlib "CMF" byte
     optimization configureable.
   IDAT compression failed if preceded by a compressed text chunk (bug
@@ -3415,10 +3415,11 @@ Version 1.5.3rc01 [June 3, 2011]
 
 Version 1.5.3rc02 [June 8, 2011]
   Fixed uninitialized memory read in png_format_buffer() (Bug report by
-    Frank Busse, related to CVE-2004-0421).
+    Frank Busse, CVE-2011-2501, related to CVE-2004-0421).
 
 Version 1.5.3beta11 [June 11, 2011]
-  Fixed png_handle_sCAL which is broken in 1.5; added sCAL to pngtest.png
+  Fixed png_handle_sCAL which is broken in 1.5. This fixes CVE 2011-2692.
+  Added sCAL to pngtest.png
   Revised documentation about png_set_user_limits() to say that it also affects
     png writing.
   Revised handling of png_set_user_limits() so that it can increase the
@@ -3465,6 +3466,103 @@ Version 1.5.4beta02 [June 14, 2011]
     called.
   Made png_set_chop_16() API removeable by disabling PNG_CHOP_16_TO_8_SUPPORTED
 
+Version 1.5.4beta03 [June 15, 2011]
+  Fixed a problem in png_do_expand_palette() exposed by optimization in
+    1.5.3beta06
+  Also removed a spurious and confusing "trans" member ("trans") from png_info.
+  The palette expand optimization prevented expansion to an intermediate RGBA
+    form if tRNS was present but alpha was marked to be stripped; this exposed
+    a check for tRNS in png_do_expand_palette() which is inconsistent with the
+    code elsewhere in libpng.
+  Correction to the expand_16 code; removed extra instance of
+    png_set_scale_16_to_8 from pngpriv.h
+
+Version 1.5.4beta04 [June 16, 2011]
+  Added a missing "#ifdef PNG_READ_BACKGROUND_SUPPORTED/#endif" in pngrtran.c
+  Added PNG_TRANSFORM_CHOP_16 to the high-level read transforms.
+  Made PNG_READ_16_TO_8_ACCURATE_SCALE configurable again.  If this is
+    not enabled, png_set_strip_16() and png_do_scale_16_to_8() aren't built.
+  Revised contrib/visupng, gregbook, and pngminim to demonstrate chop_16_to_8
+
+Version 1.5.4beta05 [June 16, 2011]
+  Renamed png_set_strip_16() to png_set_scale_16() and renamed
+    png_set_chop_16() to png_set_strip(16) in an attempt to minimize the
+    behavior changes between libpng14 and libpng15.
+
+Version 1.5.4beta06 [June 18, 2011]
+  Fixed new bug that was causing both strip_16 and scale_16 to be applied.
+
+Version 1.5.4beta07 [June 19, 2011]
+  Fixed pngvalid, simplified macros, added checking for 0 in sCAL.
+    The ACCURATE scale macro is no longer defined in 1.5 - call the
+    png_scale_16_to_8 API.  Made sure that PNG_READ_16_TO_8 is still defined
+    if the png_strip_16_to_8 API is present.  png_check_fp_number now
+    maintains some state so that positive, negative and zero values are
+    identified.  sCAL uses these to be strictly spec conformant.
+
+Version 1.5.4beta08 [June 23, 2011]
+  Fixed pngvalid if ACCURATE_SCALE is defined.
+  Updated scripts/pnglibconf.h.prebuilt.
+
+Version 1.5.4rc01 [June 30, 2011]
+  Define PNG_ALLOCATED to "restrict" only if MSC_VER >= 1400.
+
+Version 1.5.4 [July 7, 2011]
+  No changes.
+
+Version 1.5.5beta01 [July 13, 2011]
+  Fixed some typos and made other minor changes in the manual.
+  Updated contrib/pngminus/makefile.std (Samuli Souminen)
+
+Version 1.5.5beta02 [July 14, 2011]
+  Revised Makefile.am and Makefile.in to look in the right directory for
+    pnglibconf.h.prebuilt
+
+Version 1.5.5beta03 [July 27, 2011]
+  Enabled compilation with g++ compiler.  This compiler does not recognize
+    the file extension, so it always compiles with C++ rules.  Made minor
+    changes to pngrutil.c to cast results where C++ expects it but C does not.
+  Minor editing of libpng.3 and libpng-manual.txt.
+
+Version 1.5.5beta04 [July 29, 2011]
+  Revised CMakeLists.txt (Clifford Yapp)
+  Updated commentary about the png_rgb_to_gray() default coefficients
+    in the manual and in pngrtran.c
+
+Version 1.5.5beta05 [August 17, 2011]
+  Prevent unexpected API exports from non-libpng DLLs on Windows.  The "_DLL"
+    is removed from the test of whether a DLL is being built (this erroneously
+    caused the libpng APIs to be marked as DLL exports in static builds under
+    Microsoft Visual Studio).  Almost all of the libpng building configuration
+    is moved from pngconf.h to pngpriv.h, but PNG_DLL_EXPORT remains in
+    pngconf.h, though, so that it is colocated with the import definition (it
+    is no longer used anywhere in the installed headers).  The VStudio project
+    definitions have been cleaned up: "_USRDLL" has been removed from the
+    static library builds (this was incorrect), and PNG_USE_DLL has been added
+    to pngvalid to test the functionality (pngtest does not supply it,
+    deliberately).  The spurious "_EXPORTS" has been removed from the
+    libpng build (all these errors were a result of copy/paste between project
+    configurations.)
+  Added new types and internal functions for CIE RGB end point handling to
+    pngpriv.h (functions yet to be implemented).
+
+Version 1.5.5beta06 [August 25, 2011]
+  Ensure the CMAKE_LIBRARY_OUTPUT_DIRECTORY is set in CMakeLists.txt
+    (Clifford Yap)
+  Fixes to rgb_to_gray and cHRM XYZ APIs (John Bowler):
+    The rgb_to_gray code had errors when combined with gamma correction.
+    Some pixels were treated as true grey when they weren't and such pixels
+    and true grey ones were not gamma corrected (the original value of the
+    red component was used instead).  APIs to get and set cHRM using color
+    space end points have been added and the rgb_to_gray code that defaults
+    based on cHRM (introduced in 1.5.4) has been corrected.   A considerable
+    number of tests has been added to pngvalid for the rgb_to_gray transform.
+    Arithmetic errors in rgb_to_gray whereby the calculated gray value was
+    truncated to the bit depth rather than rounded have been fixed except in
+    the 8-bit non-gamma-corrected case (where consistency seems more important
+    than correctness.)  The code still has considerable inaccuracies in the
+    8-bit case because 8-bit linear arithmetic is used.
+
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
 https://lists.sourceforge.net/lists/listinfo/png-mng-implement

CMakeLists.txt

@@ -1,3 +1,11 @@
+# CMakeLists.txt
+
+# Copyright (C) 2007-2011 Glenn Randers-Pehrson
+
+# This code is released under the libpng license.
+# For conditions of distribution and use, see the disclaimer
+# and license in png.h
+
 cmake_minimum_required(VERSION 2.4.4)
 set(CMAKE_ALLOW_LOOSE_LOOP_CONSTRUCTS true)
 
@@ -25,15 +33,9 @@ endif()
 project(libpng C)
 enable_testing()
 
-# Copyright (C) 2007-2011 Glenn Randers-Pehrson
-
-# This code is released under the libpng license.
-# For conditions of distribution and use, see the disclaimer
-# and license in png.h
-
 set(PNGLIB_MAJOR 1)
 set(PNGLIB_MINOR 5)
-set(PNGLIB_RELEASE 4)
+set(PNGLIB_RELEASE 5)
 set(PNGLIB_NAME libpng${PNGLIB_MAJOR}${PNGLIB_MINOR})
 set(PNGLIB_VERSION ${PNGLIB_MAJOR}.${PNGLIB_MINOR}.${PNGLIB_RELEASE})
 
@@ -156,7 +158,6 @@ if(PNG_SHARED OR  NOT MSVC)
   add_definitions(-DZLIB_DLL)
 endif()
 
-
 if(PNG_CONSOLE_IO_SUPPORTED)
   add_definitions(-DPNG_CONSOLE_IO_SUPPORTED)
 endif()
@@ -201,7 +202,6 @@ if(PNG_STATIC)
   target_link_libraries(${PNG_LIB_NAME_STATIC} ${ZLIB_LIBRARY} ${M_LIBRARY})
 endif()
 
-
 if(PNG_SHARED AND WIN32)
   set_target_properties(${PNG_LIB_NAME} PROPERTIES DEFINE_SYMBOL PNG_BUILD_DLL)
 endif()
@@ -213,24 +213,32 @@ if(PNG_TESTS AND PNG_SHARED)
   add_test(pngtest ./pngtest ${CMAKE_CURRENT_SOURCE_DIR}/pngtest.png)
 endif()
 
-#
+# Ensure the CMAKE_LIBRARY_OUTPUT_DIRECTORY is set
+IF(NOT CMAKE_LIBRARY_OUTPUT_DIRECTORY)
+  IF(WIN32)
+    SET(CMAKE_LIBRARY_OUTPUT_DIRECTORY "bin")
+  ELSE(WIN32)
+    SET(CMAKE_LIBRARY_OUTPUT_DIRECTORY "lib")
+  ENDIF(WIN32)
+ENDIF(NOT CMAKE_LIBRARY_OUTPUT_DIRECTORY)
+
 # Set a variable with CMake code which:
 # Creates a symlink from src to dest (if possible) or alternatively
 # copies if different.
-macro(_png_generate_symlink_code CODE SRC DEST)
+macro(CREATE_SYMLINK SRC_FILE DEST_FILE)
+  FILE(REMOVE ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}/${DEST_FILE})
   if(WIN32 AND NOT CYGWIN)
-    set(_png_gsc_message "Copying ${SRC} to ${DEST} if needed")
-    set(_png_gsc_operation "copy_if_different")
-  else()
-    set(_png_gsc_message "Symlinking ${SRC} to ${DEST}")
-    set(_png_gsc_operation "create_symlink")
-  endif()
-
-  set(${CODE} "
-    message(STATUS \"${_png_gsc_message}\")
-    execute_process(COMMAND \${CMAKE_COMMAND} -E ${_png_gsc_operation}
-      \"${SRC}\" \"${DEST}\")
-    ")
+    ADD_CUSTOM_COMMAND(
+        OUTPUT ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}/${DEST_FILE}   ${CMAKE_CURRENT_BINARY_DIR}/${DEST_FILE}
+        COMMAND ${CMAKE_COMMAND} -E copy        ${CMAKE_CURRENT_BINARY_DIR}/${SRC_FILE} ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}/${DEST_FILE}
+        COMMAND ${CMAKE_COMMAND} -E copy        ${CMAKE_CURRENT_BINARY_DIR}/${SRC_FILE} ${CMAKE_CURRENT_BINARY_DIR}/${DEST_FILE}
+        DEPENDS ${PNG_LIB_NAME} ${PNG_LIB_NAME_STATIC}
+        )
+    ADD_CUSTOM_TARGET(${DEST_FILE}_COPY ALL DEPENDS ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}/${DEST_FILE})
+  else(WIN32 AND NOT CYGWIN)
+    execute_process(COMMAND ${CMAKE_COMMAND} -E create_symlink ${SRC_FILE} ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}/${DEST_FILE} WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
+    execute_process(COMMAND ${CMAKE_COMMAND} -E create_symlink ${SRC_FILE} ${DEST_FILE} WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
+  endif(WIN32 AND NOT CYGWIN)
 endmacro()
 
 # CREATE PKGCONFIG FILES
@@ -245,22 +253,16 @@ set(includedir  ${CMAKE_INSTALL_PREFIX}/include)
 set(LIBS        "-lz -lm")
 configure_file(${CMAKE_CURRENT_SOURCE_DIR}/libpng.pc.in
   ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}.pc @ONLY)
-_png_generate_symlink_code(PNG_PC_INSTALL_CODE
-  ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}.pc
-  ${CMAKE_CURRENT_BINARY_DIR}/libpng.pc)
-install(CODE ${PNG_PC_INSTALL_CODE})
+CREATE_SYMLINK(${PNGLIB_NAME}.pc libpng.pc)
 
 configure_file(${CMAKE_CURRENT_SOURCE_DIR}/libpng-config.in
   ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}-config @ONLY)
-_png_generate_symlink_code(PNG_CONFIG_INSTALL_CODE
-  ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}-config
-  ${CMAKE_CURRENT_BINARY_DIR}/libpng-config)
-install(CODE ${PNG_CONFIG_INSTALL_CODE})
+CREATE_SYMLINK(${PNGLIB_NAME}-config libpng-config)
 
 # SET UP LINKS
 if(PNG_SHARED)
   set_target_properties(${PNG_LIB_NAME} PROPERTIES
-#   VERSION 15.${PNGLIB_RELEASE}.1.5.4beta02
+#   VERSION 15.${PNGLIB_RELEASE}.1.5.5beta06
     VERSION 15.${PNGLIB_RELEASE}.0
     SOVERSION 15
     CLEAN_DIRECT_OUTPUT 1)
@@ -296,61 +298,35 @@ if(NOT SKIP_INSTALL_LIBRARIES AND NOT SKIP_INSTALL_ALL )
 
     # Create a symlink for libpng.dll.a => libpng15.dll.a on Cygwin
     if(CYGWIN)
-      _png_generate_symlink_code(PNG_SHARED_IMPLIB_INSTALL_CODE
-        ${PNGLIB_NAME}${CMAKE_IMPORT_LIBRARY_SUFFIX}
-        libpng${CMAKE_IMPORT_LIBRARY_SUFFIX})
-      install(CODE ${PNG_SHARED_IMPLIB_INSTALL_CODE})
-      install(FILES
-        ${CMAKE_CURRENT_BINARY_DIR}/libpng${CMAKE_IMPORT_LIBRARY_SUFFIX}
-        DESTINATION ${CMAKE_INSTALL_LIBDIR})
-    endif()
+       get_target_property(BUILD_TARGET_LOCATION ${PNG_LIB_NAME} LOCATION_${CMAKE_BUILD_TYPE})
+       get_filename_component(BUILD_TARGET_FILE ${BUILD_TARGET_LOCATION} NAME)
+       CREATE_SYMLINK(${BUILD_TARGET_FILE} libpng${CMAKE_IMPORT_LIBRARY_SUFFIX})
+       install(FILES ${CMAKE_CURRENT_BINARY_DIR}/libpng${CMAKE_IMPORT_LIBRARY_SUFFIX}
+         DESTINATION ${CMAKE_INSTALL_LIBDIR})
+    endif(CYGWIN)
 
     if(NOT WIN32)
-      IF(CMAKE_LIBRARY_OUTPUT_DIRECTORY)
-        _png_generate_symlink_code(PNG_SHARED_INSTALL_CODE
- ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}/${PNGLIB_NAME}${CMAKE_SHARED_LIBRARY_SUFFIX}
- ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}/libpng${CMAKE_SHARED_LIBRARY_SUFFIX})
-                install(CODE ${PNG_SHARED_INSTALL_CODE})
-                install(FILES
- ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}/libpng${CMAKE_SHARED_LIBRARY_SUFFIX}
-                DESTINATION ${CMAKE_INSTALL_LIBDIR})
-      ELSE(CMAKE_LIBRARY_OUTPUT_DIRECTORY)
-        _png_generate_symlink_code(PNG_SHARED_INSTALL_CODE
-           ${PNGLIB_NAME}${CMAKE_SHARED_LIBRARY_SUFFIX}
-           libpng${CMAKE_SHARED_LIBRARY_SUFFIX})
-        install(CODE ${PNG_SHARED_INSTALL_CODE})
-        install(FILES
-           ${CMAKE_CURRENT_BINARY_DIR}/libpng${CMAKE_SHARED_LIBRARY_SUFFIX}
-                DESTINATION ${CMAKE_INSTALL_LIBDIR})
-      ENDIF(CMAKE_LIBRARY_OUTPUT_DIRECTORY)
-    endif()
-  endif()
+      get_target_property(BUILD_TARGET_LOCATION ${PNG_LIB_NAME} LOCATION_${CMAKE_BUILD_TYPE})
+      get_filename_component(BUILD_TARGET_FILE ${BUILD_TARGET_LOCATION} NAME)
+      CREATE_SYMLINK(${BUILD_TARGET_FILE} libpng${CMAKE_SHARED_LIBRARY_SUFFIX})
+      install(FILES ${CMAKE_CURRENT_BINARY_DIR}/libpng${CMAKE_SHARED_LIBRARY_SUFFIX}
+         DESTINATION ${CMAKE_INSTALL_LIBDIR})
+    endif(NOT WIN32)
+  endif(PNG_SHARED)
 
   if(PNG_STATIC)
     install(TARGETS ${PNG_LIB_NAME_STATIC}
         ${PNG_EXPORT_RULE}
-            LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
-            ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
+        LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+        ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
     if(NOT WIN32 OR CYGWIN)
-      IF(CMAKE_ARCHIVE_OUTPUT_DIRECTORY)
-         _png_generate_symlink_code(PNG_STATIC_INSTALL_CODE
-${CMAKE_ARCHIVE_OUTPUT_DIRECTORY}/${PNGLIB_NAME}${CMAKE_STATIC_LIBRARY_SUFFIX}
-        ${CMAKE_ARCHIVE_OUTPUT_DIRECTORY}/libpng${CMAKE_STATIC_LIBRARY_SUFFIX})
-        install(CODE ${PNG_STATIC_INSTALL_CODE})
-        install(FILES
-          ${CMAKE_ARCHIVE_OUTPUT_DIRECTORY}/libpng${CMAKE_STATIC_LIBRARY_SUFFIX}
-             DESTINATION ${CMAKE_INSTALL_LIBDIR})
-      ELSE(CMAKE_ARCHIVE_OUTPUT_DIRECTORY)
-        _png_generate_symlink_code(PNG_STATIC_INSTALL_CODE
-           ${PNGLIB_NAME}${CMAKE_STATIC_LIBRARY_SUFFIX}
-           libpng${CMAKE_STATIC_LIBRARY_SUFFIX})
-        install(CODE ${PNG_STATIC_INSTALL_CODE})
-        install(FILES
-          ${CMAKE_CURRENT_BINARY_DIR}/libpng${CMAKE_STATIC_LIBRARY_SUFFIX}
-                     DESTINATION ${CMAKE_INSTALL_LIBDIR})
-      ENDIF(CMAKE_ARCHIVE_OUTPUT_DIRECTORY)
-    endif()
-  endif()
+      get_target_property(BUILD_TARGET_LOCATION ${PNG_LIB_NAME_STATIC} LOCATION_${CMAKE_BUILD_TYPE})
+      get_filename_component(BUILD_TARGET_FILE ${BUILD_TARGET_LOCATION} NAME)
+      CREATE_SYMLINK(${BUILD_TARGET_FILE} libpng${CMAKE_STATIC_LIBRARY_SUFFIX})
+      install(FILES ${CMAKE_CURRENT_BINARY_DIR}/libpng${CMAKE_STATIC_LIBRARY_SUFFIX}
+         DESTINATION ${CMAKE_INSTALL_LIBDIR})
+    endif(NOT WIN32 OR CYGWIN)
+ endif()
 endif()
 
 if(NOT SKIP_INSTALL_HEADERS AND NOT SKIP_INSTALL_ALL )
@@ -388,11 +364,9 @@ endif()
 
 # what's with libpng-$VER%.txt and all the extra files?
 
-
 # UNINSTALL
 # do we need this?
 
-
 # DIST
 # do we need this?
 

LICENSE

@@ -10,7 +10,7 @@ this sentence.
 
 This code is released under the libpng license.
 
-libpng versions 1.2.6, August 15, 2004, through 1.5.4beta02, June 14, 2011, are
+libpng versions 1.2.6, August 15, 2004, through 1.5.5beta06, August 25, 2011, are
 Copyright (c) 2004, 2006-2011 Glenn Randers-Pehrson, and are
 distributed according to the same disclaimer and license as libpng-1.2.5
 with the following individual added to the list of Contributing Authors
@@ -108,4 +108,4 @@ certification mark of the Open Source Initiative.
 
 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-June 14, 2011
+August 25, 2011

Makefile.am

@@ -97,7 +97,7 @@ $(PNGLIB_BASENAME)-config: libpng-config
 	cp libpng-config $@
 
 scripts/sym.out scripts/vers.out: png.h pngconf.h pnglibconf.h
-scripts/symbols.out: png.h pngconf.h scripts/pnglibconf.h.prebuilt
+scripts/symbols.out: png.h pngconf.h $(srcdir)/scripts/pnglibconf.h.prebuilt
 
 libpng.sym: scripts/sym.out
 	rm -f $@
@@ -108,7 +108,8 @@ libpng.vers: scripts/vers.out
 pnglibconf.h: pnglibconf.out
 	rm -f $@
 	cp $? $@
-scripts/pnglibconf.h.prebuilt:
+$(srcdir)/scripts/pnglibconf.h.prebuilt:
+	@echo "Attempting to build $@" >&2
 	@echo "This is a machine generated file, but if you want to make" >&2
 	@echo "a new one simply make 'scripts/pnglibconf.out' and copy that" >&2
 	@exit 1
@@ -162,7 +163,7 @@ scripts/pnglibconf.dfn: scripts/pnglibconf.dfa scripts/options.awk
 	test -z "$(CPPFLAGS)"
 	echo "com @PNGLIB_VERSION@ STANDARD API DEFINITION" |\
 	$(AWK) -f ${srcdir}/scripts/options.awk out=dfn1.out\
-	    logunsupported=4 - ${srcdir}/scripts/pnglibconf.dfa 1>&2
+	    logunsupported=1 - ${srcdir}/scripts/pnglibconf.dfa 1>&2
 	$(AWK) -f ${srcdir}/scripts/options.awk out=dfn2.out dfn1.out 1>&2
 	rm dfn1.out
 	mv dfn2.out $@

Makefile.in

@@ -1265,7 +1265,7 @@ $(PNGLIB_BASENAME)-config: libpng-config
 	cp libpng-config $@
 
 scripts/sym.out scripts/vers.out: png.h pngconf.h pnglibconf.h
-scripts/symbols.out: png.h pngconf.h scripts/pnglibconf.h.prebuilt
+scripts/symbols.out: png.h pngconf.h $(srcdir)/scripts/pnglibconf.h.prebuilt
 
 libpng.sym: scripts/sym.out
 	rm -f $@
@@ -1276,7 +1276,8 @@ libpng.vers: scripts/vers.out
 pnglibconf.h: pnglibconf.out
 	rm -f $@
 	cp $? $@
-scripts/pnglibconf.h.prebuilt:
+$(srcdir)/scripts/pnglibconf.h.prebuilt:
+	@echo "Attempting to build $@" >&2
 	@echo "This is a machine generated file, but if you want to make" >&2
 	@echo "a new one simply make 'scripts/pnglibconf.out' and copy that" >&2
 	@exit 1

README

@@ -1,4 +1,4 @@
-README for libpng version 1.5.4beta02 - June 14, 2011 (shared library 15.0)
+README for libpng version 1.5.5beta06 - August 25, 2011 (shared library 15.0)
 See the note about version numbers near the top of png.h
 
 See INSTALL for instructions on how to install libpng.

configure

@@ -1,6 +1,6 @@
 #! /bin/sh
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.68 for libpng 1.5.4beta02.
+# Generated by GNU Autoconf 2.68 for libpng 1.5.5beta06.
 #
 # Report bugs to <png-mng-implement@lists.sourceforge.net>.
 #
@@ -570,8 +570,8 @@ MAKEFLAGS=
 # Identity of this package.
 PACKAGE_NAME='libpng'
 PACKAGE_TARNAME='libpng'
-PACKAGE_VERSION='1.5.4beta02'
-PACKAGE_STRING='libpng 1.5.4beta02'
+PACKAGE_VERSION='1.5.5beta06'
+PACKAGE_STRING='libpng 1.5.5beta06'
 PACKAGE_BUGREPORT='png-mng-implement@lists.sourceforge.net'
 PACKAGE_URL=''
 
@@ -1307,7 +1307,7 @@ if test "$ac_init_help" = "long"; then
   # Omit some internal or obsolete options to make the list less imposing.
   # This message is too long to be a string in the A/UX 3.1 sh.
   cat <<_ACEOF
-\`configure' configures libpng 1.5.4beta02 to adapt to many kinds of systems.
+\`configure' configures libpng 1.5.5beta06 to adapt to many kinds of systems.
 
 Usage: $0 [OPTION]... [VAR=VALUE]...
 
@@ -1377,7 +1377,7 @@ fi
 
 if test -n "$ac_init_help"; then
   case $ac_init_help in
-     short | recursive ) echo "Configuration of libpng 1.5.4beta02:";;
+     short | recursive ) echo "Configuration of libpng 1.5.5beta06:";;
    esac
   cat <<\_ACEOF
 
@@ -1485,7 +1485,7 @@ fi
 test -n "$ac_init_help" && exit $ac_status
 if $ac_init_version; then
   cat <<\_ACEOF
-libpng configure 1.5.4beta02
+libpng configure 1.5.5beta06
 generated by GNU Autoconf 2.68
 
 Copyright (C) 2010 Free Software Foundation, Inc.
@@ -1908,7 +1908,7 @@ cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
 
-It was created by libpng $as_me 1.5.4beta02, which was
+It was created by libpng $as_me 1.5.5beta06, which was
 generated by GNU Autoconf 2.68.  Invocation command line was
 
   $ $0 $@
@@ -2723,7 +2723,7 @@ fi
 
 # Define the identity of the package.
  PACKAGE='libpng'
- VERSION='1.5.4beta02'
+ VERSION='1.5.5beta06'
 
 
 cat >>confdefs.h <<_ACEOF
@@ -2787,10 +2787,10 @@ fi
 
 
 
-PNGLIB_VERSION=1.5.4beta02
+PNGLIB_VERSION=1.5.5beta06
 PNGLIB_MAJOR=1
 PNGLIB_MINOR=5
-PNGLIB_RELEASE=4
+PNGLIB_RELEASE=5
 
 
 
@@ -13040,7 +13040,7 @@ cat >>$CONFIG_STATUS <<\_ACEOF || ac_write_fail=1
 # report actual input values of CONFIG_FILES etc. instead of their
 # values after options handling.
 ac_log="
-This file was extended by libpng $as_me 1.5.4beta02, which was
+This file was extended by libpng $as_me 1.5.5beta06, which was
 generated by GNU Autoconf 2.68.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
@@ -13106,7 +13106,7 @@ _ACEOF
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 ac_cs_config="`$as_echo "$ac_configure_args" | sed 's/^ //; s/[\\""\`\$]/\\\\&/g'`"
 ac_cs_version="\\
-libpng config.status 1.5.4beta02
+libpng config.status 1.5.5beta06
 configured by $0, generated by GNU Autoconf 2.68,
   with options \\"\$ac_cs_config\\"
 

configure.ac

@@ -18,15 +18,15 @@ AC_PREREQ(2.59)
 
 dnl Version number stuff here:
 
-AC_INIT([libpng], [1.5.4beta02], [png-mng-implement@lists.sourceforge.net])
+AC_INIT([libpng], [1.5.5beta06], [png-mng-implement@lists.sourceforge.net])
 AM_INIT_AUTOMAKE
 dnl stop configure from automagically running automake
 AM_MAINTAINER_MODE
 
-PNGLIB_VERSION=1.5.4beta02
+PNGLIB_VERSION=1.5.5beta06
 PNGLIB_MAJOR=1
 PNGLIB_MINOR=5
-PNGLIB_RELEASE=4
+PNGLIB_RELEASE=5
 
 dnl End of version number stuff
 

contrib/gregbook/readpng.c

@@ -229,8 +229,14 @@ uch *readpng_get_image(double display_exponent, int *pChannels, ulg *pRowbytes)
         png_set_expand(png_ptr);
     if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
         png_set_expand(png_ptr);
+#ifdef PNG_READ_16_TO_8_SUPPORTED
     if (bit_depth == 16)
+#  ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+        png_set_scale_16(png_ptr);
+#  else
         png_set_strip_16(png_ptr);
+#  endif
+#endif
     if (color_type == PNG_COLOR_TYPE_GRAY ||
         color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
         png_set_gray_to_rgb(png_ptr);

contrib/gregbook/readpng2.c

@@ -311,8 +311,14 @@ static void readpng2_info_callback(png_structp png_ptr, png_infop info_ptr)
         png_set_expand(png_ptr);
     if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
         png_set_expand(png_ptr);
+#ifdef PNG_READ_16_TO_8_SUPPORTED
     if (bit_depth == 16)
+#  ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+        png_set_scale_16(png_ptr);
+#  else
         png_set_strip_16(png_ptr);
+#  endif
+#endif
     if (color_type == PNG_COLOR_TYPE_GRAY ||
         color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
         png_set_gray_to_rgb(png_ptr);

contrib/pngminim/decoder/pngusr.dfa

@@ -36,4 +36,4 @@ option FLOATING_ARITHMETIC off
 option SETJMP on
 option STDIO on
 option READ_EXPAND on
-option READ_16_TO_8 on
+option READ_STRIP_16_TO_8 on

contrib/pngminim/preader/pngusr.dfa

@@ -36,5 +36,5 @@ option STDIO on
 option READ_bKGD on
 option READ_GAMMA on
 option READ_EXPAND on
-option READ_16_TO_8 on
+option READ_STRIP_16_TO_8 on
 option READ_GRAY_TO_RGB on

contrib/pngminus/makefile.std

@@ -8,9 +8,9 @@ LD=$(CC)
 RM=rm -f
 
 #PNGPATH = /usr/local
-#PNGINC = -I$(PNGPATH)/include/libpng12
-#PNGLIB = -L$(PNGPATH)/lib -lpng12
-#PNGLIBS = $(PNGPATH)/lib/libpng12.a
+#PNGINC = -I$(PNGPATH)/include/libpng15
+#PNGLIB = -L$(PNGPATH)/lib -lpng15
+#PNGLIBS = $(PNGPATH)/lib/libpng15.a
 PNGINC = -I../..
 PNGLIB = -L../.. -lpng
 PNGLIBS = ../../libpng.a
@@ -23,9 +23,9 @@ ZINC = -I../../../zlib
 ZLIB = -L../../../zlib -lz
 ZLIBS = ../../../zlib/libz.a
 
-CFLAGS=-O3 $(PNGINC) $(ZINC)
-LDFLAGS=$(PNGLIB) $(ZLIB)
-LDFLAGSS=$(PNGLIBS) $(ZLIBS)
+CFLAGS=$(PNGINC) $(ZINC)
+LDLIBS=$(PNGLIB) $(ZLIB)
+LDLIBSS=$(PNGLIBS) $(ZLIBS)
 C=.c
 O=.o
 L=.a
@@ -40,19 +40,19 @@ png2pnm$(O): png2pnm$(C)
 	$(CC) -c $(CFLAGS) png2pnm$(C)
 
 png2pnm$(E): png2pnm$(O)
-	$(LD) -o png2pnm$(E) png2pnm$(O) $(LDFLAGS) -lm
+	$(LD) $(LDFLAGS) -o png2pnm$(E) png2pnm$(O) $(LDLIBS) -lm
 
 png2pnm-static$(E): png2pnm$(O)
-	$(LD) -o png2pnm-static$(E) png2pnm$(O) $(LDFLAGSS) -lm
+	$(LD) $(LDFLAGS) -o png2pnm-static$(E) png2pnm$(O) $(LDLIBSS) -lm
 
 pnm2png$(O): pnm2png$(C)
 	$(CC) -c $(CFLAGS) pnm2png$(C)
 
 pnm2png$(E): pnm2png$(O)
-	$(LD) -o pnm2png$(E) pnm2png$(O) $(LDFLAGS) -lm
+	$(LD) $(LDFLAGS) -o pnm2png$(E) pnm2png$(O) $(LDLIBS) -lm
 
 pnm2png-static$(E): pnm2png$(O)
-	$(LD) -o pnm2png-static$(E) pnm2png$(O) $(LDFLAGSS) -lm
+	$(LD) $(LDFLAGS) -o pnm2png-static$(E) pnm2png$(O) $(LDLIBSS) -lm
 
 clean:
 	$(RM) png2pnm$(O)

contrib/pngminus/png2pnm.c

@@ -144,7 +144,7 @@ int main(int argc, char *argv[])
   if (png2pnm (fp_rd, fp_wr, fp_al, raw, alpha) == FALSE)
   {
     fprintf (stderr, "PNG2PNM\n");
-    fprintf (stderr, "Error:  unsuccessful convertion of PNG-image\n");
+    fprintf (stderr, "Error:  unsuccessful conversion of PNG-image\n");
     exit(1);
   }
 

contrib/visupng/PngFile.c

@@ -175,8 +175,14 @@ BOOL PngLoadImage (PTSTR pstrFileName, png_byte **ppbImageData,
         // expand images of all color-type and bit-depth to 3x8 bit RGB images
         // let the library process things like alpha, transparency, background
 
-        if (iBitDepth == 16)
-            png_set_strip_16(png_ptr);
+#ifdef PNG_READ_16_TO_8_SUPPORTED
+    if (iBitDepth == 16)
+#  ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+        png_set_scale_16(png_ptr);
+#  else
+        png_set_strip_16(png_ptr);
+#  endif
+#endif
         if (iColorType == PNG_COLOR_TYPE_PALETTE)
             png_set_expand(png_ptr);
         if (iBitDepth < 8)

example.c

@@ -2,7 +2,7 @@
 #if 0 /* in case someone actually tries to compile this */
 
 /* example.c - an example of using libpng
- * Last changed in libpng 1.5.4 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.4 [July 7, 2011]
  * This file has been placed in the public domain by the authors.
  * Maintained 1998-2011 Glenn Randers-Pehrson
  * Maintained 1996, 1997 Andreas Dilger)
@@ -187,8 +187,15 @@ void read_png(FILE *fp, unsigned int sig_read)  /* File is already open */
     * are mutually exclusive.
     */
 
-   /* Tell libpng to strip 16 bit/color files down to 8 bits/color */
+   /* Tell libpng to strip 16 bit/color files down to 8 bits/color.
+    * Use accurate scaling if it's available, otherwise just chop off the
+    * low byte.
+    */
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+    png_set_scale_16(png_ptr);
+#else
    png_set_strip_16(png_ptr);
+#endif
 
    /* Strip alpha bytes from the input data without combining with the
     * background (not recommended).

libpng-manual.txt

@@ -1,6 +1,6 @@
 libpng-manual.txt - A description on how to use and modify libpng
 
- libpng version 1.5.4beta02 - June 14, 2011
+ libpng version 1.5.5beta06 - August 25, 2011
  Updated and distributed by Glenn Randers-Pehrson
  <glennrp at users.sourceforge.net>
  Copyright (c) 1998-2011 Glenn Randers-Pehrson
@@ -11,7 +11,7 @@ libpng-manual.txt - A description on how to use and modify libpng
 
  Based on:
 
- libpng versions 0.97, January 1998, through 1.5.4beta02 - June 14, 2011
+ libpng versions 0.97, January 1998, through 1.5.5beta06 - August 25, 2011
  Updated and distributed by Glenn Randers-Pehrson
  Copyright (c) 1998-2011 Glenn Randers-Pehrson
 
@@ -107,7 +107,8 @@ PNG file.  At one time, the fields of png_info were intended to be
 directly accessible to the user.  However, this tended to cause problems
 with applications using dynamically loaded libraries, and as a result
 a set of interface functions for png_info (the png_get_*() and png_set_*()
-functions) was developed.
+functions) was developed, and direct access to the png_info fields was
+deprecated..
 
 The png_struct structure is the object used by the library to decode a
 single image.  As of 1.5.0 this structure is also not exposed.
@@ -116,14 +117,23 @@ Almost all libpng APIs require a pointer to a png_struct as the first argument.
 Many (in particular the png_set and png_get APIs) also require a pointer
 to png_info as the second argument.  Some application visible macros
 defined in png.h designed for basic data access (reading and writing
-integers in the PNG format) break this rule, but it's almost always safe
-to assume that a (png_struct*) has to be passed to call an API function.
+integers in the PNG format) don't take a png_info pointer, but it's almost
+always safe to assume that a (png_struct*) has to be passed to call an API
+function.
+
+You can have more than one png_info structure associated with an image,
+as illustrated in pngtest.c, one for information valid prior to the
+IDAT chunks and another (called "end_info" below) for things after them.
 
 The png.h header file is an invaluable reference for programming with libpng.
 And while I'm on the topic, make sure you include the libpng header file:
 
 #include <png.h>
 
+and also (as of libpng-1.5.0) the zlib header file, if you need it:
+
+#include <zlib.h>
+
 Types
 
 The png.h header file defines a number of integral types used by the
@@ -137,9 +147,9 @@ the value by multiplying by 100,000.  As of libpng 1.5.0 a convenience
 macro PNG_FP_1 is defined in png.h along with a type (png_fixed_point)
 which is simply (png_int_32).
 
-All APIs that take (double) arguments also have an matching API that
+All APIs that take (double) arguments also have a matching API that
 takes the corresponding fixed point integer arguments.  The fixed point
-API has the same name as the floating point one with _fixed appended.
+API has the same name as the floating point one with "_fixed" appended.
 The actual range of values permitted in the APIs is frequently less than
 the full range of (png_fixed_point) (-21474 to +21474).  When APIs require
 a non-negative argument the type is recorded as png_uint_32 above.  Consult
@@ -157,6 +167,10 @@ preprocessing directives of the form:
     #ifdef PNG_feature_SUPPORTED
     declare-function
     #endif
+    ...
+    #ifdef PNG_feature_SUPPORTED
+    use-function
+    #endif
 
 The library can be built without support for these APIs, although a
 standard build will have all implemented APIs.  Application programs
@@ -165,7 +179,7 @@ portability.  From libpng 1.5.0 the feature macros set during the build
 of libpng are recorded in the header file "pnglibconf.h" and this file
 is always included by png.h.
 
-If you don't need to change the library configuration from the default skip to
+If you don't need to change the library configuration from the default, skip to
 the next section ("Reading").
 
 Notice that some of the makefiles in the 'scripts' directory and (in 1.5.0) all
@@ -197,24 +211,25 @@ A variety of methods exist to build libpng.  Not all of these support
 reconfiguration of pnglibconf.h.  To reconfigure pnglibconf.h it must either be
 rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand.
 
-Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt and changing
-the lines defining the supported features, paying very close attention to the
-'option' information in scripts/pnglibconf.dfa that describes those features and
-their requirements.  This is easy to get wrong.
+Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt to
+pnglibconf.h and changing the lines defining the supported features, paying
+very close attention to the 'option' information in scripts/pnglibconf.dfa
+that describes those features and their requirements.  This is easy to get
+wrong.
 
 B. Configuration using DFA_XTRA
 
 Rebuilding from pnglibconf.dfa is easy if a functioning 'awk', or a later
 variant such as 'nawk' or 'gawk', is available.  The configure build will
 automatically find an appropriate awk and build pnglibconf.h.
-scripts/pnglibconf.mak contains a set of make rules for doing the same thing if
-configure is not used, and many of the makefiles in the scripts directory use
-this approach.
+The scripts/pnglibconf.mak file contains a set of make rules for doing the
+same thing if configure is not used, and many of the makefiles in the scripts
+directory use this approach.
 
-When rebuilding simply write new file containing changed options and set
+When rebuilding simply write a new file containing changed options and set
 DFA_XTRA to the name of this file.  This causes the build to append the new file
-to the end of scripts/pnglibconf.dfa.  pngusr.dfa should contain lines of the
-following forms:
+to the end of scripts/pnglibconf.dfa.  The pngusr.dfa file should contain lines
+of the following forms:
 
 everything = off
 
@@ -238,12 +253,16 @@ source code.  Most of these values have performance implications for the library
 but most of them have no visible effect on the API.  Some can also be overridden
 from the API.
 
+This method of building a customized pnglibconf.h is illustrated in
+contrib/pngminim/*.  See the "$(PNGCONF):" target in the makefile and
+pngusr.dfa in these directories.
+
 C. Configuration using PNG_USR_CONFIG
 
 If -DPNG_USR_CONFIG is added to the CFLAGS when pnglibconf.h is built the file
 pngusr.h will automatically be included before the options in
-scripts/pnglibconf.dfa are processed.  pngusr.h should contain only macro
-definitions turning features on or off or setting settings.
+scripts/pnglibconf.dfa are processed.  Your pngusr.h file should contain only
+macro definitions turning features on or off or setting settings.
 
 Apart from the global setting "everything = off" all the options listed above
 can be set using macros in pngusr.h:
@@ -274,6 +293,9 @@ examine the intermediate file pnglibconf.dfn to find the full set of
 dependency information for each setting and option.  Simply locate the
 feature in the file and read the C comments that precede it.
 
+This method is also illustrated in the contrib/pngminim/* makefiles and
+pngusr.h.
+
 III. Reading
 
 We'll now walk you through the possible functions to call when reading
@@ -557,6 +579,8 @@ according to the "keep" directive.  If a chunk is named in successive
 instances of png_set_keep_unknown_chunks(), the final instance will
 take precedence.  The IHDR and IEND chunks should not be named in
 chunk_list; if they are, libpng will process them normally anyway.
+If you know that your application will never make use of some particular
+chunks, use PNG_HANDLE_CHUNK_NEVER (or 1) as demonstrated below.
 
 Here is an example of the usage of png_set_keep_unknown_chunks(),
 where the private "vpAg" chunk will later be processed by a user chunk
@@ -647,13 +671,14 @@ If you intend to display the PNG or to incorporate it in other image data you
 need to tell libpng information about your display or drawing surface so that
 libpng can convert the values in the image to match the display.
 
-From libpng-1.5.3 this information can be set before reading the PNG file
+From libpng-1.5.4 this information can be set before reading the PNG file
 header.  In earlier versions png_set_gamma() existed but behaved incorrectly if
 called before the PNG file header had been read and png_set_alpha_mode() did not
 exist.
 
-If you need to support versions prior to libpng-1.5.3 test the version number
-and follow the procedures described in the appropriate manual page.
+If you need to support versions prior to libpng-1.5.4 test the version number
+as illustrated below using "PNG_LIBPNG_VER >= 10504" and follow the procedures
+described in the appropriate manual page.
 
 You give libpng the encoding expected by your system expressed as a 'gamma'
 value.  You can also specify a default encoding for the PNG file in
@@ -673,7 +698,7 @@ documentation!
 
 Many systems permit the system gamma to be changed via a lookup table in the
 display driver, a few systems, including older Macs, change the response by
-default.  As of 1.5.3 three special values are available to handle common
+default.  As of 1.5.4 three special values are available to handle common
 situations:
 
    PNG_DEFAULT_sRGB: Indicates that the system conforms to the IEC 61966-2-1
@@ -698,7 +723,9 @@ Libpng only supports composing onto a single color (using png_set_background;
 see below.)  Otherwise you must do the composition yourself and, in this case,
 you may need to call png_set_alpha_mode:
 
+#if PNG_LIBPNG_VER >= 10504
    png_set_alpha_mode(png_ptr, mode, screen_gamma);
+#endif
 
 The screen_gamma value is the same as the argument to png_set_gamma, however how
 it affects the output depends on the mode.  png_set_alpha_mode() sets the file
@@ -838,17 +865,22 @@ format produced by libpng to always have 8-bit or 16-bit components and then
 store the color as an 8-bit or 16-bit color as appropriate.  The color contains
 separate gray and RGB component values, so you can let libpng produce gray or
 RGB output according to the input format, but low bit depth grayscale images
-must always be converted to at least 8-bit format.  (Even low low bit depth
+must always be converted to at least 8-bit format.  (Even though low bit depth
 grayscale images can't have an alpha channel they can have a transparent
 color!)
 
 You set the transforms you need later, either as flags to the high level
 interface or libpng API calls for the low level interface.  For reference the
-settings required are:
+settings and API calls required are:
 
 8-bit values:
-   PNG_TRANSFORM_STRIP_16 | PNG_EXPAND
-   png_set_expand(png_ptr); png_set_strip_16(png_ptr);
+   PNG_TRANSFORM_SCALE_16 | PNG_EXPAND
+   png_set_expand(png_ptr); png_set_scale_16(png_ptr);
+
+   If you must get exactly the same inaccurate results
+   produced by default in versions prior to libpng-1.5.4,
+   use PNG_TRANSFORM_STRIP_16 and png_set_strip_16(png_ptr)
+   instead.
 
 16-bit values:
    PNG_TRANSFORM_EXPAND_16
@@ -859,9 +891,9 @@ color data you can add PNG_TRANSFORM_GRAY_TO_RGB or png_set_gray_to_rgb(png_ptr)
 to the list.
 
 Calling png_set_background before the PNG file header is read will not work
-prior to libpng-1.5.3.  Because the failure may result in unexpected warnings or
+prior to libpng-1.5.4.  Because the failure may result in unexpected warnings or
 errors it is therefore much safer to call png_set_background after the head has
-been read.  Unfortunately this means that prior to libpng-1.5.3 it cannot be
+been read.  Unfortunately this means that prior to libpng-1.5.4 it cannot be
 used with the high level interface.
 
 The high-level read interface
@@ -873,8 +905,10 @@ the entire image into memory, and (b) the input transformations
 you want to do are limited to the following set:
 
     PNG_TRANSFORM_IDENTITY      No transformation
-    PNG_TRANSFORM_STRIP_16      Strip 16-bit samples to
-                                8-bit
+    PNG_TRANSFORM_SCALE_16      Strip 16-bit samples to
+                                8-bit accurately
+    PNG_TRANSFORM_STRIP_16      Chop 16-bit samples to
+                                8-bit less accurately
     PNG_TRANSFORM_STRIP_ALPHA   Discard the alpha channel
     PNG_TRANSFORM_PACKING       Expand 1, 2 and 4-bit
                                 samples to bytes
@@ -968,9 +1002,9 @@ for use in later transformations.  Important information copied in is:
 1) The PNG file gamma from the gAMA chunk.  This overwrites the default value
 provided by an earlier call to png_set_gamma or png_set_alpha_mode.
 
-2) Prior to libpng-1.5.3 the background color from a bKGd chunk.  This
+2) Prior to libpng-1.5.4 the background color from a bKGd chunk.  This
 damages the information provided by an earlier call to png_set_background
-resulting in expected behavior.  Libpng-1.5.3 no longer does this.
+resulting in unexpected behavior.  Libpng-1.5.4 no longer does this.
 
 3) The number of significant bits in each component value.  Libpng uses this to
 optimize gamma handling by reducing the internal lookup table sizes.
@@ -1108,6 +1142,28 @@ pointer into the info_ptr is returned for any complex types.
     int_file_gamma - 100,000 times the gamma at which the
                      file is written
 
+    png_get_cHRM(png_ptr, info_ptr,  &white_x, &white_y, &red_x, &red_y,
+                     &green_x, &green_y, &blue_x, &blue_y)
+    png_get_cHRM_XYZ(png_ptr, info_ptr, &red_X, &red_Y, &red_Z, &green_X,
+                     &green_Y, &green_Z, &blue_X, &blue_Y, &blue_Z)
+    png_get_cHRM_fixed(png_ptr, info_ptr, &int_white_x, &int_white_y,
+                     &int_red_x, &int_red_y, &int_green_x, &int_green_y,
+                     &int_blue_x, &int_blue_y)
+    png_get_cHRM_XYZ_fixed(png_ptr, info_ptr, &int_red_X, &int_red_Y,
+                     &int_red_Z, &int_green_X, &int_green_Y, &int_green_Z,
+                     &int_blue_X, &int_blue_Y, &int_blue_Z)
+
+    {white,red,green,blue}_{x,y}
+                     A color space encoding specified using the chromaticities
+                     of the end points and the white point. (PNG_INFO_cHRM)
+
+    {red,green,blue}_{X,Y,Z}
+                     A color space encoding specified using the encoding end
+                     points - the CIE tristimulus specification of the intended
+                     color of the red, green and blue channels in the PNG RGB
+                     data.  The white point is simply the sum of the three end
+                     points. (PNG_INFO_cHRM)
+
     png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
 
     file_srgb_intent - the rendering intent (PNG_INFO_sRGB)
@@ -1166,7 +1222,8 @@ pointer into the info_ptr is returned for any complex types.
 
     png_get_bKGD(png_ptr, info_ptr, &background);
 
-    background     - background color (PNG_VALID_bKGD)
+    background     - background color (of type
+                     png_color_16p) (PNG_VALID_bKGD)
                      valid 16-bit red, green and blue
                      values, regardless of color_type
 
@@ -1205,6 +1262,8 @@ pointer into the info_ptr is returned for any complex types.
     Note that the itxt_length, lang, and lang_key
     members of the text_ptr structure only exist
     when the library is built with iTXt chunk support.
+    Prior to libpng-1.4.0, the default build was
+    without iTXt chunk support.
 
     num_text       - number of comments (same as
                      num_comments; you can put NULL here
@@ -1229,10 +1288,10 @@ pointer into the info_ptr is returned for any complex types.
        &unit_type);
 
     offset_x       - positive offset from the left edge
-                     of the screen
+                     of the screen (can be negative)
 
     offset_y       - positive offset from the top edge
-                     of the screen
+                     of the screen (can be negative)
 
     unit_type      - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
 
@@ -1264,6 +1323,7 @@ pointer into the info_ptr is returned for any complex types.
     unit        - physical scale units (an integer)
 
     width       - width of a pixel in physical scale units
+                  (expressed as a string)
 
     height      - height of a pixel in physical scale units
                  (width and height are strings like "2.54")
@@ -1286,6 +1346,12 @@ pointer into the info_ptr is returned for any complex types.
     chunks were read from the PNG file or inserted with the
     png_set_unknown_chunks() function.
 
+    The value of "location" is a bitwise "or" of
+
+         PNG_HAVE_IHDR  (0x01)
+         PNG_HAVE_PLTE  (0x02)
+         PNG_AFTER_IDAT (0x08)
+
 The data from the pHYs chunk can be retrieved in several convenient
 forms:
 
@@ -1399,12 +1465,12 @@ byte, unless png_set_packing() is called.  8-bit RGB data will be stored
 in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha()
 is called to insert filler bytes, either before or after each RGB triplet.
 16-bit RGB data will be returned RRGGBB RRGGBB, with the most significant
-byte of the color value first, unless png_set_strip_16() is called to
+byte of the color value first, unless png_set_scale_16() is called to
 transform it to regular RGB RGB triplets, or png_set_filler() or
 png_set_add alpha() is called to insert filler bytes, either before or
 after each RRGGBB triplet.  Similarly, 8-bit or 16-bit grayscale data can
-be modified with
-png_set_filler(), png_set_add_alpha(), or png_set_strip_16().
+be modified with png_set_filler(), png_set_add_alpha(), png_set_strip_16(),
+or png_set_scale_16().
 
 The following code transforms grayscale images of less than 8 to 8 bits,
 changes paletted images to RGB, and adds a full alpha channel if there is
@@ -1430,7 +1496,7 @@ As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was
 added.  It expands the sample depth without changing tRNS to alpha.
 
 As of libpng version 1.5.2, png_set_expand_16() was added.  It behaves as
-png_set_expand(), however, the resultant channels have 16 bits rather than 8.
+png_set_expand(); however, the resultant channels have 16 bits rather than 8.
 Use this when the output color or gray channels are made linear to avoid fairly
 severe accuracy loss.
 
@@ -1441,7 +1507,14 @@ PNG can have files with 16 bits per channel.  If you only can handle
 8 bits per channel, this will strip the pixels down to 8-bit.
 
     if (bit_depth == 16)
+#if PNG_LIBPNG_VER >= 10504
+       png_set_scale_16(png_ptr);
+#else
        png_set_strip_16(png_ptr);
+#endif
+
+(The more accurate "png_set_scale_16()" API became available in libpng version
+1.5.4).
 
 If you need to process the alpha channel on the image separately from the image
 data (for example if you convert it to a bitmap mask) it is possible to have
@@ -1619,31 +1692,41 @@ It will return a png_byte that is zero if the image was gray or
 will be silently converted to grayscale, using the green channel
 data for sBIT, regardless of the error_action setting.
 
-The default values come from the PNG file cHRM chunk if present, otherwise the
+The default values come from the PNG file cHRM chunk if present; otherwise, the
 defaults correspond to the ITU-R recommendation 709, and also the sRGB color
 space, as recommended in the Charles Poynton's Colour FAQ,
 <http://www.poynton.com/>, in section 9:
 
    <http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9>
 
+    Y = 0.2126 * R + 0.7152 * G + 0.0722 * B
+
+Previous versions of this document, 1998 through 2002, recommended a slightly
+different formula:
+
     Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
 
+Libpng uses an integer approximation:
+
+    Y = (6968 * R + 23434 * G + 2366 * B)/32768
+
 The calculation is done in a linear colorspace, if the image gamma
 can be determined.
 
-The png_set_background() function has been described already, it tells libpng to
+The png_set_background() function has been described already; it tells libpng to
 composite images with alpha or simple transparency against the supplied
 background color.  For compatibility with versions of libpng earlier than
-libpng-1.5.3 it is recommended that you call the function after reading the file
+libpng-1.5.4 it is recommended that you call the function after reading the file
 header, even if you don't want to use the color in a bKGD chunk, if one exists.
 
 If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid),
 you may use this color, or supply another color more suitable for
 the current display (e.g., the background color from a web page).  You
 need to tell libpng how the color is represented, both the format of the
-component values in the color (the number of bits) and the gamme encoding of the
+component values in the color (the number of bits) and the gamma encoding of the
 color.  The function takes two arguments, background_gamma_mode and need_expand
-to convey this information, however only two combinations are like to be useful:
+to convey this information, however only two combinations are likely to be
+useful:
 
     png_color_16 my_background;
     png_color_16p image_background;
@@ -1655,7 +1738,6 @@ to convey this information, however only two combinations are like to be useful:
        png_set_background(png_ptr, &my_background,
            PNG_BACKGROUND_GAMMA_SCREEN, 0/*do not expand*/, 1);
 
-
 The second call was described above - my_background is in the format of the
 final, display, output produced by libpng.  Because you now know the format of
 the PNG it is possible to avoid the need to choose either 8-bit or 16-bit
@@ -1671,7 +1753,7 @@ image_background->gray.
 
 If you didn't call png_set_gamma() before reading the file header, for example
 if you need your code to remain compatible with older versions of libpng prior
-to libpng-1.5.3, this is the place to call it.
+to libpng-1.5.4, this is the place to call it.
 
 Do not call it if you called png_set_alpha_mode(); doing so will damage the
 settings put in place by png_set_alpha_mode().  (If png_set_alpha_mode() is
@@ -1694,9 +1776,9 @@ file has more entries then will fit on your screen, png_set_quantize()
 will do that.  Note that this is a simple match quantization that merely
 finds the closest color available.  This should work fairly well with
 optimized palettes, but fairly badly with linear color cubes.  If you
-pass a palette that is larger then maximum_colors, the file will
+pass a palette that is larger than maximum_colors, the file will
 reduce the number of colors in the palette so it will fit into
-maximum_colors.  If there is a histogram, it will use it to make
+maximum_colors.  If there is a histogram, libpng will use it to make
 more intelligent choices when reducing the palette.  If there is no
 histogram, it may not do as good a job.
 
@@ -1768,7 +1850,7 @@ after all of the other transformations have been processed.  Take care with
 interlaced images if you do the interlace yourself - the width of the row is the
 width in 'row_info', not the overall image width.
 
-If supported libpng provides two information routines that you can use to find
+If supported, libpng provides two information routines that you can use to find
 where you are in processing the image:
 
    png_get_current_pass_number(png_structp png_ptr);
@@ -2632,6 +2714,28 @@ width, height, bit_depth, and color_type must be the same in each call.
     int_file_gamma - 100,000 times the gamma at which
                      the image was created
 
+    png_set_cHRM(png_ptr, info_ptr,  white_x, white_y, red_x, red_y,
+                     green_x, green_y, blue_x, blue_y)
+    png_set_cHRM_XYZ(png_ptr, info_ptr, red_X, red_Y, red_Z, green_X,
+                     green_Y, green_Z, blue_X, blue_Y, blue_Z)
+    png_set_cHRM_fixed(png_ptr, info_ptr, int_white_x, int_white_y,
+                     int_red_x, int_red_y, int_green_x, int_green_y,
+                     int_blue_x, int_blue_y)
+    png_set_cHRM_XYZ_fixed(png_ptr, info_ptr, int_red_X, int_red_Y,
+                     int_red_Z, int_green_X, int_green_Y, int_green_Z,
+                     int_blue_X, int_blue_Y, int_blue_Z)
+
+    {white,red,green,blue}_{x,y}
+                     A color space encoding specified using the chromaticities
+                     of the end points and the white point.
+
+    {red,green,blue}_{X,Y,Z}
+                     A color space encoding specified using the encoding end
+                     points - the CIE tristimulus specification of the intended
+                     color of the red, green and blue channels in the PNG RGB
+                     data.  The white point is simply the sum of the three end
+                     points.
+
     png_set_sRGB(png_ptr, info_ptr, srgb_intent);
 
     srgb_intent    - the rendering intent
@@ -2692,14 +2796,14 @@ width, height, bit_depth, and color_type must be the same in each call.
     trans_alpha    - array of alpha (transparency)
                      entries for palette (PNG_INFO_tRNS)
 
+    num_trans      - number of transparent entries
+                     (PNG_INFO_tRNS)
+
     trans_color    - graylevel or color sample values
                      (in order red, green, blue) of the
                      single transparent color for
                      non-paletted images (PNG_INFO_tRNS)
 
-    num_trans      - number of transparent entries
-                     (PNG_INFO_tRNS)
-
     png_set_hIST(png_ptr, info_ptr, hist);
 
     hist           - histogram of palette (array of
@@ -2712,7 +2816,8 @@ width, height, bit_depth, and color_type must be the same in each call.
 
     png_set_bKGD(png_ptr, info_ptr, background);
 
-    background     - background color (PNG_VALID_bKGD)
+    background     - background color (of type
+                     png_color_16p) (PNG_VALID_bKGD)
 
     png_set_text(png_ptr, info_ptr, text_ptr, num_text);
 
@@ -2739,6 +2844,8 @@ width, height, bit_depth, and color_type must be the same in each call.
     Note that the itxt_length, lang, and lang_key
     members of the text_ptr structure only exist
     when the library is built with iTXt chunk support.
+    Prior to libpng-1.4.0 the library was built by default
+    without iTXt support.
 
     num_text       - number of comments
 
@@ -2788,6 +2895,7 @@ width, height, bit_depth, and color_type must be the same in each call.
     unit        - physical scale units (an integer)
 
     width       - width of a pixel in physical scale units
+                  expressed as a string
 
     height      - height of a pixel in physical scale units
                  (width and height are strings like "2.54")
@@ -2829,7 +2937,7 @@ Because tEXt and zTXt chunks don't have a language field, if you
 specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt
 any language code or translated keyword will not be written out.
 
-Until text gets around 1000 bytes, it is not worth compressing it.
+Until text gets around a few hundred bytes, it is not worth compressing it.
 After the text has been written out to the file, the compression type
 is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR,
 so that it isn't written out again at the end (in case you are calling
@@ -3439,7 +3547,8 @@ However, there are some uncertainties about the status of local variables
 after a longjmp, so the user may want to be careful about doing anything
 after setjmp returns non-zero besides returning itself.  Consult your
 compiler documentation for more details.  For an alternative approach, you
-may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net).
+may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net),
+which is illustrated in pngvalid.c and in contrib/visupng.
 
 Custom chunks
 
@@ -3457,8 +3566,11 @@ and look at how other chunks were designed, so you can do things
 similarly.  Second, check out the sections of libpng that read and
 write chunks.  Try to find a chunk that is similar to yours and use
 it as a template.  More details can be found in the comments inside
-the code.  It is best to handle unknown chunks in a generic method,
-via callback functions, instead of by modifying libpng functions.
+the code.  It is best to handle private or unknown chunks in a generic method,
+via callback functions, instead of by modifying libpng functions. This
+is illustrated in pngtest.c, which uses a callback function to handle a
+private "vpAg" chunk and the new "sTER" chunk, which are both unknown to
+libpng.
 
 If you wish to write your own transformation for the data, look through
 the part of the code that does the transformations, and check out some of
@@ -3486,8 +3598,8 @@ defined, and FAR gets defined to far in pngconf.h, and you should be
 all set.  Everything in the library (except for zlib's structure) is
 expecting far data.  You must use the typedefs with the p or pp on
 the end for pointers (or at least look at them and be careful).  Make
-note that the rows of data are defined as png_bytepp, which is an
-unsigned char far * far *.
+note that the rows of data are defined as png_bytepp, which is
+an "unsigned char far * far *".
 
 Configuring for gui/windowing platforms:
 
@@ -3505,7 +3617,10 @@ or delete an include, this is the place to do it.
 The includes that are not needed outside libpng are placed in pngpriv.h,
 which is only used by the routines inside libpng itself.
 The files in libpng proper only include pngpriv.h and png.h, which
-in turn includes pngconf.h.
+in turn includes pngconf.h and, as of libpng-1.5.0, pnglibconf.h.
+As of libpng-1.5.0, pngpriv.h also includes three other private header
+files, pngstruct.h, pnginfo.h, and pngdebug.h, which contain material
+that previously appeared in the public headers.
 
 Configuring zlib:
 
@@ -3547,8 +3662,28 @@ zlib.h for more information on what these mean.
         window_bits);
 
     png_set_compression_method(png_ptr, method);
+
     png_set_compression_buffer_size(png_ptr, size);
 
+As of libpng version 1.5.4, additional APIs became
+available to set these separately for non-IDAT
+compressed chunks such as zTXt, iTXt, and iCCP:
+
+    #include zlib.h
+    #if PNG_LIBPNG_VER <= 10504
+    png_set_text_compression_level(png_ptr, level);
+
+    png_set_text_compression_mem_level(png_ptr, level);
+
+    png_set_text_compression_strategy(png_ptr,
+        strategy);
+
+    png_set_text_compression_window_bits(png_ptr,
+        window_bits);
+
+    png_set_text_compression_method(png_ptr, method);
+    #endif
+
 Controlling row filtering
 
 If you want to control whether libpng uses filtering or not, which
@@ -3654,8 +3789,8 @@ capability, which you'll still have).
 All the reading and writing specific code are in separate files, so the
 linker should only grab the files it needs.  However, if you want to
 make sure, or if you are building a stand alone library, all the
-reading files start with pngr and all the writing files start with
-pngw.  The files that don't match either (like png.c, pngtrans.c, etc.)
+reading files start with "pngr" and all the writing files start with "pngw".
+The files that don't match either (like png.c, pngtrans.c, etc.)
 are used for both reading and writing, and always need to be included.
 The progressive reader is in pngpread.c
 
@@ -4033,7 +4168,6 @@ absolutely necessary) interlace an image.
 
 libpng 1.5.0 adds an API png_longjmp(png_ptr, value).  This API calls
 the application-provided png_longjmp_ptr on the internal, but application
-initialized, jmpbuf.  It is provided as a convenience to avoid the need
 initialized, longjmp buffer.  It is provided as a convenience to avoid
 the need to use the png_jmpbuf macro, which had the unnecessary side
 effect of resetting the internal png_longjmp_ptr value.
@@ -4090,20 +4224,20 @@ PNG_NO_USE_READ_MACROS before including png.h.  Notice that this is
 only supported from 1.5.0 -defining PNG_NO_USE_READ_MACROS prior to 1.5.0
  will lead to a link failure.
 
-Prior to libpng-1.5.3, the zlib compressor used the same set of parameters
+Prior to libpng-1.5.4, the zlib compressor used the same set of parameters
 when compressing the IDAT data and textual data such as zTXt and iCCP.
-In libpng-1.5.3 we reinitialized the zlib stream for each type of data.
+In libpng-1.5.4 we reinitialized the zlib stream for each type of data.
 We added five png_set_text_*() functions for setting the parameters to
 use with textual data.
 
-Prior to libpng-1.5.3, the PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
+Prior to libpng-1.5.4, the PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
 option was off by default, and slightly inaccurate scaling occurred.
-This option can no longer be turned off, and 16-to-8 scaling is always
-accurate.  This change will result in some different results while
-reading 16-bit images, with none of the pixels being off-by-one any
-longer (see Clause 13.12 of the PNG specification).
+This option can no longer be turned off, and the choice of accurate
+or inaccurate 16-to-8 scaling is by using the new png_set_scale_16_to_8()
+API for accurate scaling or the old png_set_strip_16_to_8() API for simple
+chopping.
 
-Prior to libpng-1.5.3, the png_set_user_limits() function could only be
+Prior to libpng-1.5.4, the png_set_user_limits() function could only be
 used to reduce the width and height limits from the value of
 PNG_USER_WIDTH_MAX and PNG_USER_HEIGHT_MAX, although this document said
 that it could be used to override them.  Now this function will reduce or
@@ -4112,9 +4246,9 @@ increase the limits.
 B. Changes to the build and configuration of libpng
 
 Details of internal changes to the library code can be found in the CHANGES
-file.  These will be of no concern to the vast majority of library users or
-builders, however the few who configure libpng to a non-default feature
-set may need to change how this is done.
+file and in the GIT repository logs.  These will be of no concern to the vast
+majority of library users or builders, however the few who configure libpng
+to a non-default feature set may need to change how this is done.
 
 There should be no need for library builders to alter build scripts if
 these use the distributed build support - configure or the makefiles -
@@ -4123,14 +4257,14 @@ to build pnglibconf.h where the corresponding makefile does not do so.
 
 Building libpng with a non-default configuration has changed completely.
 The old method using pngusr.h should still work correctly even though the
-way pngusr.h is used in the build has been changed, however library
+way pngusr.h is used in the build has been changed; however, library
 builders will probably want to examine the changes to take advantage of
 new capabilities and to simplify their build system.
 
 B.1 Specific changes to library configuration capabilities
 
 The library now supports a complete fixed point implementation and can
-thus be used on systems which have no floating point support or very
+thus be used on systems that have no floating point support or very
 limited or slow support.  Previously gamma correction, an essential part
 of complete PNG support, required reasonably fast floating point.
 
@@ -4146,14 +4280,14 @@ pnglibconf.h
 As part of this the mechanism used to choose procedure call standards on
 those systems that allow a choice has been changed.  At present this only
 affects certain Microsoft (DOS, Windows) and IBM (OS/2) operating systems
-running on Intel processors.  As before PNGAPI is defined where required
+running on Intel processors.  As before, PNGAPI is defined where required
 to control the exported API functions; however, two new macros, PNGCBAPI
 and PNGCAPI, are used instead for callback functions (PNGCBAPI) and
 (PNGCAPI) for functions that must match a C library prototype (currently
 only png_longjmp_ptr, which must match the C longjmp function.)  The new
 approach is documented in pngconf.h
 
-Despite these changes libpng 1.5.0 only supports the native C function
+Despite these changes, libpng 1.5.0 only supports the native C function
 calling standard on those platforms tested so far (__cdecl on Microsoft
 Windows).  This is because the support requirements for alternative
 calling conventions seem to no longer exist.  Developers who find it
@@ -4186,8 +4320,10 @@ if the feature is supported or:
 /*#undef PNG_feature_SUPPORTED*/
 
 if it is not.  Library code consistently checks for the 'SUPPORTED' macro.
-It does not, and should not, check for the 'NO' macro which will not
-normally be defined even if the feature is not supported.
+It does not, and libpng applications should not, check for the 'NO' macro
+which will not normally be defined even if the feature is not supported.
+The 'NO' macros are only used internally for setting or not setting the
+corresponding 'SUPPORTED' macros.
 
 Compatibility with the old names is provided as follows:
 
@@ -4244,10 +4380,10 @@ application built without PNG_USER_CONFIG defined would see the
 unmodified, default, libpng API and thus would probably fail to link.
 
 These mechanisms still work in the configure build and in any makefile
-build that builds pnglibconf.h although the feature selection macros
+build that builds pnglibconf.h, although the feature selection macros
 have changed somewhat as described above.  In 1.5.0, however, pngusr.h is
 processed only once, when the exported header file pnglibconf.h is built.
-pngconf.h no longer includes pngusr.h, therefore it is ignored after the
+pngconf.h no longer includes pngusr.h, therefore pngusr.h is ignored after the
 build of pnglibconf.h and it is never included in an application build.
 
 The rarely used alternative of adding a list of feature macros to the
@@ -4261,7 +4397,7 @@ scripts/pnglibconf.dfa.  This requires the program awk.  Brian Kernighan
 and all known later implementations (often called by subtly different
 names - nawk and gawk for example) are adequate to build pnglibconf.h.
 The Sun Microsystems (now Oracle) program 'awk' is an earlier version
-and does not work, this may also apply to other systems that have a
+and does not work; this may also apply to other systems that have a
 functioning awk called 'nawk'.
 
 Configuration options are now documented in scripts/pnglibconf.dfa.  This
@@ -4303,8 +4439,8 @@ the libpng bug tracker at
 
 We also accept patches built from the tar or zip distributions, and
 simple verbal discriptions of bug fixes, reported either to the
-SourceForge bug tracker or to the png-mng-implement at lists.sf.net
-mailing list.
+SourceForge bug tracker, to the png-mng-implement at lists.sf.net
+mailing list, or directly to glennrp.
 
 XIII. Coding style
 
@@ -4417,13 +4553,13 @@ Other rules can be inferred by inspecting the libpng source.
 
 XIV. Y2K Compliance in libpng
 
-June 14, 2011
+August 25, 2011
 
 Since the PNG Development group is an ad-hoc body, we can't make
 an official declaration.
 
 This is your unofficial assurance that libpng from version 0.71 and
-upward through 1.5.4beta02 are Y2K compliant.  It is my belief that earlier
+upward through 1.5.5beta06 are Y2K compliant.  It is my belief that earlier
 versions were also Y2K compliant.
 
 Libpng only has three year fields.  One is a 2-byte unsigned integer that

libpng.3

@@ -1,6 +1,6 @@
-.TH LIBPNG 3 "June 14, 2011"
+.TH LIBPNG 3 "August 25, 2011"
 .SH NAME
-libpng \- Portable Network Graphics (PNG) Reference Library 1.5.4beta02
+libpng \- Portable Network Graphics (PNG) Reference Library 1.5.5beta06
 .SH SYNOPSIS
 \fI\fB
 
@@ -128,10 +128,22 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.5.4beta02
 
 \fI\fB
 
-\fBpng_uint_32 png_get_chunk_cache_max (png_const_structp \fIpng_ptr\fP\fB);\fP
+\fBpng_uint_32 png_get_cHRM_XYZ (png_structp \fIpng_ptr,
+
+\fBpng_const_infop \fP\fIinfo_ptr\fP\fB, double \fP\fI*red_X\fP\fB, double \fP\fI*red_Y\fP\fB, double \fI*red_Z,
+
+\fBdouble \fP\fI*green_X\fP\fB, double \fP\fI*green_Y\fP\fB, double \fP\fI*green_Z\fP\fB, double \fI*blue_X,
+
+\fBdouble \fP\fI*blue_Y\fP\fB, double \fI*blue_Z\fP\fB);\fP
 
 \fI\fB
 
+\fBpng_uint_32 png_get_cHRM_XYZ_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_fixed_point \fP\fI*int_red_X\fP\fB, png_fixed_point \fP\fI*int_red_Y\fP\fB, png_fixed_point \fP\fI*int_red_Z\fP\fB, png_fixed_point \fP\fI*int_green_X\fP\fB, png_fixed_point \fP\fI*int_green_Y\fP\fB, png_fixed_point \fP\fI*int_green_Z\fP\fB, png_fixed_point \fP\fI*int_blue_X\fP\fB, png_fixed_point \fP\fI*int_blue_Y\fP\fB, png_fixed_point \fI*int_blue_Z\fP\fB);\fP
+
+\fI\fB
+
+\fBpng_uint_32 png_get_chunk_cache_max (png_const_structp \fIpng_ptr\fP\fB);\fP
+
 \fI\fB
 
 \fBpng_alloc_size_t png_get_chunk_malloc_max (png_const_structp \fIpng_ptr\fP\fB);\fP
@@ -548,6 +560,16 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.5.4beta02
 
 \fI\fB
 
+\fBvoid png_set_cHRM_XYZ (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fP\fIred_X\fP\fB, double \fP\fIred_Y\fP\fB, double \fP\fIred_Z\fP\fB, double \fP\fIgreen_X\fP\fB, double \fIgreen_Y,
+
+\fBdouble \fP\fIgreen_Z\fP\fB, double \fP\fIblue_X\fP\fB, double \fP\fIblue_Y\fP\fB, double \fIblue_Z\fP\fB);\fP
+
+\fI\fB
+
+\fBvoid png_set_cHRM_XYZ_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_fixed_point \fP\fIint_red_X\fP\fB, png_fixed_point \fP\fIint_red_Y\fP\fB, png_fixed_point \fP\fIint_red_Z\fP\fB, png_fixed_point \fP\fIint_green_X\fP\fB, png_fixed_point \fP\fIint_green_Y\fP\fB, png_fixed_point \fP\fIint_green_Z\fP\fB, png_fixed_point \fP\fIint_blue_X\fP\fB, png_fixed_point \fP\fIint_blue_Y\fP\fB, png_fixed_point \fIint_blue_Z\fP\fB);\fP
+
+\fI\fB
+
 \fBvoid png_set_chunk_cache_max (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIuser_chunk_cache_max\fP\fB);\fP
 
 \fI\fB
@@ -672,10 +694,6 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.5.4beta02
 
 \fI\fB
 
-\fBvoid png_set_strip_16 (png_structp \fIpng_ptr\fP\fB);\fP
-
-\fI\fB
-
 \fBvoid png_set_chunk_malloc_max (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIuser_chunk_cache_max\fP\fB);\fP
 
 \fI\fB
@@ -768,6 +786,10 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.5.4beta02
 
 \fI\fB
 
+\fBvoid png_set_scale_16 (png_structp \fIpng_ptr\fP\fB);\fP
+
+\fI\fB
+
 \fBvoid png_set_shift (png_structp \fP\fIpng_ptr\fP\fB, png_color_8p \fItrue_bits\fP\fB);\fP
 
 \fI\fB
@@ -955,7 +977,7 @@ Following is a copy of the libpng-manual.txt file that accompanies libpng.
 .SH LIBPNG.TXT
 libpng-manual.txt - A description on how to use and modify libpng
 
- libpng version 1.5.4beta02 - June 14, 2011
+ libpng version 1.5.5beta06 - August 25, 2011
  Updated and distributed by Glenn Randers-Pehrson
  <glennrp at users.sourceforge.net>
  Copyright (c) 1998-2011 Glenn Randers-Pehrson
@@ -966,7 +988,7 @@ libpng-manual.txt - A description on how to use and modify libpng
 
  Based on:
 
- libpng versions 0.97, January 1998, through 1.5.4beta02 - June 14, 2011
+ libpng versions 0.97, January 1998, through 1.5.5beta06 - August 25, 2011
  Updated and distributed by Glenn Randers-Pehrson
  Copyright (c) 1998-2011 Glenn Randers-Pehrson
 
@@ -1062,7 +1084,8 @@ PNG file.  At one time, the fields of png_info were intended to be
 directly accessible to the user.  However, this tended to cause problems
 with applications using dynamically loaded libraries, and as a result
 a set of interface functions for png_info (the png_get_*() and png_set_*()
-functions) was developed.
+functions) was developed, and direct access to the png_info fields was
+deprecated..
 
 The png_struct structure is the object used by the library to decode a
 single image.  As of 1.5.0 this structure is also not exposed.
@@ -1071,14 +1094,23 @@ Almost all libpng APIs require a pointer to a png_struct as the first argument.
 Many (in particular the png_set and png_get APIs) also require a pointer
 to png_info as the second argument.  Some application visible macros
 defined in png.h designed for basic data access (reading and writing
-integers in the PNG format) break this rule, but it's almost always safe
-to assume that a (png_struct*) has to be passed to call an API function.
+integers in the PNG format) don't take a png_info pointer, but it's almost
+always safe to assume that a (png_struct*) has to be passed to call an API
+function.
+
+You can have more than one png_info structure associated with an image,
+as illustrated in pngtest.c, one for information valid prior to the
+IDAT chunks and another (called "end_info" below) for things after them.
 
 The png.h header file is an invaluable reference for programming with libpng.
 And while I'm on the topic, make sure you include the libpng header file:
 
 #include <png.h>
 
+and also (as of libpng-1.5.0) the zlib header file, if you need it:
+
+#include <zlib.h>
+
 .SS Types
 
 The png.h header file defines a number of integral types used by the
@@ -1092,9 +1124,9 @@ the value by multiplying by 100,000.  As of libpng 1.5.0 a convenience
 macro PNG_FP_1 is defined in png.h along with a type (png_fixed_point)
 which is simply (png_int_32).
 
-All APIs that take (double) arguments also have an matching API that
+All APIs that take (double) arguments also have a matching API that
 takes the corresponding fixed point integer arguments.  The fixed point
-API has the same name as the floating point one with _fixed appended.
+API has the same name as the floating point one with "_fixed" appended.
 The actual range of values permitted in the APIs is frequently less than
 the full range of (png_fixed_point) (-21474 to +21474).  When APIs require
 a non-negative argument the type is recorded as png_uint_32 above.  Consult
@@ -1112,6 +1144,10 @@ preprocessing directives of the form:
     #ifdef PNG_feature_SUPPORTED
     declare-function
     #endif
+    ...
+    #ifdef PNG_feature_SUPPORTED
+    use-function
+    #endif
 
 The library can be built without support for these APIs, although a
 standard build will have all implemented APIs.  Application programs
@@ -1120,7 +1156,7 @@ portability.  From libpng 1.5.0 the feature macros set during the build
 of libpng are recorded in the header file "pnglibconf.h" and this file
 is always included by png.h.
 
-If you don't need to change the library configuration from the default skip to
+If you don't need to change the library configuration from the default, skip to
 the next section ("Reading").
 
 Notice that some of the makefiles in the 'scripts' directory and (in 1.5.0) all
@@ -1152,24 +1188,25 @@ A variety of methods exist to build libpng.  Not all of these support
 reconfiguration of pnglibconf.h.  To reconfigure pnglibconf.h it must either be
 rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand.
 
-Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt and changing
-the lines defining the supported features, paying very close attention to the
-'option' information in scripts/pnglibconf.dfa that describes those features and
-their requirements.  This is easy to get wrong.
+Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt to
+pnglibconf.h and changing the lines defining the supported features, paying
+very close attention to the 'option' information in scripts/pnglibconf.dfa
+that describes those features and their requirements.  This is easy to get
+wrong.
 
 B. Configuration using DFA_XTRA
 
 Rebuilding from pnglibconf.dfa is easy if a functioning 'awk', or a later
 variant such as 'nawk' or 'gawk', is available.  The configure build will
 automatically find an appropriate awk and build pnglibconf.h.
-scripts/pnglibconf.mak contains a set of make rules for doing the same thing if
-configure is not used, and many of the makefiles in the scripts directory use
-this approach.
+The scripts/pnglibconf.mak file contains a set of make rules for doing the
+same thing if configure is not used, and many of the makefiles in the scripts
+directory use this approach.
 
-When rebuilding simply write new file containing changed options and set
+When rebuilding simply write a new file containing changed options and set
 DFA_XTRA to the name of this file.  This causes the build to append the new file
-to the end of scripts/pnglibconf.dfa.  pngusr.dfa should contain lines of the
-following forms:
+to the end of scripts/pnglibconf.dfa.  The pngusr.dfa file should contain lines
+of the following forms:
 
 everything = off
 
@@ -1193,12 +1230,16 @@ source code.  Most of these values have performance implications for the library
 but most of them have no visible effect on the API.  Some can also be overridden
 from the API.
 
+This method of building a customized pnglibconf.h is illustrated in
+contrib/pngminim/*.  See the "$(PNGCONF):" target in the makefile and
+pngusr.dfa in these directories.
+
 C. Configuration using PNG_USR_CONFIG
 
 If -DPNG_USR_CONFIG is added to the CFLAGS when pnglibconf.h is built the file
 pngusr.h will automatically be included before the options in
-scripts/pnglibconf.dfa are processed.  pngusr.h should contain only macro
-definitions turning features on or off or setting settings.
+scripts/pnglibconf.dfa are processed.  Your pngusr.h file should contain only
+macro definitions turning features on or off or setting settings.
 
 Apart from the global setting "everything = off" all the options listed above
 can be set using macros in pngusr.h:
@@ -1229,6 +1270,9 @@ examine the intermediate file pnglibconf.dfn to find the full set of
 dependency information for each setting and option.  Simply locate the
 feature in the file and read the C comments that precede it.
 
+This method is also illustrated in the contrib/pngminim/* makefiles and
+pngusr.h.
+
 .SH III. Reading
 
 We'll now walk you through the possible functions to call when reading
@@ -1512,6 +1556,8 @@ according to the "keep" directive.  If a chunk is named in successive
 instances of png_set_keep_unknown_chunks(), the final instance will
 take precedence.  The IHDR and IEND chunks should not be named in
 chunk_list; if they are, libpng will process them normally anyway.
+If you know that your application will never make use of some particular
+chunks, use PNG_HANDLE_CHUNK_NEVER (or 1) as demonstrated below.
 
 Here is an example of the usage of png_set_keep_unknown_chunks(),
 where the private "vpAg" chunk will later be processed by a user chunk
@@ -1602,13 +1648,14 @@ If you intend to display the PNG or to incorporate it in other image data you
 need to tell libpng information about your display or drawing surface so that
 libpng can convert the values in the image to match the display.
 
-From libpng-1.5.3 this information can be set before reading the PNG file
+From libpng-1.5.4 this information can be set before reading the PNG file
 header.  In earlier versions png_set_gamma() existed but behaved incorrectly if
 called before the PNG file header had been read and png_set_alpha_mode() did not
 exist.
 
-If you need to support versions prior to libpng-1.5.3 test the version number
-and follow the procedures described in the appropriate manual page.
+If you need to support versions prior to libpng-1.5.4 test the version number
+as illustrated below using "PNG_LIBPNG_VER >= 10504" and follow the procedures
+described in the appropriate manual page.
 
 You give libpng the encoding expected by your system expressed as a 'gamma'
 value.  You can also specify a default encoding for the PNG file in
@@ -1628,7 +1675,7 @@ documentation!
 
 Many systems permit the system gamma to be changed via a lookup table in the
 display driver, a few systems, including older Macs, change the response by
-default.  As of 1.5.3 three special values are available to handle common
+default.  As of 1.5.4 three special values are available to handle common
 situations:
 
    PNG_DEFAULT_sRGB: Indicates that the system conforms to the IEC 61966-2-1
@@ -1653,7 +1700,9 @@ Libpng only supports composing onto a single color (using png_set_background;
 see below.)  Otherwise you must do the composition yourself and, in this case,
 you may need to call png_set_alpha_mode:
 
+#if PNG_LIBPNG_VER >= 10504
    png_set_alpha_mode(png_ptr, mode, screen_gamma);
+#endif
 
 The screen_gamma value is the same as the argument to png_set_gamma, however how
 it affects the output depends on the mode.  png_set_alpha_mode() sets the file
@@ -1793,17 +1842,22 @@ format produced by libpng to always have 8-bit or 16-bit components and then
 store the color as an 8-bit or 16-bit color as appropriate.  The color contains
 separate gray and RGB component values, so you can let libpng produce gray or
 RGB output according to the input format, but low bit depth grayscale images
-must always be converted to at least 8-bit format.  (Even low low bit depth
+must always be converted to at least 8-bit format.  (Even though low bit depth
 grayscale images can't have an alpha channel they can have a transparent
 color!)
 
 You set the transforms you need later, either as flags to the high level
 interface or libpng API calls for the low level interface.  For reference the
-settings required are:
+settings and API calls required are:
 
 8-bit values:
-   PNG_TRANSFORM_STRIP_16 | PNG_EXPAND
-   png_set_expand(png_ptr); png_set_strip_16(png_ptr);
+   PNG_TRANSFORM_SCALE_16 | PNG_EXPAND
+   png_set_expand(png_ptr); png_set_scale_16(png_ptr);
+
+   If you must get exactly the same inaccurate results
+   produced by default in versions prior to libpng-1.5.4,
+   use PNG_TRANSFORM_STRIP_16 and png_set_strip_16(png_ptr)
+   instead.
 
 16-bit values:
    PNG_TRANSFORM_EXPAND_16
@@ -1814,9 +1868,9 @@ color data you can add PNG_TRANSFORM_GRAY_TO_RGB or png_set_gray_to_rgb(png_ptr)
 to the list.
 
 Calling png_set_background before the PNG file header is read will not work
-prior to libpng-1.5.3.  Because the failure may result in unexpected warnings or
+prior to libpng-1.5.4.  Because the failure may result in unexpected warnings or
 errors it is therefore much safer to call png_set_background after the head has
-been read.  Unfortunately this means that prior to libpng-1.5.3 it cannot be
+been read.  Unfortunately this means that prior to libpng-1.5.4 it cannot be
 used with the high level interface.
 
 .SS The high-level read interface
@@ -1828,8 +1882,10 @@ the entire image into memory, and (b) the input transformations
 you want to do are limited to the following set:
 
     PNG_TRANSFORM_IDENTITY      No transformation
-    PNG_TRANSFORM_STRIP_16      Strip 16-bit samples to
-                                8-bit
+    PNG_TRANSFORM_SCALE_16      Strip 16-bit samples to
+                                8-bit accurately
+    PNG_TRANSFORM_STRIP_16      Chop 16-bit samples to
+                                8-bit less accurately
     PNG_TRANSFORM_STRIP_ALPHA   Discard the alpha channel
     PNG_TRANSFORM_PACKING       Expand 1, 2 and 4-bit
                                 samples to bytes
@@ -1923,9 +1979,9 @@ for use in later transformations.  Important information copied in is:
 1) The PNG file gamma from the gAMA chunk.  This overwrites the default value
 provided by an earlier call to png_set_gamma or png_set_alpha_mode.
 
-2) Prior to libpng-1.5.3 the background color from a bKGd chunk.  This
+2) Prior to libpng-1.5.4 the background color from a bKGd chunk.  This
 damages the information provided by an earlier call to png_set_background
-resulting in expected behavior.  Libpng-1.5.3 no longer does this.
+resulting in unexpected behavior.  Libpng-1.5.4 no longer does this.
 
 3) The number of significant bits in each component value.  Libpng uses this to
 optimize gamma handling by reducing the internal lookup table sizes.
@@ -2063,6 +2119,28 @@ pointer into the info_ptr is returned for any complex types.
     int_file_gamma - 100,000 times the gamma at which the
                      file is written
 
+    png_get_cHRM(png_ptr, info_ptr,  &white_x, &white_y, &red_x, &red_y,
+                     &green_x, &green_y, &blue_x, &blue_y)
+    png_get_cHRM_XYZ(png_ptr, info_ptr, &red_X, &red_Y, &red_Z, &green_X,
+                     &green_Y, &green_Z, &blue_X, &blue_Y, &blue_Z)
+    png_get_cHRM_fixed(png_ptr, info_ptr, &int_white_x, &int_white_y,
+                     &int_red_x, &int_red_y, &int_green_x, &int_green_y,
+                     &int_blue_x, &int_blue_y)
+    png_get_cHRM_XYZ_fixed(png_ptr, info_ptr, &int_red_X, &int_red_Y,
+                     &int_red_Z, &int_green_X, &int_green_Y, &int_green_Z,
+                     &int_blue_X, &int_blue_Y, &int_blue_Z)
+
+    {white,red,green,blue}_{x,y}
+                     A color space encoding specified using the chromaticities
+                     of the end points and the white point. (PNG_INFO_cHRM)
+
+    {red,green,blue}_{X,Y,Z}
+                     A color space encoding specified using the encoding end
+                     points - the CIE tristimulus specification of the intended
+                     color of the red, green and blue channels in the PNG RGB
+                     data.  The white point is simply the sum of the three end
+                     points. (PNG_INFO_cHRM)
+
     png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
 
     file_srgb_intent - the rendering intent (PNG_INFO_sRGB)
@@ -2121,7 +2199,8 @@ pointer into the info_ptr is returned for any complex types.
 
     png_get_bKGD(png_ptr, info_ptr, &background);
 
-    background     - background color (PNG_VALID_bKGD)
+    background     - background color (of type
+                     png_color_16p) (PNG_VALID_bKGD)
                      valid 16-bit red, green and blue
                      values, regardless of color_type
 
@@ -2160,6 +2239,8 @@ pointer into the info_ptr is returned for any complex types.
     Note that the itxt_length, lang, and lang_key
     members of the text_ptr structure only exist
     when the library is built with iTXt chunk support.
+    Prior to libpng-1.4.0, the default build was
+    without iTXt chunk support.
 
     num_text       - number of comments (same as
                      num_comments; you can put NULL here
@@ -2184,10 +2265,10 @@ pointer into the info_ptr is returned for any complex types.
        &unit_type);
 
     offset_x       - positive offset from the left edge
-                     of the screen
+                     of the screen (can be negative)
 
     offset_y       - positive offset from the top edge
-                     of the screen
+                     of the screen (can be negative)
 
     unit_type      - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
 
@@ -2219,6 +2300,7 @@ pointer into the info_ptr is returned for any complex types.
     unit        - physical scale units (an integer)
 
     width       - width of a pixel in physical scale units
+                  (expressed as a string)
 
     height      - height of a pixel in physical scale units
                  (width and height are strings like "2.54")
@@ -2241,6 +2323,12 @@ pointer into the info_ptr is returned for any complex types.
     chunks were read from the PNG file or inserted with the
     png_set_unknown_chunks() function.
 
+    The value of "location" is a bitwise "or" of
+
+         PNG_HAVE_IHDR  (0x01)
+         PNG_HAVE_PLTE  (0x02)
+         PNG_AFTER_IDAT (0x08)
+
 The data from the pHYs chunk can be retrieved in several convenient
 forms:
 
@@ -2354,12 +2442,12 @@ byte, unless png_set_packing() is called.  8-bit RGB data will be stored
 in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha()
 is called to insert filler bytes, either before or after each RGB triplet.
 16-bit RGB data will be returned RRGGBB RRGGBB, with the most significant
-byte of the color value first, unless png_set_strip_16() is called to
+byte of the color value first, unless png_set_scale_16() is called to
 transform it to regular RGB RGB triplets, or png_set_filler() or
 png_set_add alpha() is called to insert filler bytes, either before or
 after each RRGGBB triplet.  Similarly, 8-bit or 16-bit grayscale data can
-be modified with
-png_set_filler(), png_set_add_alpha(), or png_set_strip_16().
+be modified with png_set_filler(), png_set_add_alpha(), png_set_strip_16(),
+or png_set_scale_16().
 
 The following code transforms grayscale images of less than 8 to 8 bits,
 changes paletted images to RGB, and adds a full alpha channel if there is
@@ -2385,7 +2473,7 @@ As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was
 added.  It expands the sample depth without changing tRNS to alpha.
 
 As of libpng version 1.5.2, png_set_expand_16() was added.  It behaves as
-png_set_expand(), however, the resultant channels have 16 bits rather than 8.
+png_set_expand(); however, the resultant channels have 16 bits rather than 8.
 Use this when the output color or gray channels are made linear to avoid fairly
 severe accuracy loss.
 
@@ -2396,7 +2484,14 @@ PNG can have files with 16 bits per channel.  If you only can handle
 8 bits per channel, this will strip the pixels down to 8-bit.
 
     if (bit_depth == 16)
+#if PNG_LIBPNG_VER >= 10504
+       png_set_scale_16(png_ptr);
+#else
        png_set_strip_16(png_ptr);
+#endif
+
+(The more accurate "png_set_scale_16()" API became available in libpng version
+1.5.4).
 
 If you need to process the alpha channel on the image separately from the image
 data (for example if you convert it to a bitmap mask) it is possible to have
@@ -2574,31 +2669,41 @@ It will return a png_byte that is zero if the image was gray or
 will be silently converted to grayscale, using the green channel
 data for sBIT, regardless of the error_action setting.
 
-The default values come from the PNG file cHRM chunk if present, otherwise the
+The default values come from the PNG file cHRM chunk if present; otherwise, the
 defaults correspond to the ITU-R recommendation 709, and also the sRGB color
 space, as recommended in the Charles Poynton's Colour FAQ,
 <http://www.poynton.com/>, in section 9:
 
    <http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9>
 
+    Y = 0.2126 * R + 0.7152 * G + 0.0722 * B
+
+Previous versions of this document, 1998 through 2002, recommended a slightly
+different formula:
+
     Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
 
+Libpng uses an integer approximation:
+
+    Y = (6968 * R + 23434 * G + 2366 * B)/32768
+
 The calculation is done in a linear colorspace, if the image gamma
 can be determined.
 
-The png_set_background() function has been described already, it tells libpng to
+The png_set_background() function has been described already; it tells libpng to
 composite images with alpha or simple transparency against the supplied
 background color.  For compatibility with versions of libpng earlier than
-libpng-1.5.3 it is recommended that you call the function after reading the file
+libpng-1.5.4 it is recommended that you call the function after reading the file
 header, even if you don't want to use the color in a bKGD chunk, if one exists.
 
 If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid),
 you may use this color, or supply another color more suitable for
 the current display (e.g., the background color from a web page).  You
 need to tell libpng how the color is represented, both the format of the
-component values in the color (the number of bits) and the gamme encoding of the
+component values in the color (the number of bits) and the gamma encoding of the
 color.  The function takes two arguments, background_gamma_mode and need_expand
-to convey this information, however only two combinations are like to be useful:
+to convey this information, however only two combinations are likely to be
+useful:
 
     png_color_16 my_background;
     png_color_16p image_background;
@@ -2610,7 +2715,6 @@ to convey this information, however only two combinations are like to be useful:
        png_set_background(png_ptr, &my_background,
            PNG_BACKGROUND_GAMMA_SCREEN, 0/*do not expand*/, 1);
 
-
 The second call was described above - my_background is in the format of the
 final, display, output produced by libpng.  Because you now know the format of
 the PNG it is possible to avoid the need to choose either 8-bit or 16-bit
@@ -2626,7 +2730,7 @@ image_background->gray.
 
 If you didn't call png_set_gamma() before reading the file header, for example
 if you need your code to remain compatible with older versions of libpng prior
-to libpng-1.5.3, this is the place to call it.
+to libpng-1.5.4, this is the place to call it.
 
 Do not call it if you called png_set_alpha_mode(); doing so will damage the
 settings put in place by png_set_alpha_mode().  (If png_set_alpha_mode() is
@@ -2649,9 +2753,9 @@ file has more entries then will fit on your screen, png_set_quantize()
 will do that.  Note that this is a simple match quantization that merely
 finds the closest color available.  This should work fairly well with
 optimized palettes, but fairly badly with linear color cubes.  If you
-pass a palette that is larger then maximum_colors, the file will
+pass a palette that is larger than maximum_colors, the file will
 reduce the number of colors in the palette so it will fit into
-maximum_colors.  If there is a histogram, it will use it to make
+maximum_colors.  If there is a histogram, libpng will use it to make
 more intelligent choices when reducing the palette.  If there is no
 histogram, it may not do as good a job.
 
@@ -2723,7 +2827,7 @@ after all of the other transformations have been processed.  Take care with
 interlaced images if you do the interlace yourself - the width of the row is the
 width in 'row_info', not the overall image width.
 
-If supported libpng provides two information routines that you can use to find
+If supported, libpng provides two information routines that you can use to find
 where you are in processing the image:
 
    png_get_current_pass_number(png_structp png_ptr);
@@ -3587,6 +3691,28 @@ width, height, bit_depth, and color_type must be the same in each call.
     int_file_gamma - 100,000 times the gamma at which
                      the image was created
 
+    png_set_cHRM(png_ptr, info_ptr,  white_x, white_y, red_x, red_y,
+                     green_x, green_y, blue_x, blue_y)
+    png_set_cHRM_XYZ(png_ptr, info_ptr, red_X, red_Y, red_Z, green_X,
+                     green_Y, green_Z, blue_X, blue_Y, blue_Z)
+    png_set_cHRM_fixed(png_ptr, info_ptr, int_white_x, int_white_y,
+                     int_red_x, int_red_y, int_green_x, int_green_y,
+                     int_blue_x, int_blue_y)
+    png_set_cHRM_XYZ_fixed(png_ptr, info_ptr, int_red_X, int_red_Y,
+                     int_red_Z, int_green_X, int_green_Y, int_green_Z,
+                     int_blue_X, int_blue_Y, int_blue_Z)
+
+    {white,red,green,blue}_{x,y}
+                     A color space encoding specified using the chromaticities
+                     of the end points and the white point.
+
+    {red,green,blue}_{X,Y,Z}
+                     A color space encoding specified using the encoding end
+                     points - the CIE tristimulus specification of the intended
+                     color of the red, green and blue channels in the PNG RGB
+                     data.  The white point is simply the sum of the three end
+                     points.
+
     png_set_sRGB(png_ptr, info_ptr, srgb_intent);
 
     srgb_intent    - the rendering intent
@@ -3647,14 +3773,14 @@ width, height, bit_depth, and color_type must be the same in each call.
     trans_alpha    - array of alpha (transparency)
                      entries for palette (PNG_INFO_tRNS)
 
+    num_trans      - number of transparent entries
+                     (PNG_INFO_tRNS)
+
     trans_color    - graylevel or color sample values
                      (in order red, green, blue) of the
                      single transparent color for
                      non-paletted images (PNG_INFO_tRNS)
 
-    num_trans      - number of transparent entries
-                     (PNG_INFO_tRNS)
-
     png_set_hIST(png_ptr, info_ptr, hist);
 
     hist           - histogram of palette (array of
@@ -3667,7 +3793,8 @@ width, height, bit_depth, and color_type must be the same in each call.
 
     png_set_bKGD(png_ptr, info_ptr, background);
 
-    background     - background color (PNG_VALID_bKGD)
+    background     - background color (of type
+                     png_color_16p) (PNG_VALID_bKGD)
 
     png_set_text(png_ptr, info_ptr, text_ptr, num_text);
 
@@ -3694,6 +3821,8 @@ width, height, bit_depth, and color_type must be the same in each call.
     Note that the itxt_length, lang, and lang_key
     members of the text_ptr structure only exist
     when the library is built with iTXt chunk support.
+    Prior to libpng-1.4.0 the library was built by default
+    without iTXt support.
 
     num_text       - number of comments
 
@@ -3743,6 +3872,7 @@ width, height, bit_depth, and color_type must be the same in each call.
     unit        - physical scale units (an integer)
 
     width       - width of a pixel in physical scale units
+                  expressed as a string
 
     height      - height of a pixel in physical scale units
                  (width and height are strings like "2.54")
@@ -3784,7 +3914,7 @@ Because tEXt and zTXt chunks don't have a language field, if you
 specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt
 any language code or translated keyword will not be written out.
 
-Until text gets around 1000 bytes, it is not worth compressing it.
+Until text gets around a few hundred bytes, it is not worth compressing it.
 After the text has been written out to the file, the compression type
 is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR,
 so that it isn't written out again at the end (in case you are calling
@@ -4394,7 +4524,8 @@ However, there are some uncertainties about the status of local variables
 after a longjmp, so the user may want to be careful about doing anything
 after setjmp returns non-zero besides returning itself.  Consult your
 compiler documentation for more details.  For an alternative approach, you
-may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net).
+may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net),
+which is illustrated in pngvalid.c and in contrib/visupng.
 
 .SS Custom chunks
 
@@ -4412,8 +4543,11 @@ and look at how other chunks were designed, so you can do things
 similarly.  Second, check out the sections of libpng that read and
 write chunks.  Try to find a chunk that is similar to yours and use
 it as a template.  More details can be found in the comments inside
-the code.  It is best to handle unknown chunks in a generic method,
-via callback functions, instead of by modifying libpng functions.
+the code.  It is best to handle private or unknown chunks in a generic method,
+via callback functions, instead of by modifying libpng functions. This
+is illustrated in pngtest.c, which uses a callback function to handle a
+private "vpAg" chunk and the new "sTER" chunk, which are both unknown to
+libpng.
 
 If you wish to write your own transformation for the data, look through
 the part of the code that does the transformations, and check out some of
@@ -4441,8 +4575,8 @@ defined, and FAR gets defined to far in pngconf.h, and you should be
 all set.  Everything in the library (except for zlib's structure) is
 expecting far data.  You must use the typedefs with the p or pp on
 the end for pointers (or at least look at them and be careful).  Make
-note that the rows of data are defined as png_bytepp, which is an
-unsigned char far * far *.
+note that the rows of data are defined as png_bytepp, which is
+an "unsigned char far * far *".
 
 .SS Configuring for gui/windowing platforms:
 
@@ -4460,7 +4594,11 @@ or delete an include, this is the place to do it.
 The includes that are not needed outside libpng are placed in pngpriv.h,
 which is only used by the routines inside libpng itself.
 The files in libpng proper only include pngpriv.h and png.h, which
-in turn includes pngconf.h.
+%14%in turn includes pngconf.h.
+in turn includes pngconf.h and, as of libpng-1.5.0, pnglibconf.h.
+As of libpng-1.5.0, pngpriv.h also includes three other private header
+files, pngstruct.h, pnginfo.h, and pngdebug.h, which contain material
+that previously appeared in the public headers.
 
 .SS Configuring zlib:
 
@@ -4502,8 +4640,28 @@ zlib.h for more information on what these mean.
         window_bits);
 
     png_set_compression_method(png_ptr, method);
+
     png_set_compression_buffer_size(png_ptr, size);
 
+As of libpng version 1.5.4, additional APIs became
+available to set these separately for non-IDAT
+compressed chunks such as zTXt, iTXt, and iCCP:
+
+    #include zlib.h
+    #if PNG_LIBPNG_VER <= 10504
+    png_set_text_compression_level(png_ptr, level);
+
+    png_set_text_compression_mem_level(png_ptr, level);
+
+    png_set_text_compression_strategy(png_ptr,
+        strategy);
+
+    png_set_text_compression_window_bits(png_ptr,
+        window_bits);
+
+    png_set_text_compression_method(png_ptr, method);
+    #endif
+
 .SS Controlling row filtering
 
 If you want to control whether libpng uses filtering or not, which
@@ -4609,8 +4767,8 @@ capability, which you'll still have).
 All the reading and writing specific code are in separate files, so the
 linker should only grab the files it needs.  However, if you want to
 make sure, or if you are building a stand alone library, all the
-reading files start with pngr and all the writing files start with
-pngw.  The files that don't match either (like png.c, pngtrans.c, etc.)
+reading files start with "pngr" and all the writing files start with "pngw".
+The files that don't match either (like png.c, pngtrans.c, etc.)
 are used for both reading and writing, and always need to be included.
 The progressive reader is in pngpread.c
 
@@ -4988,7 +5146,6 @@ absolutely necessary) interlace an image.
 
 libpng 1.5.0 adds an API png_longjmp(png_ptr, value).  This API calls
 the application-provided png_longjmp_ptr on the internal, but application
-initialized, jmpbuf.  It is provided as a convenience to avoid the need
 initialized, longjmp buffer.  It is provided as a convenience to avoid
 the need to use the png_jmpbuf macro, which had the unnecessary side
 effect of resetting the internal png_longjmp_ptr value.
@@ -5045,20 +5202,20 @@ PNG_NO_USE_READ_MACROS before including png.h.  Notice that this is
 only supported from 1.5.0 -defining PNG_NO_USE_READ_MACROS prior to 1.5.0
  will lead to a link failure.
 
-Prior to libpng-1.5.3, the zlib compressor used the same set of parameters
+Prior to libpng-1.5.4, the zlib compressor used the same set of parameters
 when compressing the IDAT data and textual data such as zTXt and iCCP.
-In libpng-1.5.3 we reinitialized the zlib stream for each type of data.
+In libpng-1.5.4 we reinitialized the zlib stream for each type of data.
 We added five png_set_text_*() functions for setting the parameters to
 use with textual data.
 
-Prior to libpng-1.5.3, the PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
+Prior to libpng-1.5.4, the PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
 option was off by default, and slightly inaccurate scaling occurred.
-This option can no longer be turned off, and 16-to-8 scaling is always
-accurate.  This change will result in some different results while
-reading 16-bit images, with none of the pixels being off-by-one any
-longer (see Clause 13.12 of the PNG specification).
+This option can no longer be turned off, and the choice of accurate
+or inaccurate 16-to-8 scaling is by using the new png_set_scale_16_to_8()
+API for accurate scaling or the old png_set_strip_16_to_8() API for simple
+chopping.
 
-Prior to libpng-1.5.3, the png_set_user_limits() function could only be
+Prior to libpng-1.5.4, the png_set_user_limits() function could only be
 used to reduce the width and height limits from the value of
 PNG_USER_WIDTH_MAX and PNG_USER_HEIGHT_MAX, although this document said
 that it could be used to override them.  Now this function will reduce or
@@ -5067,9 +5224,9 @@ increase the limits.
 B. Changes to the build and configuration of libpng
 
 Details of internal changes to the library code can be found in the CHANGES
-file.  These will be of no concern to the vast majority of library users or
-builders, however the few who configure libpng to a non-default feature
-set may need to change how this is done.
+file and in the GIT repository logs.  These will be of no concern to the vast
+majority of library users or builders, however the few who configure libpng
+to a non-default feature set may need to change how this is done.
 
 There should be no need for library builders to alter build scripts if
 these use the distributed build support - configure or the makefiles -
@@ -5078,14 +5235,14 @@ to build pnglibconf.h where the corresponding makefile does not do so.
 
 Building libpng with a non-default configuration has changed completely.
 The old method using pngusr.h should still work correctly even though the
-way pngusr.h is used in the build has been changed, however library
+way pngusr.h is used in the build has been changed; however, library
 builders will probably want to examine the changes to take advantage of
 new capabilities and to simplify their build system.
 
 B.1 Specific changes to library configuration capabilities
 
 The library now supports a complete fixed point implementation and can
-thus be used on systems which have no floating point support or very
+thus be used on systems that have no floating point support or very
 limited or slow support.  Previously gamma correction, an essential part
 of complete PNG support, required reasonably fast floating point.
 
@@ -5101,14 +5258,14 @@ pnglibconf.h
 As part of this the mechanism used to choose procedure call standards on
 those systems that allow a choice has been changed.  At present this only
 affects certain Microsoft (DOS, Windows) and IBM (OS/2) operating systems
-running on Intel processors.  As before PNGAPI is defined where required
+running on Intel processors.  As before, PNGAPI is defined where required
 to control the exported API functions; however, two new macros, PNGCBAPI
 and PNGCAPI, are used instead for callback functions (PNGCBAPI) and
 (PNGCAPI) for functions that must match a C library prototype (currently
 only png_longjmp_ptr, which must match the C longjmp function.)  The new
 approach is documented in pngconf.h
 
-Despite these changes libpng 1.5.0 only supports the native C function
+Despite these changes, libpng 1.5.0 only supports the native C function
 calling standard on those platforms tested so far (__cdecl on Microsoft
 Windows).  This is because the support requirements for alternative
 calling conventions seem to no longer exist.  Developers who find it
@@ -5141,8 +5298,10 @@ if the feature is supported or:
 /*#undef PNG_feature_SUPPORTED*/
 
 if it is not.  Library code consistently checks for the 'SUPPORTED' macro.
-It does not, and should not, check for the 'NO' macro which will not
-normally be defined even if the feature is not supported.
+It does not, and libpng applications should not, check for the 'NO' macro
+which will not normally be defined even if the feature is not supported.
+The 'NO' macros are only used internally for setting or not setting the
+corresponding 'SUPPORTED' macros.
 
 Compatibility with the old names is provided as follows:
 
@@ -5199,10 +5358,10 @@ application built without PNG_USER_CONFIG defined would see the
 unmodified, default, libpng API and thus would probably fail to link.
 
 These mechanisms still work in the configure build and in any makefile
-build that builds pnglibconf.h although the feature selection macros
+build that builds pnglibconf.h, although the feature selection macros
 have changed somewhat as described above.  In 1.5.0, however, pngusr.h is
 processed only once, when the exported header file pnglibconf.h is built.
-pngconf.h no longer includes pngusr.h, therefore it is ignored after the
+pngconf.h no longer includes pngusr.h, therefore pngusr.h is ignored after the
 build of pnglibconf.h and it is never included in an application build.
 
 The rarely used alternative of adding a list of feature macros to the
@@ -5216,7 +5375,7 @@ scripts/pnglibconf.dfa.  This requires the program awk.  Brian Kernighan
 and all known later implementations (often called by subtly different
 names - nawk and gawk for example) are adequate to build pnglibconf.h.
 The Sun Microsystems (now Oracle) program 'awk' is an earlier version
-and does not work, this may also apply to other systems that have a
+and does not work; this may also apply to other systems that have a
 functioning awk called 'nawk'.
 
 Configuration options are now documented in scripts/pnglibconf.dfa.  This
@@ -5258,8 +5417,8 @@ the libpng bug tracker at
 
 We also accept patches built from the tar or zip distributions, and
 simple verbal discriptions of bug fixes, reported either to the
-SourceForge bug tracker or to the png-mng-implement at lists.sf.net
-mailing list.
+SourceForge bug tracker, to the png-mng-implement at lists.sf.net
+mailing list, or directly to glennrp.
 
 .SH XIII. Coding style
 
@@ -5372,13 +5531,13 @@ Other rules can be inferred by inspecting the libpng source.
 
 .SH XIV. Y2K Compliance in libpng
 
-June 14, 2011
+August 25, 2011
 
 Since the PNG Development group is an ad-hoc body, we can't make
 an official declaration.
 
 This is your unofficial assurance that libpng from version 0.71 and
-upward through 1.5.4beta02 are Y2K compliant.  It is my belief that earlier
+upward through 1.5.5beta06 are Y2K compliant.  It is my belief that earlier
 versions were also Y2K compliant.
 
 Libpng only has three year fields.  One is a 2-byte unsigned integer that
@@ -5571,7 +5730,10 @@ the first widely used release:
  1.5.3rc01-02        15    10503  15.so.15.3[.0]
  1.5.3beta11         15    10503  15.so.15.3[.0]
  1.5.3 [omitted]
- 1.5.4beta01-02      15    10504  15.so.15.4[.0]
+ 1.5.4beta01-08      15    10504  15.so.15.4[.0]
+ 1.5.4rc01           15    10504  15.so.15.4[.0]
+ 1.5.4               15    10504  15.so.15.4[.0]
+ 1.5.5beta01-06      15    10505  15.so.15.5[.0]
 
 Henceforth the source version will match the shared-library minor
 and patch numbers; the shared-library major version number will be
@@ -5628,7 +5790,7 @@ possible without all of you.
 
 Thanks to Frank J. T. Wojcik for helping with the documentation.
 
-Libpng version 1.5.4beta02 - June 14, 2011:
+Libpng version 1.5.5beta06 - August 25, 2011:
 Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
 Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).
 
@@ -5651,7 +5813,7 @@ this sentence.
 
 This code is released under the libpng license.
 
-libpng versions 1.2.6, August 15, 2004, through 1.5.4beta02, June 14, 2011, are
+libpng versions 1.2.6, August 15, 2004, through 1.5.5beta06, August 25, 2011, are
 Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are
 distributed according to the same disclaimer and license as libpng-1.2.5
 with the following individual added to the list of Contributing Authors
@@ -5750,7 +5912,7 @@ certification mark of the Open Source Initiative.
 
 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-June 14, 2011
+August 25, 2011
 
 .\" end of man page
 

libpngpf.3

@@ -1,6 +1,6 @@
-.TH LIBPNGPF 3 "June 14, 2011"
+.TH LIBPNGPF 3 "August 25, 2011"
 .SH NAME
-libpng \- Portable Network Graphics (PNG) Reference Library 1.5.4beta02
+libpng \- Portable Network Graphics (PNG) Reference Library 1.5.5beta06
 (private functions)
 .SH SYNOPSIS
 \fB#include \fI"pngpriv.h"

png.5

@@ -1,4 +1,4 @@
-.TH PNG 5 "June 14, 2011"
+.TH PNG 5 "August 25, 2011"
 .SH NAME
 png \- Portable Network Graphics (PNG) format
 .SH DESCRIPTION

png.c

@@ -1,7 +1,7 @@
 
 /* png.c - location for general purpose libpng functions
  *
- * Last changed in libpng 1.5.4 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.5 [(PENDING RELEASE)]
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -14,7 +14,7 @@
 #include "pngpriv.h"
 
 /* Generate a compiler error if there is an old png.h in the search path. */
-typedef png_libpng_version_1_5_4beta02 Your_png_h_is_not_version_1_5_4beta02;
+typedef png_libpng_version_1_5_5beta06 Your_png_h_is_not_version_1_5_5beta06;
 
 /* Tells libpng that we have already handled the first "num_bytes" bytes
  * of the PNG file signature.  If the PNG data is embedded into another
@@ -43,7 +43,7 @@ png_set_sig_bytes(png_structp png_ptr, int num_bytes)
  * can simply check the remaining bytes for extra assurance.  Returns
  * an integer less than, equal to, or greater than zero if sig is found,
  * respectively, to be less than, to match, or be greater than the correct
- * PNG signature (this is the same behaviour as strcmp, memcmp, etc).
+ * PNG signature (this is the same behavior as strcmp, memcmp, etc).
  */
 int PNGAPI
 png_sig_cmp(png_const_bytep sig, png_size_t start, png_size_t num_to_check)
@@ -542,8 +542,8 @@ png_get_io_ptr(png_structp png_ptr)
 /* Initialize the default input/output functions for the PNG file.  If you
  * use your own read or write routines, you can call either png_set_read_fn()
  * or png_set_write_fn() instead of png_init_io().  If you have defined
- * PNG_NO_STDIO, you must use a function of your own because "FILE *" isn't
- * necessarily available.
+ * PNG_NO_STDIO or otherwise disabled PNG_STDIO_SUPPORTED, you must use a
+ * function of your own because "FILE *" isn't necessarily available.
  */
 void PNGAPI
 png_init_io(png_structp png_ptr, png_FILE_p fp)
@@ -617,13 +617,13 @@ png_get_copyright(png_const_structp png_ptr)
 #else
 #  ifdef __STDC__
    return PNG_STRING_NEWLINE \
-     "libpng version 1.5.4beta02 - June 14, 2011" PNG_STRING_NEWLINE \
+     "libpng version 1.5.5beta06 - August 25, 2011" PNG_STRING_NEWLINE \
      "Copyright (c) 1998-2011 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \
      "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
      "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
      PNG_STRING_NEWLINE;
 #  else
-      return "libpng version 1.5.4beta02 - June 14, 2011\
+      return "libpng version 1.5.5beta06 - August 25, 2011\
       Copyright (c) 1998-2011 Glenn Randers-Pehrson\
       Copyright (c) 1996-1997 Andreas Dilger\
       Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
@@ -713,18 +713,9 @@ png_access_version_number(void)
 
 
 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
-#  ifdef PNG_SIZE_T
-/* Added at libpng version 1.2.6 */
-   PNG_EXTERN png_size_t PNGAPI png_convert_size PNGARG((size_t size));
-png_size_t PNGAPI
-png_convert_size(size_t size)
-{
-   if (size > (png_size_t)-1)
-      PNG_ABORT();  /* We haven't got access to png_ptr, so no png_error() */
-
-   return ((png_size_t)size);
-}
-#  endif /* PNG_SIZE_T */
+/* png_convert_size: a PNGAPI but no longer in png.h, so deleted
+ * at libpng 1.5.5!
+ */
 
 /* Added at libpng version 1.2.34 and 1.4.0 (moved from pngset.c) */
 #  ifdef PNG_CHECK_cHRM_SUPPORTED
@@ -798,6 +789,326 @@ png_check_cHRM_fixed(png_structp png_ptr,
 }
 #  endif /* PNG_CHECK_cHRM_SUPPORTED */
 
+#ifdef PNG_cHRM_SUPPORTED
+/* Added at libpng-1.5.5 to support read and write of true CIEXYZ values for
+ * cHRM, as opposed to using chromaticities.  These internal APIs return
+ * non-zero on a parameter error.  The X, Y and Z values are required to be
+ * positive and less than 1.0.
+ */
+int png_xy_from_XYZ(png_xy *xy, png_XYZ XYZ)
+{
+   png_int_32 d, dwhite, whiteX, whiteY;
+
+   d = XYZ.redX + XYZ.redY + XYZ.redZ;
+   if (!png_muldiv(&xy->redx, XYZ.redX, PNG_FP_1, d)) return 1;
+   if (!png_muldiv(&xy->redy, XYZ.redY, PNG_FP_1, d)) return 1;
+   dwhite = d;
+   whiteX = XYZ.redX;
+   whiteY = XYZ.redY;
+
+   d = XYZ.greenX + XYZ.greenY + XYZ.greenZ;
+   if (!png_muldiv(&xy->greenx, XYZ.greenX, PNG_FP_1, d)) return 1;
+   if (!png_muldiv(&xy->greeny, XYZ.greenY, PNG_FP_1, d)) return 1;
+   dwhite += d;
+   whiteX += XYZ.greenX;
+   whiteY += XYZ.greenY;
+
+   d = XYZ.blueX + XYZ.blueY + XYZ.blueZ;
+   if (!png_muldiv(&xy->bluex, XYZ.blueX, PNG_FP_1, d)) return 1;
+   if (!png_muldiv(&xy->bluey, XYZ.blueY, PNG_FP_1, d)) return 1;
+   dwhite += d;
+   whiteX += XYZ.blueX;
+   whiteY += XYZ.blueY;
+
+   /* The reference white is simply the same of the end-point (X,Y,Z) vectors,
+    * thus:
+    */
+   if (!png_muldiv(&xy->whitex, whiteX, PNG_FP_1, dwhite)) return 1;
+   if (!png_muldiv(&xy->whitey, whiteY, PNG_FP_1, dwhite)) return 1;
+
+   return 0;
+}
+
+int png_XYZ_from_xy(png_XYZ *XYZ, png_xy xy)
+{
+   png_fixed_point red_inverse, green_inverse, blue_scale;
+   png_fixed_point left, right, denominator;
+
+   /* Check xy and, implicitly, z.  Note that wide gamut color spaces typically
+    * have end points with 0 tristimulus values (these are impossible end
+    * points, but they are used to cover the possible colors.)
+    */
+   if (xy.redx < 0 || xy.redx > PNG_FP_1) return 1;
+   if (xy.redy < 0 || xy.redy > PNG_FP_1-xy.redx) return 1;
+   if (xy.greenx < 0 || xy.greenx > PNG_FP_1) return 1;
+   if (xy.greeny < 0 || xy.greeny > PNG_FP_1-xy.greenx) return 1;
+   if (xy.bluex < 0 || xy.bluex > PNG_FP_1) return 1;
+   if (xy.bluey < 0 || xy.bluey > PNG_FP_1-xy.bluex) return 1;
+   if (xy.whitex < 0 || xy.whitex > PNG_FP_1) return 1;
+   if (xy.whitey < 0 || xy.whitey > PNG_FP_1-xy.whitex) return 1;
+
+   /* The reverse calculation is more difficult because the original tristimulus
+    * value had 9 independent values (red,green,blue)x(X,Y,Z) however only 8
+    * derived values were recorded in the cHRM chunk;
+    * (red,green,blue,white)x(x,y).  This loses one degree of freedom and
+    * therefore an arbitrary ninth value has to be introduced to undo the
+    * original transformations.
+    *
+    * Think of the original end-points as points in (X,Y,Z) space.  The
+    * chromaticity values (c) have the property:
+    *
+    *           C
+    *   c = ---------
+    *       X + Y + Z
+    *
+    * For each c (x,y,z) from the corresponding original C (X,Y,Z).  Thus the
+    * three chromaticity values (x,y,z) for each end-point obey the
+    * relationship:
+    *
+    *   x + y + z = 1
+    *
+    * This describes the plane in (X,Y,Z) space that intersects each axis at the
+    * value 1.0; call this the chromaticity plane.  Thus the chromaticity
+    * calculation has scaled each end-point so that it is on the x+y+z=1 plane
+    * and chromaticity is the intersection of the vector from the origin to the
+    * (X,Y,Z) value with the chromaticity plane.
+    *
+    * To fully invert the chromaticity calculation we would need the three
+    * end-point scale factors, (red-scale, green-scale, blue-scale), but these
+    * were not recorded.  Instead we calculated the reference white (X,Y,Z) and
+    * recorded the chromaticity of this.  The reference white (X,Y,Z) would have
+    * given all three of the scale factors since:
+    *
+    *    color-C = color-c * color-scale
+    *    white-C = red-C + green-C + blue-C
+    *            = red-c*red-scale + green-c*green-scale + blue-c*blue-scale
+    *
+    * But cHRM records only white-x and white-y, so we have lost the white scale
+    * factor:
+    *
+    *    white-C = white-c*white-scale
+    *
+    * To handle this the inverse transformation makes an arbitrary assumption
+    * about white-scale:
+    *
+    *    Assume: white-Y = 1.0
+    *    Hence:  white-scale = 1/white-y
+    *    Or:     red-Y + green-Y + blue-Y = 1.0
+    *
+    * Notice the last statement of the assumption gives an equation in three of
+    * the nine values we want to calculate.  8 more equations come from the
+    * above routine as summarised at the top above (the chromaticity
+    * calculation):
+    *
+    *    Given: color-x = color-X / (color-X + color-Y + color-Z)
+    *    Hence: (color-x - 1)*color-X + color.x*color-Y + color.x*color-Z = 0
+    *
+    * This is 9 simultaneous equations in the 9 variables "color-C" and can be
+    * solved by Cramer's rule.  Cramer's rule requires calculating 10 9x9 matrix
+    * determinants, however this is not as bad as it seems because only 28 of
+    * the total of 90 terms in the various matrices are non-zero.  Nevertheless
+    * Cramer's rule is notoriously numerically unstable because the determinant
+    * calculation involves the difference of large, but similar, numbers.  It is
+    * difficult to be sure that the calculation is stable for real world values
+    * and it is certain that it becomes unstable where the end points are close
+    * together.
+    *
+    * So this code uses the perhaps slighly less optimal but more understandable
+    * and totally obvious approach of calculating color-scale.
+    *
+    * This algorithm depends on the precision in white-scale and that is
+    * (1/white-y), so we can immediately see that as white-y approaches 0 the
+    * accuracy inherent in the cHRM chunk drops off substantially.
+    *
+    * libpng arithmetic: a simple invertion of the above equations
+    * ------------------------------------------------------------
+    *
+    *    white_scale = 1/white-y
+    *    white-X = white-x * white-scale
+    *    white-Y = 1.0
+    *    white-Z = (1 - white-x - white-y) * white_scale
+    *
+    *    white-C = red-C + green-C + blue-C
+    *            = red-c*red-scale + green-c*green-scale + blue-c*blue-scale
+    *
+    * This gives us three equations in (red-scale,green-scale,blue-scale) where
+    * all the coefficients are now known:
+    *
+    *    red-x*red-scale + green-x*green-scale + blue-x*blue-scale
+    *       = white-x/white-y
+    *    red-y*red-scale + green-y*green-scale + blue-y*blue-scale = 1
+    *    red-z*red-scale + green-z*green-scale + blue-z*blue-scale
+    *       = (1 - white-x - white-y)/white-y
+    *
+    * In the last equation color-z is (1 - color-x - color-y) so we can add all
+    * three equations together to get an alternative third:
+    *
+    *    red-scale + green-scale + blue-scale = 1/white-y = white-scale
+    *
+    * So now we have a Cramer's rule solution where the determinants are just
+    * 3x3 - far more tractible.  Unfortunately 3x3 determinants still involve
+    * multiplication of three coefficients so we can't guarantee to avoid
+    * overflow in the libpng fixed point representation.  Using Cramer's rule in
+    * floating point is probably a good choice here, but it's not an option for
+    * fixed point.  Instead proceed to simplify the first two equations by
+    * eliminating what is likely to be the largest value, blue-scale:
+    *
+    *    blue-scale = white-scale - red-scale - green-scale
+    *
+    * Hence:
+    *
+    *    (red-x - blue-x)*red-scale + (green-x - blue-x)*green-scale =
+    *                (white-x - blue-x)*white-scale
+    *
+    *    (red-y - blue-y)*red-scale + (green-y - blue-y)*green-scale =
+    *                1 - blue-y*white-scale
+    *
+    * And now we can trivially solve for (red-scale,green-scale):
+    *
+    *    green-scale =
+    *                (white-x - blue-x)*white-scale - (red-x - blue-x)*red-scale
+    *                -----------------------------------------------------------
+    *                                  green-x - blue-x
+    *
+    *    red-scale =
+    *                1 - blue-y*white-scale - (green-y - blue-y) * green-scale
+    *                ---------------------------------------------------------
+    *                                  red-y - blue-y
+    *
+    * Hence:
+    *
+    *    red-scale =
+    *          ( (green-x - blue-x) * (white-y - blue-y) -
+    *            (green-y - blue-y) * (white-x - blue-x) ) / white-y
+    * -------------------------------------------------------------------------
+    *  (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)
+    *
+    *    green-scale =
+    *          ( (red-y - blue-y) * (white-x - blue-x) -
+    *            (red-x - blue-x) * (white-y - blue-y) ) / white-y
+    * -------------------------------------------------------------------------
+    *  (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)
+    *
+    * Accuracy:
+    * The input values have 5 decimal digits of accuracy.  The values are all in
+    * the range 0 < value < 1, so simple products are in the same range but may
+    * need up to 10 decimal digits to preserve the original precision and avoid
+    * underflow.  Because we are using a 32-bit signed representation we cannot
+    * match this; the best is a little over 9 decimal digits, less than 10.
+    *
+    * The approach used here is to preserve the maximum precision within the
+    * signed representation.  Because the red-scale calculation above uses the
+    * difference between two products of values that must be in the range -1..+1
+    * it is sufficient to divide the product by 7; ceil(100,000/32767*2).  The
+    * factor is irrelevant in the calculation because it is applied to both
+    * numerator and denominator.
+    *
+    * Note that the values of the differences of the products of the
+    * chromaticities in the above equations tend to be small, for example for
+    * the sRGB chromaticities they are:
+    *
+    * red numerator:    -0.04751
+    * green numerator:  -0.08788
+    * denominator:      -0.2241 (without white-y multiplication)
+    *
+    *  The resultant Y coefficients from the chromaticities of some widely used
+    *  color space definitions are (to 15 decimal places):
+    *
+    *  sRGB
+    *    0.212639005871510 0.715168678767756 0.072192315360734
+    *  Kodak ProPhoto
+    *    0.288071128229293 0.711843217810102 0.000085653960605
+    *  Adobe RGB
+    *    0.297344975250536 0.627363566255466 0.075291458493998
+    *  Adobe Wide Gamut RGB
+    *    0.258728243040113 0.724682314948566 0.016589442011321
+    */
+   /* By the argument, above overflow should be impossible here. The return
+    * value of 2 indicates an internal error to the caller.
+    */
+   if (!png_muldiv(&left, xy.greenx-xy.bluex, xy.redy - xy.bluey, 7)) return 2;
+   if (!png_muldiv(&right, xy.greeny-xy.bluey, xy.redx - xy.bluex, 7)) return 2;
+   denominator = left - right;
+
+   /* Now find the red numerator. */
+   if (!png_muldiv(&left, xy.greenx-xy.bluex, xy.whitey-xy.bluey, 7)) return 2;
+   if (!png_muldiv(&right, xy.greeny-xy.bluey, xy.whitex-xy.bluex, 7)) return 2;
+
+   /* Overflow is possible here and it indicates an extreme set of PNG cHRM
+    * chunk values.  This calculation actually returns the reciprocal of the
+    * scale value because this allows us to delay the multiplication of white-y
+    * into the denominator, which tends to produce a small number.
+    */
+   if (!png_muldiv(&red_inverse, xy.whitey, denominator, left-right) ||
+       red_inverse <= xy.whitey /* r+g+b scales = white scale */)
+      return 1;
+
+   /* Similarly for green_inverse: */
+   if (!png_muldiv(&left, xy.redy-xy.bluey, xy.whitex-xy.bluex, 7)) return 2;
+   if (!png_muldiv(&right, xy.redx-xy.bluex, xy.whitey-xy.bluey, 7)) return 2;
+   if (!png_muldiv(&green_inverse, xy.whitey, denominator, left-right) ||
+       green_inverse <= xy.whitey)
+      return 1;
+
+   /* And the blue scale, the checks above guarantee this can't overflow but it
+    * can still produce 0 for extreme cHRM values.
+    */
+   blue_scale = png_reciprocal(xy.whitey) - png_reciprocal(red_inverse) -
+      png_reciprocal(green_inverse);
+   if (blue_scale <= 0) return 1;
+
+
+   /* And fill in the png_XYZ: */
+   if (!png_muldiv(&XYZ->redX, xy.redx, PNG_FP_1, red_inverse)) return 1;
+   if (!png_muldiv(&XYZ->redY, xy.redy, PNG_FP_1, red_inverse)) return 1;
+   if (!png_muldiv(&XYZ->redZ, PNG_FP_1 - xy.redx - xy.redy, PNG_FP_1,
+      red_inverse))
+      return 1;
+
+   if (!png_muldiv(&XYZ->greenX, xy.greenx, PNG_FP_1, green_inverse)) return 1;
+   if (!png_muldiv(&XYZ->greenY, xy.greeny, PNG_FP_1, green_inverse)) return 1;
+   if (!png_muldiv(&XYZ->greenZ, PNG_FP_1 - xy.greenx - xy.greeny, PNG_FP_1,
+      green_inverse))
+      return 1;
+
+   if (!png_muldiv(&XYZ->blueX, xy.bluex, blue_scale, PNG_FP_1)) return 1;
+   if (!png_muldiv(&XYZ->blueY, xy.bluey, blue_scale, PNG_FP_1)) return 1;
+   if (!png_muldiv(&XYZ->blueZ, PNG_FP_1 - xy.bluex - xy.bluey, blue_scale,
+      PNG_FP_1))
+      return 1;
+
+   return 0; /*success*/
+}
+
+int png_XYZ_from_xy_checked(png_structp png_ptr, png_XYZ *XYZ, png_xy xy)
+{
+   switch (png_XYZ_from_xy(XYZ, xy))
+   {
+      case 0: /* success */
+         return 1;
+
+      case 1:
+         /* The chunk may be technically valid, but we got png_fixed_point
+          * overflow while trying to get XYZ values out of it.  This is
+          * entirely benign - the cHRM chunk is pretty extreme.
+          */
+         png_chunk_benign_error(png_ptr,
+            "extreme cHRM chunk cannot be converted to tristimulus values");
+         break;
+
+      default:
+         /* libpng is broken; this should be a warning but if it happens we
+          * want error reports so for the moment it is an error.
+          */
+         png_error(png_ptr, "internal error in png_XYZ_from_xy");
+         break;
+   }
+
+   /* ERROR RETURN */
+   return 0;
+}
+#endif
+
 void /* PRIVATE */
 png_check_IHDR(png_structp png_ptr,
    png_uint_32 width, png_uint_32 height, int bit_depth,
@@ -946,16 +1257,9 @@ png_check_IHDR(png_structp png_ptr,
 /* Check an ASCII formated floating point value, see the more detailed
  * comments in pngpriv.h
  */
-/* The following is used internally to preserve the 'valid' flag */
+/* The following is used internally to preserve the sticky flags */
 #define png_fp_add(state, flags) ((state) |= (flags))
-#define png_fp_set(state, value)\
-   ((state) = (value) | ((state) & PNG_FP_WAS_VALID))
-
-/* Internal type codes: bits above the base state! */
-#define PNG_FP_SIGN   0  /* [+-] */
-#define PNG_FP_DOT    4  /* . */
-#define PNG_FP_DIGIT  8  /* [0123456789] */
-#define PNG_FP_E     12  /* [Ee] */
+#define png_fp_set(state, value) ((state) = (value) | ((state) & PNG_FP_STICKY))
 
 int /* PRIVATE */
 png_check_fp_number(png_const_charp string, png_size_t size, int *statep,
@@ -968,55 +1272,55 @@ png_check_fp_number(png_const_charp string, png_size_t size, int *statep,
    {
       int type;
       /* First find the type of the next character */
+      switch (string[i])
       {
-         char ch = string[i];
-
-         if (ch >= 48 && ch <= 57)
-            type = PNG_FP_DIGIT;
-
-         else switch (ch)
-         {
-         case 43: case 45:  type = PNG_FP_SIGN;  break;
-         case 46:           type = PNG_FP_DOT;   break;
-         case 69: case 101: type = PNG_FP_E;     break;
-         default:           goto PNG_FP_End;
-         }
+      case 43:  type = PNG_FP_SAW_SIGN;                   break;
+      case 45:  type = PNG_FP_SAW_SIGN + PNG_FP_NEGATIVE; break;
+      case 46:  type = PNG_FP_SAW_DOT;                    break;
+      case 48:  type = PNG_FP_SAW_DIGIT;                  break;
+      case 49: case 50: case 51: case 52:
+      case 53: case 54: case 55: case 56:
+      case 57:  type = PNG_FP_SAW_DIGIT + PNG_FP_NONZERO; break;
+      case 69:
+      case 101: type = PNG_FP_SAW_E;                      break;
+      default:  goto PNG_FP_End;
       }
 
       /* Now deal with this type according to the current
        * state, the type is arranged to not overlap the
        * bits of the PNG_FP_STATE.
        */
-      switch ((state & PNG_FP_STATE) + type)
+      switch ((state & PNG_FP_STATE) + (type & PNG_FP_SAW_ANY))
       {
-      case PNG_FP_INTEGER + PNG_FP_SIGN:
+      case PNG_FP_INTEGER + PNG_FP_SAW_SIGN:
          if (state & PNG_FP_SAW_ANY)
             goto PNG_FP_End; /* not a part of the number */
 
-         png_fp_add(state, PNG_FP_SAW_SIGN);
+         png_fp_add(state, type);
          break;
 
-      case PNG_FP_INTEGER + PNG_FP_DOT:
+      case PNG_FP_INTEGER + PNG_FP_SAW_DOT:
          /* Ok as trailer, ok as lead of fraction. */
          if (state & PNG_FP_SAW_DOT) /* two dots */
             goto PNG_FP_End;
 
          else if (state & PNG_FP_SAW_DIGIT) /* trailing dot? */
-            png_fp_add(state, PNG_FP_SAW_DOT);
+            png_fp_add(state, type);
 
          else
-            png_fp_set(state, PNG_FP_FRACTION | PNG_FP_SAW_DOT);
+            png_fp_set(state, PNG_FP_FRACTION | type);
 
          break;
 
-      case PNG_FP_INTEGER + PNG_FP_DIGIT:
+      case PNG_FP_INTEGER + PNG_FP_SAW_DIGIT:
          if (state & PNG_FP_SAW_DOT) /* delayed fraction */
             png_fp_set(state, PNG_FP_FRACTION | PNG_FP_SAW_DOT);
 
-         png_fp_add(state, PNG_FP_SAW_DIGIT + PNG_FP_WAS_VALID);
+         png_fp_add(state, type | PNG_FP_WAS_VALID);
 
          break;
-      case PNG_FP_INTEGER + PNG_FP_E:
+
+      case PNG_FP_INTEGER + PNG_FP_SAW_E:
          if ((state & PNG_FP_SAW_DIGIT) == 0)
             goto PNG_FP_End;
 
@@ -1024,17 +1328,17 @@ png_check_fp_number(png_const_charp string, png_size_t size, int *statep,
 
          break;
 
-   /* case PNG_FP_FRACTION + PNG_FP_SIGN:
-         goto PNG_FP_End; ** no sign in exponent */
+   /* case PNG_FP_FRACTION + PNG_FP_SAW_SIGN:
+         goto PNG_FP_End; ** no sign in fraction */
 
-   /* case PNG_FP_FRACTION + PNG_FP_DOT:
+   /* case PNG_FP_FRACTION + PNG_FP_SAW_DOT:
          goto PNG_FP_End; ** Because SAW_DOT is always set */
 
-      case PNG_FP_FRACTION + PNG_FP_DIGIT:
-         png_fp_add(state, PNG_FP_SAW_DIGIT + PNG_FP_WAS_VALID);
+      case PNG_FP_FRACTION + PNG_FP_SAW_DIGIT:
+         png_fp_add(state, type | PNG_FP_WAS_VALID);
          break;
 
-      case PNG_FP_FRACTION + PNG_FP_E:
+      case PNG_FP_FRACTION + PNG_FP_SAW_E:
          /* This is correct because the trailing '.' on an
           * integer is handled above - so we can only get here
           * with the sequence ".E" (with no preceding digits).
@@ -1046,7 +1350,7 @@ png_check_fp_number(png_const_charp string, png_size_t size, int *statep,
 
          break;
 
-      case PNG_FP_EXPONENT + PNG_FP_SIGN:
+      case PNG_FP_EXPONENT + PNG_FP_SAW_SIGN:
          if (state & PNG_FP_SAW_ANY)
             goto PNG_FP_End; /* not a part of the number */
 
@@ -1054,15 +1358,15 @@ png_check_fp_number(png_const_charp string, png_size_t size, int *statep,
 
          break;
 
-   /* case PNG_FP_EXPONENT + PNG_FP_DOT:
+   /* case PNG_FP_EXPONENT + PNG_FP_SAW_DOT:
          goto PNG_FP_End; */
 
-      case PNG_FP_EXPONENT + PNG_FP_DIGIT:
-         png_fp_add(state, PNG_FP_SAW_DIGIT + PNG_FP_WAS_VALID);
+      case PNG_FP_EXPONENT + PNG_FP_SAW_DIGIT:
+         png_fp_add(state, PNG_FP_SAW_DIGIT | PNG_FP_WAS_VALID);
 
          break;
 
-   /* case PNG_FP_EXPONEXT + PNG_FP_E:
+   /* case PNG_FP_EXPONEXT + PNG_FP_SAW_E:
          goto PNG_FP_End; */
 
       default: goto PNG_FP_End; /* I.e. break 2 */
@@ -1090,8 +1394,11 @@ png_check_fp_string(png_const_charp string, png_size_t size)
    int        state=0;
    png_size_t char_index=0;
 
-   return png_check_fp_number(string, size, &state, &char_index) &&
-      (char_index == size || string[char_index] == 0);
+   if (png_check_fp_number(string, size, &state, &char_index) &&
+      (char_index == size || string[char_index] == 0))
+      return state /* must be non-zero - see above */;
+
+   return 0; /* i.e. fail */
 }
 #endif /* pCAL or sCAL */
 
@@ -1845,7 +2152,7 @@ png_8bit_l2[128] =
 #endif
 };
 
-static png_int_32
+PNG_STATIC png_int_32
 png_log8bit(unsigned int x)
 {
    unsigned int lg2 = 0;
@@ -1901,7 +2208,7 @@ png_log8bit(unsigned int x)
  * Zero  (257):      0
  * End   (258):  23499
  */
-static png_int_32
+PNG_STATIC png_int_32
 png_log16bit(png_uint_32 x)
 {
    unsigned int lg2 = 0;
@@ -1995,7 +2302,7 @@ for (i=11;i>=0;--i){ print i, " ", (1 - e(-(2^i)/65536*l(2))) * 2^(32-i), "\n"}
     0 45425.85339951654943850496
 #endif
 
-static png_uint_32
+PNG_STATIC png_uint_32
 png_exp(png_fixed_point x)
 {
    if (x > 0 && x <= 0xfffff) /* Else overflow or zero (underflow) */
@@ -2043,7 +2350,7 @@ png_exp(png_fixed_point x)
    return 0;
 }
 
-static png_byte
+PNG_STATIC png_byte
 png_exp8bit(png_fixed_point lg2)
 {
    /* Get a 32-bit value: */
@@ -2057,7 +2364,7 @@ png_exp8bit(png_fixed_point lg2)
    return (png_byte)((x + 0x7fffffU) >> 24);
 }
 
-static png_uint_16
+PNG_STATIC png_uint_16
 png_exp16bit(png_fixed_point lg2)
 {
    /* Get a 32-bit value: */
@@ -2369,7 +2676,7 @@ png_build_gamma_table(png_structp png_ptr, int bit_depth)
      else
         shift = 0; /* keep all 16 bits */
 
-     if (png_ptr->transformations & (PNG_16_TO_8 | PNG_CHOP_16_TO_8))
+     if (png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8))
      {
         /* PNG_MAX_GAMMA_8 is the number of bits to keep - effectively
          * the significant bits in the *input* when the output will
@@ -2385,12 +2692,12 @@ png_build_gamma_table(png_structp png_ptr, int bit_depth)
      png_ptr->gamma_shift = shift;
 
 #ifdef PNG_16BIT_SUPPORTED
-     /* NOTE: prior to 1.5.3 this test used to include PNG_BACKGROUND (now
+     /* NOTE: prior to 1.5.4 this test used to include PNG_BACKGROUND (now
       * PNG_COMPOSE).  This effectively smashed the background calculation for
       * 16-bit output because the 8-bit table assumes the result will be reduced
       * to 8 bits.
       */
-     if (png_ptr->transformations & (PNG_16_TO_8 | PNG_CHOP_16_TO_8))
+     if (png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8))
 #endif
          png_build_16to8_table(png_ptr, &png_ptr->gamma_16_table, shift,
          png_ptr->screen_gamma > 0 ? png_product2(png_ptr->gamma,

png.h

@@ -1,7 +1,7 @@
 
 /* png.h - header file for PNG reference library
  *
- * libpng version 1.5.4beta02 - June 14, 2011
+ * libpng version 1.5.5beta06 - August 25, 2011
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -11,7 +11,7 @@
  * Authors and maintainers:
  *   libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
  *   libpng versions 0.89c, June 1996, through 0.96, May 1997: Andreas Dilger
- *   libpng versions 0.97, January 1998, through 1.5.4beta02 - June 14, 2011: Glenn
+ *   libpng versions 0.97, January 1998, through 1.5.5beta06 - August 25, 2011: Glenn
  *   See also "Contributing Authors", below.
  *
  * Note about libpng version numbers:
@@ -154,7 +154,10 @@
  *    1.5.3rc01-02            15    10503  15.so.15.3[.0]
  *    1.5.3beta11             15    10503  15.so.15.3[.0]
  *    1.5.3 [omitted]
- *    1.5.4beta01-02          15    10504  15.so.15.4[.0]
+ *    1.5.4beta01-08          15    10504  15.so.15.4[.0]
+ *    1.5.4rc01               15    10504  15.so.15.4[.0]
+ *    1.5.4                   15    10504  15.so.15.4[.0]
+ *    1.5.5beta01-06          15    10505  15.so.15.5[.0]
  *
  *   Henceforth the source version will match the shared-library major
  *   and minor numbers; the shared-library major version number will be
@@ -186,7 +189,7 @@
  *
  * This code is released under the libpng license.
  *
- * libpng versions 1.2.6, August 15, 2004, through 1.5.4beta02, June 14, 2011, are
+ * libpng versions 1.2.6, August 15, 2004, through 1.5.5beta06, August 25, 2011, are
  * Copyright (c) 2004, 2006-2011 Glenn Randers-Pehrson, and are
  * distributed according to the same disclaimer and license as libpng-1.2.5
  * with the following individual added to the list of Contributing Authors:
@@ -298,13 +301,13 @@
  * Y2K compliance in libpng:
  * =========================
  *
- *    June 14, 2011
+ *    August 25, 2011
  *
  *    Since the PNG Development group is an ad-hoc body, we can't make
  *    an official declaration.
  *
  *    This is your unofficial assurance that libpng from version 0.71 and
- *    upward through 1.5.4beta02 are Y2K compliant.  It is my belief that
+ *    upward through 1.5.5beta06 are Y2K compliant.  It is my belief that
  *    earlier versions were also Y2K compliant.
  *
  *    Libpng only has two year fields.  One is a 2-byte unsigned integer
@@ -359,9 +362,9 @@
  */
 
 /* Version information for png.h - this should match the version in png.c */
-#define PNG_LIBPNG_VER_STRING "1.5.4beta02"
+#define PNG_LIBPNG_VER_STRING "1.5.5beta06"
 #define PNG_HEADER_VERSION_STRING \
-     " libpng version 1.5.4beta02 - June 14, 2011\n"
+     " libpng version 1.5.5beta06 - August 25, 2011\n"
 
 #define PNG_LIBPNG_VER_SONUM   15
 #define PNG_LIBPNG_VER_DLLNUM  15
@@ -369,12 +372,12 @@
 /* These should match the first 3 components of PNG_LIBPNG_VER_STRING: */
 #define PNG_LIBPNG_VER_MAJOR   1
 #define PNG_LIBPNG_VER_MINOR   5
-#define PNG_LIBPNG_VER_RELEASE 4
+#define PNG_LIBPNG_VER_RELEASE 5
 /* This should match the numeric part of the final component of
  * PNG_LIBPNG_VER_STRING, omitting any leading zero:
  */
 
-#define PNG_LIBPNG_VER_BUILD  02
+#define PNG_LIBPNG_VER_BUILD  06
 
 /* Release Status */
 #define PNG_LIBPNG_BUILD_ALPHA    1
@@ -399,7 +402,7 @@
  * version 1.0.0 was mis-numbered 100 instead of 10000).  From
  * version 1.0.1 it's    xxyyzz, where x=major, y=minor, z=release
  */
-#define PNG_LIBPNG_VER 10504 /* 1.5.4 */
+#define PNG_LIBPNG_VER 10505 /* 1.5.5 */
 
 /* Library configuration: these options cannot be changed after
  * the library has been built.
@@ -521,7 +524,7 @@ extern "C" {
 /* This triggers a compiler error in png.c, if png.c and png.h
  * do not agree upon the version number.
  */
-typedef char* png_libpng_version_1_5_4beta02;
+typedef char* png_libpng_version_1_5_5beta06;
 
 /* Three color definitions.  The order of the red, green, and blue, (and the
  * exact size) is not important, although the size of the fields need to
@@ -598,7 +601,7 @@ typedef png_sPLT_t FAR * FAR * png_sPLT_tpp;
  * and whether that contents is compressed or not.  The "key" field
  * points to a regular zero-terminated C string.  The "text", "lang", and
  * "lang_key" fields can be regular C strings, empty strings, or NULL pointers.
- * However, the * structure returned by png_get_text() will always contain
+ * However, the structure returned by png_get_text() will always contain
  * regular zero-terminated C strings (possibly empty), never NULL pointers,
  * so they can be safely used in printf() and other string-handling functions.
  */
@@ -900,8 +903,9 @@ PNG_FUNCTION(void, (PNGCAPI *png_longjmp_ptr), PNGARG((jmp_buf, int)), typedef);
 #define PNG_TRANSFORM_STRIP_FILLER_AFTER 0x1000 /* write only */
 /* Added to libpng-1.4.0 */
 #define PNG_TRANSFORM_GRAY_TO_RGB   0x2000      /* read only */
-/* Added to libpng-1.5.3 */
+/* Added to libpng-1.5.4 */
 #define PNG_TRANSFORM_EXPAND_16     0x4000      /* read only */
+#define PNG_TRANSFORM_SCALE_16      0x8000      /* read only */
 
 /* Flags for MNG supported features */
 #define PNG_FLAG_MNG_EMPTY_PLTE     0x01
@@ -1404,7 +1408,7 @@ PNG_EXPORT(46, void, png_set_invert_mono, (png_structp png_ptr));
 
 #ifdef PNG_READ_BACKGROUND_SUPPORTED
 /* Handle alpha and tRNS by replacing with a background color.  Prior to
- * libpng-1.5.3 this API must not be called before the PNG file header has been
+ * libpng-1.5.4 this API must not be called before the PNG file header has been
  * read.  Doing so will result in unexpected behavior and possible warnings or
  * errors if the PNG file contains a bKGD chunk.
  */
@@ -1422,15 +1426,15 @@ PNG_FIXED_EXPORT(215, void, png_set_background_fixed, (png_structp png_ptr,
 #  define PNG_BACKGROUND_GAMMA_UNIQUE  3
 #endif
 
-#ifdef PNG_READ_16_TO_8_SUPPORTED
-/* The following is always done from 1.5.4: */
-#define PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
 /* Scale a 16-bit depth file down to 8-bit, accurately. */
-PNG_EXPORT(48, void, png_set_strip_16, (png_structp png_ptr));
-#  ifdef PNG_READ_CHOP_16_TO_8_SUPPORTED
+PNG_EXPORT(229, void, png_set_scale_16, (png_structp png_ptr));
+#endif
+
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+#define PNG_READ_16_TO_8 SUPPORTED /* Name prior to 1.5.4 */
 /* Strip the second byte of information from a 16-bit depth file. */
-PNG_EXPORT(229, void, png_set_chop_16, (png_structp png_ptr));
-#  endif
+PNG_EXPORT(48, void, png_set_strip_16, (png_structp png_ptr));
 #endif
 
 #ifdef PNG_READ_QUANTIZE_SUPPORTED
@@ -2044,6 +2048,10 @@ PNG_FP_EXPORT(133, png_uint_32, png_get_cHRM, (png_const_structp png_ptr,
    png_const_infop info_ptr, double *white_x, double *white_y, double *red_x,
     double *red_y, double *green_x, double *green_y, double *blue_x,
     double *blue_y));
+PNG_FP_EXPORT(230, png_uint_32, png_get_cHRM_XYZ, (png_structp png_ptr,
+    png_const_infop info_ptr, double *red_X, double *red_Y, double *red_Z,
+    double *green_X, double *green_Y, double *green_Z, double *blue_X,
+    double *blue_Y, double *blue_Z));
 #ifdef PNG_FIXED_POINT_SUPPORTED /* Otherwise not implemented */
 PNG_FIXED_EXPORT(134, png_uint_32, png_get_cHRM_fixed,
     (png_const_structp png_ptr,
@@ -2053,6 +2061,13 @@ PNG_FIXED_EXPORT(134, png_uint_32, png_get_cHRM_fixed,
     png_fixed_point *int_green_y, png_fixed_point *int_blue_x,
     png_fixed_point *int_blue_y));
 #endif
+PNG_FIXED_EXPORT(231, png_uint_32, png_get_cHRM_XYZ_fixed,
+    (png_structp png_ptr, png_const_infop info_ptr,
+    png_fixed_point *int_red_X, png_fixed_point *int_red_Y,
+    png_fixed_point *int_red_Z, png_fixed_point *int_green_X,
+    png_fixed_point *int_green_Y, png_fixed_point *int_green_Z,
+    png_fixed_point *int_blue_X, png_fixed_point *int_blue_Y,
+    png_fixed_point *int_blue_Z));
 #endif
 
 #ifdef PNG_cHRM_SUPPORTED
@@ -2060,12 +2075,22 @@ PNG_FP_EXPORT(135, void, png_set_cHRM,
     (png_structp png_ptr, png_infop info_ptr,
     double white_x, double white_y, double red_x, double red_y, double green_x,
     double green_y, double blue_x, double blue_y));
+PNG_FP_EXPORT(232, void, png_set_cHRM_XYZ, (png_structp png_ptr,
+    png_infop info_ptr, double red_X, double red_Y, double red_Z,
+    double green_X, double green_Y, double green_Z, double blue_X,
+    double blue_Y, double blue_Z));
 PNG_FIXED_EXPORT(136, void, png_set_cHRM_fixed, (png_structp png_ptr,
     png_infop info_ptr, png_fixed_point int_white_x,
     png_fixed_point int_white_y, png_fixed_point int_red_x,
     png_fixed_point int_red_y, png_fixed_point int_green_x,
     png_fixed_point int_green_y, png_fixed_point int_blue_x,
     png_fixed_point int_blue_y));
+PNG_FIXED_EXPORT(233, void, png_set_cHRM_XYZ_fixed, (png_structp png_ptr,
+    png_infop info_ptr, png_fixed_point int_red_X, png_fixed_point int_red_Y,
+    png_fixed_point int_red_Z, png_fixed_point int_green_X,
+    png_fixed_point int_green_Y, png_fixed_point int_green_Z,
+    png_fixed_point int_blue_X, png_fixed_point int_blue_Y,
+    png_fixed_point int_blue_Z));
 #endif
 
 #ifdef PNG_gAMA_SUPPORTED
@@ -2279,7 +2304,7 @@ PNG_EXPORT(171, void, png_set_sCAL_s,
    handling or default unknown chunk handling is not desired.  Any chunks not
    listed will be handled in the default manner.  The IHDR and IEND chunks
    must not be listed.
-      keep = 0: follow default behaviour
+      keep = 0: follow default behavior
            = 1: do not keep
            = 2: keep only if safe-to-copy
            = 3: keep even if unsafe-to-copy
@@ -2573,7 +2598,7 @@ PNG_EXPORT(207, void, png_save_uint_16, (png_bytep buf, unsigned int i));
  * scripts/symbols.def as well.
  */
 #ifdef PNG_EXPORT_LAST_ORDINAL
-  PNG_EXPORT_LAST_ORDINAL(229);
+  PNG_EXPORT_LAST_ORDINAL(233);
 #endif
 
 #ifdef __cplusplus

pngconf.h

@@ -1,7 +1,7 @@
 
 /* pngconf.h - machine configurable file for libpng
  *
- * libpng version 1.5.4beta02 - June 14, 2011
+ * libpng version 1.5.5beta06 - August 25, 2011
  *
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
@@ -164,7 +164,9 @@
  *                       'type', compiler specific.
  *
  * PNG_DLL_EXPORT Set to the magic to use during a libpng build to
- *                make a symbol exported from the DLL.
+ *                make a symbol exported from the DLL.  Not used in the
+ *                public header files; see pngpriv.h for how it is used
+ *                in the libpng build.
  *
  * PNG_DLL_IMPORT Set to the magic to force the libpng symbols to come
  *                from a DLL - used to define PNG_IMPEXP when
@@ -258,25 +260,14 @@
 #  define PNGAPI PNGCAPI
 #endif
 
-/* The default for PNG_IMPEXP depends on whether the library is
- * being built or used.
+/* PNG_IMPEXP may be set on the compilation system command line or (if not set)
+ * then in an internal header file when building the library, otherwise (when
+ * using the library) it is set here.
  */
 #ifndef PNG_IMPEXP
-#  ifdef PNGLIB_BUILD
-    /* Building the library */
-#    if (defined(DLL_EXPORT)/*from libtool*/ ||\
-        defined(_WINDLL) || defined(_DLL) || defined(__DLL__) ||\
-        defined(_USRDLL) ||\
-        defined(PNG_BUILD_DLL)) && defined(PNG_DLL_EXPORT)
-      /* Building a DLL. */
-#      define PNG_IMPEXP PNG_DLL_EXPORT
-#    endif /* DLL */
-#  else
-    /* Using the library */
-#    if defined(PNG_USE_DLL) && defined(PNG_DLL_IMPORT)
-      /* This forces use of a DLL, disallowing static linking */
-#      define PNG_IMPEXP PNG_DLL_IMPORT
-#    endif
+#  if defined(PNG_USE_DLL) && defined(PNG_DLL_IMPORT)
+     /* This forces use of a DLL, disallowing static linking */
+#    define PNG_IMPEXP PNG_DLL_IMPORT
 #  endif
 
 #  ifndef PNG_IMPEXP
@@ -356,25 +347,18 @@
 #    ifndef PNG_ALLOCATED
 #      define PNG_ALLOCATED  __attribute__((__malloc__))
 #    endif
-
-    /* This specifically protects structure members that should only be
-     * accessed from within the library, therefore should be empty during
-     * a library build.
-     */
-#    ifndef PNGLIB_BUILD
-#      ifndef PNG_DEPRECATED
-#        define PNG_DEPRECATED __attribute__((__deprecated__))
+#    ifndef PNG_DEPRECATED
+#      define PNG_DEPRECATED __attribute__((__deprecated__))
+#    endif
+#    ifndef PNG_PRIVATE
+#      if 0 /* Doesn't work so we use deprecated instead*/
+#        define PNG_PRIVATE \
+          __attribute__((warning("This function is not exported by libpng.")))
+#      else
+#        define PNG_PRIVATE \
+          __attribute__((__deprecated__))
 #      endif
-#      ifndef PNG_PRIVATE
-#        if 0 /* Doesn't work so we use deprecated instead*/
-#          define PNG_PRIVATE \
-            __attribute__((warning("This function is not exported by libpng.")))
-#        else
-#          define PNG_PRIVATE \
-            __attribute__((__deprecated__))
-#        endif
-#      endif
-#    endif /* PNGLIB_BUILD */
+#    endif
 #  endif /* __GNUC__ */
 
 #  if defined(_MSC_VER)  && (_MSC_VER >= 1300)
@@ -385,21 +369,16 @@
 #      define PNG_NORETURN   __declspec(noreturn)
 #    endif
 #    ifndef PNG_ALLOCATED
-#      define PNG_ALLOCATED __declspec(restrict)
+#      if defined(_MSC_VER)  && (_MSC_VER >= 1300)
+#        define PNG_ALLOCATED __declspec(restrict)
+#      endif
+#    endif
+#    ifndef PNG_DEPRECATED
+#      define PNG_DEPRECATED __declspec(deprecated)
+#    endif
+#    ifndef PNG_PRIVATE
+#      define PNG_PRIVATE __declspec(deprecated)
 #    endif
-
-    /* This specifically protects structure members that should only be
-     * accessed from within the library, therefore should be empty during
-     * a library build.
-     */
-#    ifndef PNGLIB_BUILD
-#      ifndef PNG_DEPRECATED
-#        define PNG_DEPRECATED __declspec(deprecated)
-#      endif
-#      ifndef PNG_PRIVATE
-#        define PNG_PRIVATE __declspec(deprecated)
-#      endif
-#    endif /* PNGLIB_BUILD */
 #  endif /* _MSC_VER */
 #endif /* PNG_PEDANTIC_WARNINGS */
 

pngerror.c

@@ -1,7 +1,7 @@
 
 /* pngerror.c - stub functions for i/o and memory allocation
  *
- * Last changed in libpng 1.5.4 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.4 [July 7, 2011]
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -507,7 +507,7 @@ png_default_error,(png_structp png_ptr, png_const_charp error_message),
 {
 #ifdef PNG_CONSOLE_IO_SUPPORTED
 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
-   /* Check on NULL only added in 1.5.3 */
+   /* Check on NULL only added in 1.5.4 */
    if (error_message != NULL && *error_message == PNG_LITERAL_SHARP)
    {
       /* Strip "#nnnn " from beginning of error message. */

pngget.c

@@ -459,6 +459,65 @@ png_get_bKGD(png_const_structp png_ptr, png_infop info_ptr,
 #endif
 
 #ifdef PNG_cHRM_SUPPORTED
+/* The XYZ APIs were added in 1.5.5 to take advantage of the code added at the
+ * same time to correct the rgb grayscale coefficient defaults obtained from the
+ * cHRM chunk in 1.5.4
+ */
+png_uint_32 PNGFAPI
+png_get_cHRM_XYZ_fixed(png_structp png_ptr, png_const_infop info_ptr,
+    png_fixed_point *int_red_X, png_fixed_point *int_red_Y,
+    png_fixed_point *int_red_Z, png_fixed_point *int_green_X,
+    png_fixed_point *int_green_Y, png_fixed_point *int_green_Z,
+    png_fixed_point *int_blue_X, png_fixed_point *int_blue_Y,
+    png_fixed_point *int_blue_Z)
+{
+   if (png_ptr != NULL && info_ptr != NULL && (info_ptr->valid & PNG_INFO_cHRM))
+   {
+      png_xy xy;
+      png_XYZ XYZ;
+
+      png_debug1(1, "in %s retrieval function", "cHRM_XYZ");
+
+      xy.whitex = info_ptr->x_white;
+      xy.whitey = info_ptr->y_white;
+      xy.redx = info_ptr->x_red;
+      xy.redy = info_ptr->y_red;
+      xy.greenx = info_ptr->x_green;
+      xy.greeny = info_ptr->y_green;
+      xy.bluex = info_ptr->x_blue;
+      xy.bluey = info_ptr->y_blue;
+
+      /* The *_checked function handles error reporting, so just return 0 if
+       * there is a failure here.
+       */
+      if (png_XYZ_from_xy_checked(png_ptr, &XYZ, xy))
+      {
+         if (int_red_X != NULL)
+            *int_red_X = XYZ.redX;
+         if (int_red_Y != NULL)
+            *int_red_Y = XYZ.redY;
+         if (int_red_Z != NULL)
+            *int_red_Z = XYZ.redZ;
+         if (int_green_X != NULL)
+            *int_green_X = XYZ.greenX;
+         if (int_green_Y != NULL)
+            *int_green_Y = XYZ.greenY;
+         if (int_green_Z != NULL)
+            *int_green_Z = XYZ.greenZ;
+         if (int_blue_X != NULL)
+            *int_blue_X = XYZ.blueX;
+         if (int_blue_Y != NULL)
+            *int_blue_Y = XYZ.blueY;
+         if (int_blue_Z != NULL)
+            *int_blue_Z = XYZ.blueZ;
+
+         return (PNG_INFO_cHRM);
+      }
+   }
+
+   return (0);
+}
+
 #  ifdef PNG_FLOATING_POINT_SUPPORTED
 png_uint_32 PNGAPI
 png_get_cHRM(png_const_structp png_ptr, png_const_infop info_ptr,
@@ -490,6 +549,42 @@ png_get_cHRM(png_const_structp png_ptr, png_const_infop info_ptr,
 
    return (0);
 }
+
+png_uint_32 PNGAPI
+png_get_cHRM_XYZ(png_structp png_ptr, png_const_infop info_ptr,
+   double *red_X, double *red_Y, double *red_Z, double *green_X,
+   double *green_Y, double *green_Z, double *blue_X, double *blue_Y,
+   double *blue_Z)
+{
+   png_XYZ XYZ;
+
+   if (png_get_cHRM_XYZ_fixed(png_ptr, info_ptr,
+      &XYZ.redX, &XYZ.redY, &XYZ.redZ, &XYZ.greenX, &XYZ.greenY, &XYZ.greenZ,
+      &XYZ.blueX, &XYZ.blueY, &XYZ.blueZ) & PNG_INFO_cHRM)
+   {
+      if (red_X != NULL)
+         *red_X = png_float(png_ptr, XYZ.redX, "cHRM red X");
+      if (red_Y != NULL)
+         *red_Y = png_float(png_ptr, XYZ.redY, "cHRM red Y");
+      if (red_Z != NULL)
+         *red_Z = png_float(png_ptr, XYZ.redZ, "cHRM red Z");
+      if (green_X != NULL)
+         *green_X = png_float(png_ptr, XYZ.greenX, "cHRM green X");
+      if (green_Y != NULL)
+         *green_Y = png_float(png_ptr, XYZ.greenY, "cHRM green Y");
+      if (green_Z != NULL)
+         *green_Z = png_float(png_ptr, XYZ.greenZ, "cHRM green Z");
+      if (blue_X != NULL)
+         *blue_X = png_float(png_ptr, XYZ.blueX, "cHRM blue X");
+      if (blue_Y != NULL)
+         *blue_Y = png_float(png_ptr, XYZ.blueY, "cHRM blue Y");
+      if (blue_Z != NULL)
+         *blue_Z = png_float(png_ptr, XYZ.blueZ, "cHRM blue Z");
+      return (PNG_INFO_cHRM);
+   }
+
+   return (0);
+}
 #  endif
 
 #  ifdef PNG_FIXED_POINT_SUPPORTED

pnginfo.h

@@ -138,7 +138,6 @@ defined(PNG_READ_BACKGROUND_SUPPORTED)
     * single color specified that should be treated as fully transparent.
     * Data is valid if (valid & PNG_INFO_tRNS) is non-zero.
     */
-   png_bytep trans;    /* alpha values for paletted image */
    png_bytep trans_alpha;    /* alpha values for paletted image */
    png_color_16 trans_color; /* transparent color for non-palette image */
 #endif

pngmem.c

@@ -1,7 +1,7 @@
 
 /* pngmem.c - stub functions for memory allocation
  *
- * Last changed in libpng 1.5.4 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.4 [July 7, 2011]
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)

pngpriv.h

@@ -6,7 +6,7 @@
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
- * Last changed in libpng 1.5.4 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.5 [(PENDING RELEASE)]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -44,7 +44,8 @@
  */
 #include <stdlib.h>
 
-#define PNGLIB_BUILD
+#define PNGLIB_BUILD /*libpng is being built, not used*/
+
 #ifdef PNG_USER_CONFIG
 #  include "pngusr.h"
    /* These should have been defined in pngusr.h */
@@ -55,10 +56,80 @@
 #    define PNG_USER_DLLFNAME_POSTFIX "Cb"
 #  endif
 #endif
+
+/* Is this a build of a DLL where compilation of the object modules requires
+ * different preprocessor settings to those required for a simple library?  If
+ * so PNG_BUILD_DLL must be set.
+ *
+ * If libpng is used inside a DLL but that DLL does not export the libpng APIs
+ * PNG_BUILD_DLL must not be set.  To avoid the code below kicking in build a
+ * static library of libpng then link the DLL against that.
+ */
+#ifndef PNG_BUILD_DLL
+#  ifdef DLL_EXPORT
+      /* This is set by libtool when files are compiled for a DLL; libtool
+       * always compiles twice, even on systems where it isn't necessary.  Set
+       * PNG_BUILD_DLL in case it is necessary:
+       */
+#     define PNG_BUILD_DLL
+#  else
+#     ifdef _WINDLL
+         /* This is set by the Microsoft Visual Studio IDE in projects that
+          * build a DLL.  It can't easily be removed from those projects (it
+          * isn't visible in the Visual Studio UI) so it is a fairly reliable
+          * indication that PNG_IMPEXP needs to be set to the DLL export
+          * attributes.
+          */
+#        define PNG_BUILD_DLL
+#     else
+#        ifdef __DLL__
+            /* This is set by the Borland C system when compiling for a DLL
+             * (as above.)
+             */
+#           define PNG_BUILD_DLL
+#        else
+            /* Add additional compiler cases here. */
+#        endif
+#     endif
+#  endif
+#endif /* Setting PNG_BUILD_DLL if required */
+
+/* See pngconf.h for more details: the builder of the library may set this on
+ * the command line to the right thing for the specific compilation system or it
+ * may be automagically set above (at present we know of no system where it does
+ * need to be set on the command line.)
+ *
+ * PNG_IMPEXP must be set here when building the library to prevent pngconf.h
+ * setting it to the "import" setting for a DLL build.
+ */
+#ifndef PNG_IMPEXP
+#  ifdef PNG_BUILD_DLL
+#     define PNG_IMPEXP PNG_DLL_EXPORT
+#  else
+      /* Not building a DLL, or the DLL doesn't require specific export
+       * definitions.
+       */
+#     define PNG_IMPEXP
+#  endif
+#endif
+
+/* No warnings for private or deprecated functions in the build: */
+#ifndef PNG_DEPRECATED
+#  define PNG_DEPRECATED
+#endif
+#ifndef PNG_PRIVATE
+#  define PNG_PRIVATE
+#endif
+
 #include "png.h"
 #include "pnginfo.h"
 #include "pngstruct.h"
 
+/* pngconf.h does not set PNG_DLL_EXPORT unless it is required, so: */
+#ifndef PNG_DLL_EXPORT
+#  define PNG_DLL_EXPORT
+#endif
+
 /* This is used for 16 bit gamma tables - only the top level pointers are const,
  * this could be changed:
  */
@@ -115,8 +186,15 @@ typedef PNG_CONST png_uint_16p FAR * png_const_uint_16pp;
 #  define PNG_ZBUF_SIZE 65536L
 #endif
 
+/* PNG_STATIC is used to mark internal file scope functions if they need to be
+ * accessed for implementation tests (see the code in tests/?*).
+ */
+#ifndef PNG_STATIC
+#   define PNG_STATIC static
+#endif
+
 /* If warnings or errors are turned off the code is disabled or redirected here.
- * From 1.5.3 functions have been added to allow very limited formatting of
+ * From 1.5.4 functions have been added to allow very limited formatting of
  * error and warning messages - this code will also be disabled here.
  */
 #ifdef PNG_WARNINGS_SUPPORTED
@@ -281,7 +359,7 @@ typedef PNG_CONST png_uint_16p FAR * png_const_uint_16pp;
 #define PNG_COMPOSE             0x0080     /* Was PNG_BACKGROUND */
 #define PNG_BACKGROUND_EXPAND   0x0100
 #define PNG_EXPAND_16           0x0200     /* Added to libpng 1.5.2 */
-#define PNG_16_TO_8             0x0400
+#define PNG_16_TO_8             0x0400     /* Becomes 'chop' in 1.5.4 */
 #define PNG_RGBA                0x0800
 #define PNG_EXPAND              0x1000
 #define PNG_GAMMA               0x2000
@@ -295,10 +373,10 @@ typedef PNG_CONST png_uint_16p FAR * png_const_uint_16pp;
 #define PNG_RGB_TO_GRAY_ERR   0x200000L
 #define PNG_RGB_TO_GRAY_WARN  0x400000L
 #define PNG_RGB_TO_GRAY       0x600000L  /* two bits, RGB_TO_GRAY_ERR|WARN */
-#define PNG_ENCODE_ALPHA      0x800000L  /* Added to libpng-1.5.3 */
+#define PNG_ENCODE_ALPHA      0x800000L  /* Added to libpng-1.5.4 */
 #define PNG_ADD_ALPHA         0x1000000L  /* Added to libpng-1.2.7 */
 #define PNG_EXPAND_tRNS       0x2000000L  /* Added to libpng-1.2.9 */
-#define PNG_CHOP_16_TO_8      0x4000000L
+#define PNG_SCALE_16_TO_8     0x4000000L  /* Added to libpng-1.5.4 */
                        /*   0x8000000L  unused */
                        /*  0x10000000L  unused */
                        /*  0x20000000L  unused */
@@ -325,9 +403,9 @@ typedef PNG_CONST png_uint_16p FAR * png_const_uint_16pp;
 #define PNG_FLAG_CRC_ANCILLARY_NOWARN     0x0200
 #define PNG_FLAG_CRC_CRITICAL_USE         0x0400
 #define PNG_FLAG_CRC_CRITICAL_IGNORE      0x0800
-#define PNG_FLAG_ASSUME_sRGB              0x1000  /* Added to libpng-1.5.3 */
-#define PNG_FLAG_OPTIMIZE_ALPHA           0x2000  /* Added to libpng-1.5.3 */
-#define PNG_FLAG_DETECT_UNINITIALIZED     0x4000  /* Added to libpng-1.5.3 */
+#define PNG_FLAG_ASSUME_sRGB              0x1000  /* Added to libpng-1.5.4 */
+#define PNG_FLAG_OPTIMIZE_ALPHA           0x2000  /* Added to libpng-1.5.4 */
+#define PNG_FLAG_DETECT_UNINITIALIZED     0x4000  /* Added to libpng-1.5.4 */
 #define PNG_FLAG_KEEP_UNKNOWN_CHUNKS      0x8000L
 #define PNG_FLAG_KEEP_UNSAFE_CHUNKS       0x10000L
 #define PNG_FLAG_LIBRARY_MISMATCH         0x20000L
@@ -338,7 +416,7 @@ typedef PNG_CONST png_uint_16p FAR * png_const_uint_16pp;
                                   /*      0x400000L  unused */
 #define PNG_FLAG_BENIGN_ERRORS_WARN       0x800000L  /* Added to libpng-1.4.0 */
 #define PNG_FLAG_ZTXT_CUSTOM_STRATEGY    0x1000000L  /* 5 lines added */
-#define PNG_FLAG_ZTXT_CUSTOM_LEVEL       0x2000000L  /* to libpng-1.5.3 */
+#define PNG_FLAG_ZTXT_CUSTOM_LEVEL       0x2000000L  /* to libpng-1.5.4 */
 #define PNG_FLAG_ZTXT_CUSTOM_MEM_LEVEL   0x4000000L
 #define PNG_FLAG_ZTXT_CUSTOM_WINDOW_BITS 0x8000000L
 #define PNG_FLAG_ZTXT_CUSTOM_METHOD      0x10000000L
@@ -452,7 +530,7 @@ PNG_EXTERN png_fixed_point png_fixed PNGARG((png_structp png_ptr, double fp,
 #define PNG_tRNS PNG_CONST png_byte png_tRNS[5] = {116,  82,  78,  83, '\0'}
 #define PNG_zTXt PNG_CONST png_byte png_zTXt[5] = {122,  84,  88, 116, '\0'}
 
-/* Gamma values (new at libpng-1.5.3): */
+/* Gamma values (new at libpng-1.5.4): */
 #define PNG_GAMMA_MAC_OLD 151724  /* Assume '1.8' is really 2.2/1.45! */
 #define PNG_GAMMA_MAC_INVERSE 65909
 #define PNG_GAMMA_sRGB_INVERSE 45455
@@ -819,15 +897,13 @@ PNG_EXTERN void png_do_invert PNGARG((png_row_infop row_info,
     png_bytep row));
 #endif
 
-#ifdef PNG_READ_16_TO_8_SUPPORTED
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
 PNG_EXTERN void png_do_scale_16_to_8 PNGARG((png_row_infop row_info,
     png_bytep row));
-
-#ifdef PNG_READ_CHOP_16_TO_8_SUPPORTED
-PNG_EXTERN void png_do_chop PNGARG((png_row_infop row_info,
-    png_bytep row));
 #endif
-PNG_EXTERN void png_do_scale_16_to_8 PNGARG((png_row_infop row_info,
+
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+PNG_EXTERN void png_do_chop PNGARG((png_row_infop row_info,
     png_bytep row));
 #endif
 
@@ -1073,6 +1149,35 @@ PNG_EXTERN void png_64bit_product PNGARG((long v1, long v2,
     unsigned long *hi_product, unsigned long *lo_product));
 #endif
 
+#ifdef PNG_cHRM_SUPPORTED
+/* Added at libpng version 1.5.5 */
+typedef struct png_xy
+{
+   png_fixed_point redx, redy;
+   png_fixed_point greenx, greeny;
+   png_fixed_point bluex, bluey;
+   png_fixed_point whitex, whitey;
+} png_xy;
+
+typedef struct png_XYZ
+{
+   png_fixed_point redX, redY, redZ;
+   png_fixed_point greenX, greenY, greenZ;
+   png_fixed_point blueX, blueY, blueZ;
+} png_XYZ;
+
+/* The conversion APIs return 0 on success, non-zero on a parameter error. They
+ * allow conversion between the above representations of a color encoding.  When
+ * converting from XYZ end points to chromaticities the absolute magnitude of
+ * the end points is lost, when converting back the sum of the Y values of the
+ * three end points will be 1.0
+ */
+PNG_EXTERN int png_xy_from_XYZ PNGARG((png_xy *xy, png_XYZ XYZ));
+PNG_EXTERN int png_XYZ_from_xy PNGARG((png_XYZ *XYZ, png_xy xy));
+PNG_EXTERN int png_XYZ_from_xy_checked PNGARG((png_structp png_ptr,
+   png_XYZ *XYZ, png_xy xy));
+#endif
+
 /* Added at libpng version 1.4.0 */
 PNG_EXTERN void png_check_IHDR PNGARG((png_structp png_ptr,
     png_uint_32 width, png_uint_32 height, int bit_depth,
@@ -1135,7 +1240,7 @@ PNG_EXTERN png_charp png_format_number(png_const_charp start, png_charp end,
 #endif
 
 #ifdef PNG_WARNINGS_SUPPORTED
-/* New defines and members adding in libpng-1.5.3 */
+/* New defines and members adding in libpng-1.5.4 */
 #  define PNG_WARNING_PARAMETER_SIZE 32
 #  define PNG_WARNING_PARAMETER_COUNT 8
 
@@ -1228,8 +1333,18 @@ PNG_EXTERN void png_ascii_from_fixed PNGARG((png_structp png_ptr,
 #define PNG_FP_SAW_DOT   16  /* Saw a dot in current state */
 #define PNG_FP_SAW_E     32  /* Saw an E (or e) in current state */
 #define PNG_FP_SAW_ANY   60  /* Saw any of the above 4 */
+
+/* These three values don't affect the parser.  They are set but not used.
+ */
 #define PNG_FP_WAS_VALID 64  /* Preceding substring is a valid fp number */
-#define PNG_FP_INVALID  128  /* Available for callers as a distinct value */
+#define PNG_FP_NEGATIVE 128  /* A negative number, including "-0" */
+#define PNG_FP_NONZERO  256  /* A non-zero value */
+#define PNG_FP_STICKY   448  /* The above three flags */
+
+/* This is available for the caller to store in 'state' if required.  Do not
+ * call the parser after setting it (the parser sometimes clears it.)
+ */
+#define PNG_FP_INVALID  512  /* Available for callers as a distinct value */
 
 /* Result codes for the parser (boolean - true meants ok, false means
  * not ok yet.)
@@ -1237,6 +1352,20 @@ PNG_EXTERN void png_ascii_from_fixed PNGARG((png_structp png_ptr,
 #define PNG_FP_MAYBE      0  /* The number may be valid in the future */
 #define PNG_FP_OK         1  /* The number is valid */
 
+/* Tests on the sticky non-zero and negative flags.  To pass these checks
+ * the state must also indicate that the whole number is valid - this is
+ * achieved by testing PNG_FP_SAW_DIGIT (see the implementation for why this
+ * is equivalent to PNG_FP_OK above.)
+ */
+#define PNG_FP_NZ_MASK (PNG_FP_SAW_DIGIT | PNG_FP_NEGATIVE | PNG_FP_NONZERO)
+   /* NZ_MASK: the string is valid and a non-zero negative value */
+#define PNG_FP_Z_MASK (PNG_FP_SAW_DIGIT | PNG_FP_NONZERO)
+   /* Z MASK: the string is valid and a non-zero value. */
+   /* PNG_FP_SAW_DIGIT: the string is valid. */
+#define PNG_FP_IS_ZERO(state) (((state) & PNG_FP_Z_MASK) == PNG_FP_SAW_DIGIT)
+#define PNG_FP_IS_POSITIVE(state) (((state) & PNG_FP_NZ_MASK) == PNG_FP_Z_MASK)
+#define PNG_FP_IS_NEGATIVE(state) (((state) & PNG_FP_NZ_MASK) == PNG_FP_NZ_MASK)
+ 
 /* The actual parser.  This can be called repeatedly, it updates
  * the index into the string and the state variable (which must
  * be initialzed to 0).  It returns a result code, as above.  There
@@ -1256,7 +1385,10 @@ PNG_EXTERN int png_check_fp_number PNGARG((png_const_charp string,
     png_size_t size, int *statep, png_size_tp whereami));
 
 /* This is the same but it checks a complete string and returns true
- * only if it just contains a floating point number.
+ * only if it just contains a floating point number.  As of 1.5.4 this
+ * function also returns the state at the end of parsing the number if
+ * it was valid (otherwise it returns 0.)  This can be used for testing
+ * for negative or zero values using the sticky flag.
  */
 PNG_EXTERN int png_check_fp_string PNGARG((png_const_charp string,
     png_size_t size));

pngread.c

@@ -1,7 +1,7 @@
 
 /* pngread.c - read a PNG file
  *
- * Last changed in libpng 1.5.4 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.4 [July 7, 2011]
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -1286,9 +1286,23 @@ png_read_png(png_structp png_ptr, png_infop info_ptr,
 
    /* -------------- image transformations start here ------------------- */
 
-#ifdef PNG_READ_16_TO_8_SUPPORTED
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
    /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
     */
+   if (transforms & PNG_TRANSFORM_SCALE_16)
+   {
+     /* Added at libpng-1.5.4. "strip_16" produces the same result that it
+      * did in earlier versions, while "scale_16" is now more accurate.
+      */
+      png_set_scale_16(png_ptr);
+   }
+#endif
+
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+   /* If both SCALE and STRIP are required pngrtran will effectively cancel the
+    * latter by doing SCALE first.  This is ok and allows apps not to check for
+    * which is supported to get the right answer.
+    */
    if (transforms & PNG_TRANSFORM_STRIP_16)
       png_set_strip_16(png_ptr);
 #endif
@@ -1387,7 +1401,7 @@ png_read_png(png_structp png_ptr, png_infop info_ptr,
       png_set_gray_to_rgb(png_ptr);
 #endif
 
-/* Added at libpng-1.5.3 */
+/* Added at libpng-1.5.4 */
 #ifdef PNG_READ_EXPAND_16_SUPPORTED
    if (transforms & PNG_TRANSFORM_EXPAND_16)
       png_set_expand_16(png_ptr);

pngrtran.c

@@ -1,7 +1,7 @@
 
 /* pngrtran.c - transforms the data in a row for PNG readers
  *
- * Last changed in libpng 1.5.4 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.5 [(PENDING RELEASE)]
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -132,8 +132,25 @@ png_set_background(png_structp png_ptr,
 #  endif  /* FLOATING_POINT */
 #endif /* READ_BACKGROUND */
 
-#ifdef PNG_READ_16_TO_8_SUPPORTED
-/* Scale 16-bit depth files to 8-bit depth */
+/* Scale 16-bit depth files to 8-bit depth.  If both of these are set then the
+ * one that pngrtran does first (scale) happens.  This is necessary to allow the
+ * TRANSFORM and API behavior to be somewhat consistent, and it's simpler.
+ */
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+void PNGAPI
+png_set_scale_16(png_structp png_ptr)
+{
+   png_debug(1, "in png_set_scale_16");
+
+   if (png_ptr == NULL)
+      return;
+
+   png_ptr->transformations |= PNG_SCALE_16_TO_8;
+}
+#endif
+
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+/* Chop 16-bit depth files to 8-bit depth */
 void PNGAPI
 png_set_strip_16(png_structp png_ptr)
 {
@@ -143,26 +160,8 @@ png_set_strip_16(png_structp png_ptr)
       return;
 
    png_ptr->transformations |= PNG_16_TO_8;
-#ifdef PNG_READ_CHOP_16_TO_8_SUPPORTED
-   png_ptr->transformations &= ~PNG_CHOP_16_TO_8;
-#endif
-}
-
-#ifdef PNG_READ_CHOP_16_TO_8_SUPPORTED
-/* Chop 16-bit depth files to 8-bit depth */
-void PNGAPI
-png_set_chop_16(png_structp png_ptr)
-{
-   png_debug(1, "in png_set_chop_16");
-
-   if (png_ptr == NULL)
-      return;
-
-   png_ptr->transformations |= PNG_CHOP_16_TO_8;
-   png_ptr->transformations &= ~PNG_16_TO_8;
 }
 #endif
-#endif /* PNG_READ_16_TO_8_SUPPORTED */
 
 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
 void PNGAPI
@@ -775,12 +774,12 @@ png_set_gamma_fixed(png_structp png_ptr, png_fixed_point scrn_gamma,
    if (png_ptr == NULL)
       return;
 
-   /* New in libpng-1.5.3 - reserve particular negative values as flags. */
+   /* New in libpng-1.5.4 - reserve particular negative values as flags. */
    scrn_gamma = translate_gamma_flags(png_ptr, scrn_gamma, 1/*screen*/);
    file_gamma = translate_gamma_flags(png_ptr, file_gamma, 0/*file*/);
 
 #if PNG_LIBPNG_VER >= 10600
-   /* Checking the gamma values for being >0 was added in 1.5.3 along with the
+   /* Checking the gamma values for being >0 was added in 1.5.4 along with the
     * premultiplied alpha support; this actually hides an undocumented feature
     * of the previous implementation which allowed gamma processing to be
     * disabled in background handling.  There is no evidence (so far) that this
@@ -969,13 +968,17 @@ png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,
       {
          png_uint_16 red_int, green_int;
 
+         /* NOTE: this calculation does not round, but this behavior is retained
+          * for consistency, the inaccuracy is very small.  The code here always
+          * overwrites the coefficients, regardless of whether they have been
+          * defaulted or set already.
+          */
          red_int = (png_uint_16)(((png_uint_32)red*32768L)/100000L);
          green_int = (png_uint_16)(((png_uint_32)green*32768L)/100000L);
 
          png_ptr->rgb_to_gray_red_coeff   = red_int;
          png_ptr->rgb_to_gray_green_coeff = green_int;
-         png_ptr->rgb_to_gray_blue_coeff  =
-          (png_uint_16)(32768 - red_int - green_int);
+         png_ptr->rgb_to_gray_coefficients_set = 1;
       }
 
       else
@@ -984,17 +987,18 @@ png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,
             png_warning(png_ptr,
                "ignoring out of range rgb_to_gray coefficients");
 
-         /* Use the defaults, from the cHRM chunk if set, else the built in Rec
-          * 709 values (which correspond to sRGB, so we don't have to worry
-          * about the sRGB chunk!)
+         /* Use the defaults, from the cHRM chunk if set, else the historical
+          * values which are close to the sRGB/HDTV/ITU-Rec 709 values.  See
+          * png_do_rgb_to_gray for more discussion of the values.  In this case
+          * the coefficients are not marked as 'set' and are not overwritten if
+          * something has already provided a default.
           */
          if (png_ptr->rgb_to_gray_red_coeff == 0 &&
-            png_ptr->rgb_to_gray_green_coeff == 0 &&
-            png_ptr->rgb_to_gray_blue_coeff == 0)
+            png_ptr->rgb_to_gray_green_coeff == 0)
          {
-            png_ptr->rgb_to_gray_red_coeff   = 6968;  /* .212671 * 32768 + .5 */
-            png_ptr->rgb_to_gray_green_coeff = 23434; /* .715160 * 32768 + .5 */
-            png_ptr->rgb_to_gray_blue_coeff  = 2366;
+            png_ptr->rgb_to_gray_red_coeff   = 6968;
+            png_ptr->rgb_to_gray_green_coeff = 23434;
+            /* png_ptr->rgb_to_gray_blue_coeff  = 2366; */
          }
       }
    }
@@ -1155,7 +1159,7 @@ png_init_palette_transformations(png_structp png_ptr)
 static void /* PRIVATE */
 png_init_rgb_transformations(png_structp png_ptr)
 {
-   /* Added to libpng-1.5.3: check the color type to determine whether there
+   /* Added to libpng-1.5.4: check the color type to determine whether there
     * is any alpha or transparency in the image and simply cancel the
     * background and alpha mode stuff if there isn't.
     */
@@ -1260,9 +1264,9 @@ png_init_read_transformations(png_structp png_ptr)
     */
 
 #ifdef PNG_READ_GAMMA_SUPPORTED
-   /* Prior to 1.5.3 these tests were performed from png_set_gamma, 1.5.3 adds
+   /* Prior to 1.5.4 these tests were performed from png_set_gamma, 1.5.4 adds
     * png_set_alpha_mode and this is another source for a default file gamma so
-    * the test needs to be performed later - here.  In addition prior to 1.5.3
+    * the test needs to be performed later - here.  In addition prior to 1.5.4
     * the tests were repeated for the PALETTE color type here - this is no
     * longer necessary (and doesn't seem to have been necessary before.)
     */
@@ -1287,7 +1291,7 @@ png_init_read_transformations(png_structp png_ptr)
 
       else if (png_ptr->screen_gamma != 0)
          /* The converse - assume the file matches the screen, note that this
-          * perhaps undesireable default can (from 1.5.3) be changed by calling
+          * perhaps undesireable default can (from 1.5.4) be changed by calling
           * png_set_alpha_mode (even if the alpha handling mode isn't required
           * or isn't changed from the default.)
           */
@@ -1297,7 +1301,7 @@ png_init_read_transformations(png_structp png_ptr)
          /* Just in case the following prevents any processing - file and screen
           * are both assumed to be linear and there is no way to introduce a
           * third gamma value other than png_set_background with 'UNIQUE', and,
-          * prior to 1.5.3
+          * prior to 1.5.4
           */
          png_ptr->screen_gamma = png_ptr->gamma = PNG_FP_1;
 
@@ -1330,20 +1334,21 @@ png_init_read_transformations(png_structp png_ptr)
     *  6) PNG_GAMMA
     *  7) PNG_STRIP_ALPHA (if compose)
     *  8) PNG_ENCODE_ALPHA
-    *  9) PNG_16_TO_8 or PNG_CHOP_16_TO_8 (strip16/chop16)
-    * 10) PNG_QUANTIZE (converts to palette)
-    * 11) PNG_EXPAND_16
-    * 12) PNG_GRAY_TO_RGB iff PNG_BACKGROUND_IS_GRAY
-    * 13) PNG_INVERT_MONO
-    * 14) PNG_SHIFT
-    * 15) PNG_PACK
-    * 16) PNG_BGR
-    * 17) PNG_PACKSWAP
-    * 18) PNG_FILLER (includes PNG_ADD_ALPHA)
-    * 19) PNG_INVERT_ALPHA
-    * 20) PNG_SWAP_ALPHA
-    * 21) PNG_SWAP_BYTES
-    * 22) PNG_USER_TRANSFORM [must be last]
+    *  9) PNG_SCALE_16_TO_8
+    * 10) PNG_16_TO_8
+    * 11) PNG_QUANTIZE (converts to palette)
+    * 12) PNG_EXPAND_16
+    * 13) PNG_GRAY_TO_RGB iff PNG_BACKGROUND_IS_GRAY
+    * 14) PNG_INVERT_MONO
+    * 15) PNG_SHIFT
+    * 16) PNG_PACK
+    * 17) PNG_BGR
+    * 18) PNG_PACKSWAP
+    * 19) PNG_FILLER (includes PNG_ADD_ALPHA)
+    * 20) PNG_INVERT_ALPHA
+    * 21) PNG_SWAP_ALPHA
+    * 22) PNG_SWAP_BYTES
+    * 23) PNG_USER_TRANSFORM [must be last]
     */
 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
    if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
@@ -1358,12 +1363,12 @@ png_init_read_transformations(png_structp png_ptr)
          PNG_EXPAND_tRNS);
       png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
 
-      /* Kill the tRNS chunk itself too.  Prior to 1.5.3 this did not happen
+      /* Kill the tRNS chunk itself too.  Prior to 1.5.4 this did not happen
        * so transparency information would remain just so long as it wasn't
        * expanded.  This produces unexpected API changes if the set of things
        * that do PNG_EXPAND_tRNS changes (perfectly possible given the
        * documentation - which says ask for what you want, accept what you
-       * get.)  This makes the behavior consistent from 1.5.3:
+       * get.)  This makes the behavior consistent from 1.5.4:
        */
       png_ptr->num_trans = 0;
    }
@@ -1401,7 +1406,7 @@ png_init_read_transformations(png_structp png_ptr)
    if (png_ptr->transformations & PNG_BACKGROUND_EXPAND)
    {
       /* PNG_BACKGROUND_EXPAND: the background is in the file color space, so if
-       * the file was greyscale the background value is gray.
+       * the file was grayscale the background value is gray.
        */
       if (!(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
          png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
@@ -1456,28 +1461,16 @@ png_init_read_transformations(png_structp png_ptr)
        *
        * The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at
        * present, so that case is ok (until do_expand_16 is moved.)
+       *
+       * NOTE: this discards the low 16 bits of the user supplied background
+       * color, but until expand_16 works properly there is no choice!
        */
-
-      if (png_ptr->transformations & PNG_16_TO_8)
-      {
 #     define CHOP(x) (x)=((png_uint_16)(((png_uint_32)(x)*255+32895) >> 16))
       CHOP(png_ptr->background.red);
       CHOP(png_ptr->background.green);
       CHOP(png_ptr->background.blue);
       CHOP(png_ptr->background.gray);
 #     undef CHOP
-      }
-#ifdef PNG_READ_CHOP_16_TO_8_SUPPORTED
-      else /* Use pre-libpng-1.5.4 inaccurate "ACCURATE" scaling */
-      {
-#     define CHOP(x) (x)=((png_uint_16)((2*(png_uint_32)(x) + 257)/514))
-      CHOP(png_ptr->background.red);
-      CHOP(png_ptr->background.green);
-      CHOP(png_ptr->background.blue);
-      CHOP(png_ptr->background.gray);
-#     undef CHOP
-      }
-#endif /* PNG_READ_CHOP_16_TO_8_SUPPORTED */
    }
 #endif /* PNG_READ_BACKGROUND_SUPPORTED && PNG_READ_EXPAND_16_SUPPORTED */
 
@@ -1485,7 +1478,7 @@ png_init_read_transformations(png_structp png_ptr)
     * background support (see the comments in scripts/pnglibconf.dfa), this
     * allows pre-multiplication of the alpha channel to be implemented as
     * compositing on black.  This is probably sub-optimal and has been done in
-    * 1.5.3 betas simply to enable external critique and testing (i.e. to
+    * 1.5.4 betas simply to enable external critique and testing (i.e. to
     * implement the new API quickly, without lots of internal changes.)
     */
 
@@ -1504,7 +1497,7 @@ png_init_read_transformations(png_structp png_ptr)
     * the gamma tables will not be built even if composition is required on a
     * gamma encoded value.
     *
-    * In 1.5.3 this is addressed below by an additional check on the individual
+    * In 1.5.4 this is addressed below by an additional check on the individual
     * file gamma - if it is not 1.0 both RGB_TO_GRAY and COMPOSE need the
     * tables.
     */
@@ -1515,9 +1508,11 @@ png_init_read_transformations(png_structp png_ptr)
       || ((png_ptr->transformations & PNG_COMPOSE)
          && (png_gamma_significant(png_ptr->gamma)
             || png_gamma_significant(png_ptr->screen_gamma)
+#  ifdef PNG_READ_BACKGROUND_SUPPORTED
             || (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_UNIQUE
-               && png_gamma_significant(png_ptr->background_gamma))))
-      || ((png_ptr->transformations & PNG_ENCODE_ALPHA)
+               && png_gamma_significant(png_ptr->background_gamma))
+#  endif
+      )) || ((png_ptr->transformations & PNG_ENCODE_ALPHA)
          && png_gamma_significant(png_ptr->screen_gamma))
       )
    {
@@ -1870,7 +1865,7 @@ png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
 #endif
 
 #ifdef PNG_READ_GAMMA_SUPPORTED
-   /* The following used to be conditional on PNG_GAMMA (prior to 1.5.3),
+   /* The following used to be conditional on PNG_GAMMA (prior to 1.5.4),
     * however it seems that the code in png_init_read_transformations, which has
     * been called before this from png_read_update_info->png_read_start_row
     * sometimes does the gamma transform and cancels the flag.
@@ -1878,21 +1873,43 @@ png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
    info_ptr->gamma = png_ptr->gamma;
 #endif
 
-#ifdef PNG_READ_16_TO_8_SUPPORTED
-#ifdef PNG_READ_16BIT_SUPPORTED
-   if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_CHOP_16_TO_8)) &&
-       (info_ptr->bit_depth == 16))
-      info_ptr->bit_depth = 8;
-#else
-   /* Force chopping 16-bit input down to 8 */
    if (info_ptr->bit_depth == 16)
    {
-      if (!(png_ptr->transformations & PNG_CHOP_16_TO_8))
-        png_ptr->transformations |=PNG_16_TO_8;
-      info_ptr->bit_depth = 8;
+#  ifdef PNG_READ_16BIT_SUPPORTED
+#     ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+         if (png_ptr->transformations & PNG_SCALE_16_TO_8)
+            info_ptr->bit_depth = 8;
+#     endif
+
+#     ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+         if (png_ptr->transformations & PNG_16_TO_8)
+            info_ptr->bit_depth = 8;
+#     endif
+
+#  else
+      /* No 16 bit support: force chopping 16-bit input down to 8, in this case
+       * the app program can chose if both APIs are available by setting the
+       * correct scaling to use.
+       */
+#     ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+         /* For compatibility with previous versions use the strip method by
+          * default.  This code works because if PNG_SCALE_16_TO_8 is already
+          * set the code below will do that in preference to the chop.
+          */
+         png_ptr->transformations |= PNG_16_TO_8;
+         info_ptr->bit_depth = 8;
+#     else
+
+#        if PNG_READ_SCALE_16_TO_8_SUPPORTED
+            png_ptr->transformations |= PNG_SCALE_16_TO_8;
+            info_ptr->bit_depth = 8;
+#        else
+
+            CONFIGURATION ERROR: you must enable at least one 16 to 8 method
+#        endif
+#    endif
+#endif /* !READ_16BIT_SUPPORTED */
    }
-#endif
-#endif
 
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    if (png_ptr->transformations & PNG_GRAY_TO_RGB)
@@ -1979,7 +1996,7 @@ defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
 
    info_ptr->rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth, info_ptr->width);
 
-   /* Adding in 1.5.3: cache the above value in png_struct so that we can later
+   /* Adding in 1.5.4: cache the above value in png_struct so that we can later
     * check in png_rowbytes that the user buffer won't get overwritten.  Note
     * that the field is not always set - if png_read_update_info isn't called
     * the application has to either not do any transforms or get the calculation
@@ -2004,15 +2021,15 @@ png_do_read_transformations(png_structp png_ptr)
 
    if (png_ptr->row_buf == NULL)
    {
-      /* Prior to 1.5.3 this output row/pass where the NULL pointer is, but this
+      /* Prior to 1.5.4 this output row/pass where the NULL pointer is, but this
        * error is incredibly rare and incredibly easy to debug without this
        * information.
        */
       png_error(png_ptr, "NULL row buffer");
    }
 
-   /* The following is debugging; prior to 1.5.3 the code was never compiled in;
-    * in 1.5.3 PNG_FLAG_DETECT_UNINITIALIZED was added and the macro
+   /* The following is debugging; prior to 1.5.4 the code was never compiled in;
+    * in 1.5.4 PNG_FLAG_DETECT_UNINITIALIZED was added and the macro
     * PNG_WARN_UNINITIALIZED_ROW removed.  In 1.5 the new flag is set only for
     * selected new APIs to ensure that there is no API change.
     */
@@ -2021,7 +2038,7 @@ png_do_read_transformations(png_structp png_ptr)
    {
       /* Application has failed to call either png_read_start_image() or
        * png_read_update_info() after setting transforms that expand pixels.
-       * This check added to libpng-1.2.19 (but not enabled until 1.5.3).
+       * This check added to libpng-1.2.19 (but not enabled until 1.5.4).
        */
       png_error(png_ptr, "Uninitialized row");
    }
@@ -2152,13 +2169,18 @@ png_do_read_transformations(png_structp png_ptr)
       png_do_encode_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1, png_ptr);
 #endif
 
-#ifdef PNG_READ_16_TO_8_SUPPORTED
-   if (png_ptr->transformations & PNG_16_TO_8)
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+   if (png_ptr->transformations & PNG_SCALE_16_TO_8)
       png_do_scale_16_to_8(&(png_ptr->row_info), png_ptr->row_buf + 1);
-#  ifdef PNG_READ_CHOP_16_TO_8_SUPPORTED
-   else if (png_ptr->transformations & PNG_CHOP_16_TO_8)
+#endif
+
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+   /* There is no harm in doing both of these because only one has any effect,
+    * by putting the 'scale' option first if the app asks for scale (either by
+    * calling the API or in a TRANSFORM flag) this is what happens.
+    */
+   if (png_ptr->transformations & PNG_16_TO_8)
       png_do_chop(&(png_ptr->row_info), png_ptr->row_buf + 1);
-#  endif
 #endif
 
 #ifdef PNG_READ_QUANTIZE_SUPPORTED
@@ -2183,7 +2205,7 @@ png_do_read_transformations(png_structp png_ptr)
 #endif
 
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
-   /*NOTE: moved here in 1.5.3 (from much later in this list.) */
+   /*NOTE: moved here in 1.5.4 (from much later in this list.) */
    if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
        (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
       png_do_gray_to_rgb(&(png_ptr->row_info), png_ptr->row_buf + 1);
@@ -2487,7 +2509,7 @@ png_do_unshift(png_row_infop row_info, png_bytep row,
 }
 #endif
 
-#ifdef PNG_READ_16_TO_8_SUPPORTED
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
 /* Scale rows of bit depth 16 down to 8 accurately */
 void /* PRIVATE */
 png_do_scale_16_to_8(png_row_infop row_info, png_bytep row)
@@ -2544,7 +2566,9 @@ png_do_scale_16_to_8(png_row_infop row_info, png_bytep row)
       row_info->rowbytes = row_info->width * row_info->channels;
    }
 }
+#endif
 
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
 void /* PRIVATE */
 /* Simply discard the low byte.  This was the default behavior prior
  * to libpng-1.5.4.
@@ -2561,8 +2585,8 @@ png_do_chop(png_row_infop row_info, png_bytep row)
 
       while (sp < ep)
       {
-         *dp++ = *sp++;
-         sp++;
+         *dp++ = *sp;
+         sp += 2; /* skip low byte */
       }
 
       row_info->bit_depth = 8;
@@ -2570,7 +2594,7 @@ png_do_chop(png_row_infop row_info, png_bytep row)
       row_info->rowbytes = row_info->width * row_info->channels;
    }
 }
-#endif /* PNG_READ_16_TO_8_SUPPORTED */
+#endif
 
 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
 void /* PRIVATE */
@@ -3047,33 +3071,61 @@ png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
 
 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
 /* Reduce RGB files to grayscale, with or without alpha
- * using the equation given in Poynton's ColorFAQ at
- * <http://www.inforamp.net/~poynton/>  (THIS LINK IS DEAD June 2008)
- * New link:
- * <http://www.poynton.com/notes/colour_and_gamma/>
+ * using the equation given in Poynton's ColorFAQ of 1998-01-04 at
+ * <http://www.inforamp.net/~poynton/>  (THIS LINK IS DEAD June 2008 but
+ * versions dated 1998 through November 2002 have been archived at
+ * http://web.archive.org/web/20000816232553/http://www.inforamp.net/
+ * ~poynton/notes/colour_and_gamma/ColorFAQ.txt )
  * Charles Poynton poynton at poynton.com
  *
  *     Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
  *
- *  We approximate this with
- *
- *     Y = 0.21268 * R    + 0.7151 * G    + 0.07217 * B
- *
  *  which can be expressed with integers as
  *
  *     Y = (6969 * R + 23434 * G + 2365 * B)/32768
  *
- *  The calculation is to be done in a linear colorspace.
+ * Poynton's current link (as of January 2003 through July 2011):
+ * <http://www.poynton.com/notes/colour_and_gamma/>
+ * has changed the numbers slightly:
  *
- *  Other integer coefficents can be used via png_set_rgb_to_gray().
+ *     Y = 0.2126*R + 0.7152*G + 0.0722*B
+ *
+ *  which can be expressed with integers as
+ *
+ *     Y = (6966 * R + 23436 * G + 2366 * B)/32768
+ *
+ *  Historically, however, libpng uses numbers derived from the ITU-R Rec 709
+ *  end point chromaticities and the D65 white point.  Depending on the
+ *  precision used for the D65 white point this produces a variety of different
+ *  numbers, however if the four decimal place value used in ITU-R Rec 709 is
+ *  used (0.3127,0.3290) the Y calculation would be:
+ *
+ *     Y = (6968 * R + 23435 * G + 2366 * B)/32768
+ *
+ *  While this is correct the rounding results in an overflow for white, because
+ *  the sum of the rounded coefficients is 32769, not 32768.  Consequently
+ *  libpng uses, instead, the closest non-overflowing approximation:
+ *
+ *     Y = (6968 * R + 23434 * G + 2366 * B)/32768
+ *
+ *  Starting with libpng-1.5.5, if the image being converted has a cHRM chunk
+ *  (including an sRGB chunk) then the chromaticities are used to calculate the
+ *  coefficients.  See the chunk handling in pngrutil.c for more information.
+ *
+ *  In all cases the calculation is to be done in a linear colorspace.  If no
+ *  gamma information is available to correct the encoding of the original RGB
+ *  values this results in an implicit assumption that the original PNG RGB
+ *  values were linear.
+ *
+ *  Other integer coefficents can be used via png_set_rgb_to_gray().  Because
+ *  the API takes just red and green coefficients the blue coefficient is
+ *  calculated to make the sum 32768.  This will result in different rounding
+ *  to that used above.
  */
 int /* PRIVATE */
 png_do_rgb_to_gray(png_structp png_ptr, png_row_infop row_info, png_bytep row)
 
 {
-   png_uint_32 i;
-
-   png_uint_32 row_width = row_info->width;
    int rgb_error = 0;
 
    png_debug(1, "in png_do_rgb_to_gray");
@@ -3081,234 +3133,179 @@ png_do_rgb_to_gray(png_structp png_ptr, png_row_infop row_info, png_bytep row)
    if (!(row_info->color_type & PNG_COLOR_MASK_PALETTE) &&
        (row_info->color_type & PNG_COLOR_MASK_COLOR))
    {
-      png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
-      png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
-      png_uint_32 bc = png_ptr->rgb_to_gray_blue_coeff;
+      PNG_CONST png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
+      PNG_CONST png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
+      PNG_CONST png_uint_32 bc = 32768 - rc - gc;
+      PNG_CONST png_uint_32 row_width = row_info->width;
+      PNG_CONST int have_alpha =
+         (row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
 
-      if (row_info->color_type == PNG_COLOR_TYPE_RGB)
+      if (row_info->bit_depth == 8)
       {
-         if (row_info->bit_depth == 8)
-         {
 #if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
-            if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
+         /* Notice that gamma to/from 1 are not necessarily inverses (if
+          * there is an overall gamma correction).  Prior to 1.5.5 this code
+          * checked the linearized values for equality; this doesn't match
+          * the documentation, the original values must be checked.
+          */
+         if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
+         {
+            png_bytep sp = row;
+            png_bytep dp = row;
+            png_uint_32 i;
+
+            for (i = 0; i < row_width; i++)
             {
-               png_bytep sp = row;
-               png_bytep dp = row;
+               png_byte red   = *(sp++);
+               png_byte green = *(sp++);
+               png_byte blue  = *(sp++);
 
-               for (i = 0; i < row_width; i++)
+               if (red != green || red != blue)
                {
-                  png_byte red   = png_ptr->gamma_to_1[*(sp++)];
-                  png_byte green = png_ptr->gamma_to_1[*(sp++)];
-                  png_byte blue  = png_ptr->gamma_to_1[*(sp++)];
+                  red = png_ptr->gamma_to_1[red];
+                  green = png_ptr->gamma_to_1[green];
+                  blue = png_ptr->gamma_to_1[blue];
 
-                  if (red != green || red != blue)
-                  {
-                     rgb_error |= 1;
-                     *(dp++) = png_ptr->gamma_from_1[
-                         (rc*red + gc*green + bc*blue)>>15];
-                  }
-
-                  else
-                     *(dp++) = *(sp - 1);
+                  rgb_error |= 1;
+                  *(dp++) = png_ptr->gamma_from_1[
+                      (rc*red + gc*green + bc*blue + 16384)>>15];
                }
-            }
-            else
-#endif
-            {
-               png_bytep sp = row;
-               png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
+
+               else
                {
-                  png_byte red   = *(sp++);
-                  png_byte green = *(sp++);
-                  png_byte blue  = *(sp++);
+                  /* If there is no overall correction the table will not be
+                   * set.
+                   */
+                  if (png_ptr->gamma_table != NULL)
+                     red = png_ptr->gamma_table[red];
 
-                  if (red != green || red != blue)
-                  {
-                     rgb_error |= 1;
-                     *(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
-                  }
-
-                  else
-                     *(dp++) = *(sp - 1);
+                  *(dp++) = red;
                }
+
+               if (have_alpha)
+                  *(dp++) = *(sp++);
             }
          }
-
-         else /* RGB bit_depth == 16 */
+         else
+#endif
          {
-#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
-            if (png_ptr->gamma_16_to_1 != NULL &&
-                png_ptr->gamma_16_from_1 != NULL)
+            png_bytep sp = row;
+            png_bytep dp = row;
+            png_uint_32 i;
+
+            for (i = 0; i < row_width; i++)
             {
-               png_bytep sp = row;
-               png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
+               png_byte red   = *(sp++);
+               png_byte green = *(sp++);
+               png_byte blue  = *(sp++);
+
+               if (red != green || red != blue)
                {
-                  png_uint_16 red, green, blue, w;
+                  rgb_error |= 1;
+                  /*NOTE: this is the historical approach which simply
+                   * truncates the results.
+                   */
+                  *(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
+               }
 
-                  red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               else
+                  *(dp++) = red;
 
-                  if (red == green && red == blue)
-                     w = red;
+               if (have_alpha)
+                  *(dp++) = *(sp++);
+            }
+         }
+      }
 
-                  else
-                  {
-                     png_uint_16 red_1   = png_ptr->gamma_16_to_1[(red&0xff)
+      else /* RGB bit_depth == 16 */
+      {
+#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
+         if (png_ptr->gamma_16_to_1 != NULL && png_ptr->gamma_16_from_1 != NULL)
+         {
+            png_bytep sp = row;
+            png_bytep dp = row;
+            png_uint_32 i;
+
+            for (i = 0; i < row_width; i++)
+            {
+               png_uint_16 red, green, blue, w;
+
+               red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+
+               if (red == green && red == blue)
+               {
+                  if (png_ptr->gamma_16_table != NULL)
+                     w = png_ptr->gamma_16_table[(red&0xff)
                          >> png_ptr->gamma_shift][red>>8];
-                     png_uint_16 green_1 =
-                         png_ptr->gamma_16_to_1[(green&0xff) >>
-                         png_ptr->gamma_shift][green>>8];
-                     png_uint_16 blue_1  = png_ptr->gamma_16_to_1[(blue&0xff)
-                         >> png_ptr->gamma_shift][blue>>8];
-                     png_uint_16 gray16  = (png_uint_16)((rc*red_1 + gc*green_1
-                         + bc*blue_1)>>15);
-                     w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
-                         png_ptr->gamma_shift][gray16 >> 8];
-                     rgb_error |= 1;
-                  }
-
-                  *(dp++) = (png_byte)((w>>8) & 0xff);
-                  *(dp++) = (png_byte)(w & 0xff);
-               }
-            }
-            else
-#endif
-            {
-               png_bytep sp = row;
-               png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
-               {
-                  png_uint_16 red, green, blue, gray16;
-
-                  red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-
-                  if (red != green || red != blue)
-                     rgb_error |= 1;
-
-                  gray16  = (png_uint_16)((rc*red + gc*green + bc*blue)>>15);
-                  *(dp++) = (png_byte)((gray16>>8) & 0xff);
-                  *(dp++) = (png_byte)(gray16 & 0xff);
-               }
-            }
-         }
-      }
-      if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
-      {
-         if (row_info->bit_depth == 8)
-         {
-#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
-            if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
-            {
-               png_bytep sp = row;
-               png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
-               {
-                  png_byte red   = png_ptr->gamma_to_1[*(sp++)];
-                  png_byte green = png_ptr->gamma_to_1[*(sp++)];
-                  png_byte blue  = png_ptr->gamma_to_1[*(sp++)];
-
-                  if (red != green || red != blue)
-                     rgb_error |= 1;
-
-                  *(dp++) =  png_ptr->gamma_from_1
-                      [(rc*red + gc*green + bc*blue)>>15];
-
-                  *(dp++) = *(sp++);  /* alpha */
-               }
-            }
-            else
-#endif
-            {
-               png_bytep sp = row;
-               png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
-               {
-                  png_byte red   = *(sp++);
-                  png_byte green = *(sp++);
-                  png_byte blue  = *(sp++);
-                  if (red != green || red != blue)
-                     rgb_error |= 1;
-
-                  *(dp++) =  (png_byte)((rc*red + gc*green + bc*blue)>>15);
-                  *(dp++) = *(sp++);  /* alpha */
-               }
-            }
-         }
-         else /* RGBA bit_depth == 16 */
-         {
-#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
-            if (png_ptr->gamma_16_to_1 != NULL &&
-                png_ptr->gamma_16_from_1 != NULL)
-            {
-               png_bytep sp = row;
-               png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
-               {
-                  png_uint_16 red, green, blue, w;
-
-                  red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-
-                  if (red == green && red == blue)
-                     w = red;
 
                   else
-                  {
-                     png_uint_16 red_1   = png_ptr->gamma_16_to_1[(red&0xff) >>
-                         png_ptr->gamma_shift][red>>8];
+                     w = red;
+               }
 
-                     png_uint_16 green_1 =
-                         png_ptr->gamma_16_to_1[(green&0xff) >>
-                         png_ptr->gamma_shift][green>>8];
+               else
+               {
+                  png_uint_16 red_1   = png_ptr->gamma_16_to_1[(red&0xff)
+                      >> png_ptr->gamma_shift][red>>8];
+                  png_uint_16 green_1 =
+                      png_ptr->gamma_16_to_1[(green&0xff) >>
+                      png_ptr->gamma_shift][green>>8];
+                  png_uint_16 blue_1  = png_ptr->gamma_16_to_1[(blue&0xff)
+                      >> png_ptr->gamma_shift][blue>>8];
+                  png_uint_16 gray16  = (png_uint_16)((rc*red_1 + gc*green_1
+                      + bc*blue_1 + 16384)>>15);
+                  w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
+                      png_ptr->gamma_shift][gray16 >> 8];
+                  rgb_error |= 1;
+               }
 
-                     png_uint_16 blue_1  = png_ptr->gamma_16_to_1[(blue&0xff) >>
-                         png_ptr->gamma_shift][blue>>8];
+               *(dp++) = (png_byte)((w>>8) & 0xff);
+               *(dp++) = (png_byte)(w & 0xff);
 
-                     png_uint_16 gray16  = (png_uint_16)((rc * red_1
-                         + gc * green_1 + bc * blue_1)>>15);
-
-                     w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
-                         png_ptr->gamma_shift][gray16 >> 8];
-
-                     rgb_error |= 1;
-                  }
-
-                  *(dp++) = (png_byte)((w>>8) & 0xff);
-                  *(dp++) = (png_byte)(w & 0xff);
-                  *(dp++) = *(sp++);  /* alpha */
+               if (have_alpha)
+               {
+                  *(dp++) = *(sp++);
                   *(dp++) = *(sp++);
                }
             }
-            else
+         }
+         else
 #endif
+         {
+            png_bytep sp = row;
+            png_bytep dp = row;
+            png_uint_32 i;
+
+            for (i = 0; i < row_width; i++)
             {
-               png_bytep sp = row;
-               png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
+               png_uint_16 red, green, blue, gray16;
+
+               red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+
+               if (red != green || red != blue)
+                  rgb_error |= 1;
+
+               /* From 1.5.5 in the 16 bit case do the accurate convertion even
+                * in the 'fast' case - this is because this is where the code
+                * ends up when handling linear 16 bit data.
+                */
+               gray16  = (png_uint_16)((rc*red + gc*green + bc*blue + 16384) >>
+                  15);
+               *(dp++) = (png_byte)((gray16>>8) & 0xff);
+               *(dp++) = (png_byte)(gray16 & 0xff);
+
+               if (have_alpha)
                {
-                  png_uint_16 red, green, blue, gray16;
-                  red   = (png_uint_16)((*(sp)<<8) | *(sp + 1)); sp += 2;
-                  green = (png_uint_16)((*(sp)<<8) | *(sp + 1)); sp += 2;
-                  blue  = (png_uint_16)((*(sp)<<8) | *(sp + 1)); sp += 2;
-
-                  if (red != green || red != blue)
-                     rgb_error |= 1;
-
-                  gray16  = (png_uint_16)((rc*red + gc*green + bc*blue)>>15);
-                  *(dp++) = (png_byte)((gray16>>8) & 0xff);
-                  *(dp++) = (png_byte)(gray16 & 0xff);
-                  *(dp++) = *(sp++);  /* alpha */
+                  *(dp++) = *(sp++);
                   *(dp++) = *(sp++);
                }
             }
          }
       }
+
       row_info->channels -= 2;
       row_info->color_type = (png_byte)(row_info->color_type &
           ~PNG_COLOR_MASK_COLOR);
@@ -4464,7 +4461,7 @@ png_do_expand_palette(png_row_infop row_info, png_bytep row,
       if (row_info->bit_depth == 8)
       {
          {
-            if (trans_alpha != NULL)
+            if (num_trans > 0)
             {
                sp = row + (png_size_t)row_width - 1;
                dp = row + (png_size_t)(row_width << 2) - 1;
@@ -4518,7 +4515,7 @@ png_do_expand_palette(png_row_infop row_info, png_bytep row,
  */
 void /* PRIVATE */
 png_do_expand(png_row_infop row_info, png_bytep row,
-    png_const_color_16p trans_value)
+    png_const_color_16p trans_color)
 {
    int shift, value;
    png_bytep sp, dp;
@@ -4530,7 +4527,7 @@ png_do_expand(png_row_infop row_info, png_bytep row,
    {
       if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
       {
-         png_uint_16 gray = (png_uint_16)(trans_value ? trans_value->gray : 0);
+         png_uint_16 gray = (png_uint_16)(trans_color ? trans_color->gray : 0);
 
          if (row_info->bit_depth < 8)
          {
@@ -4622,7 +4619,7 @@ png_do_expand(png_row_infop row_info, png_bytep row,
             row_info->rowbytes = row_width;
          }
 
-         if (trans_value != NULL)
+         if (trans_color != NULL)
          {
             if (row_info->bit_depth == 8)
             {
@@ -4674,13 +4671,13 @@ png_do_expand(png_row_infop row_info, png_bytep row,
                row_width);
          }
       }
-      else if (row_info->color_type == PNG_COLOR_TYPE_RGB && trans_value)
+      else if (row_info->color_type == PNG_COLOR_TYPE_RGB && trans_color)
       {
          if (row_info->bit_depth == 8)
          {
-            png_byte red = (png_byte)(trans_value->red & 0xff);
-            png_byte green = (png_byte)(trans_value->green & 0xff);
-            png_byte blue = (png_byte)(trans_value->blue & 0xff);
+            png_byte red = (png_byte)(trans_color->red & 0xff);
+            png_byte green = (png_byte)(trans_color->green & 0xff);
+            png_byte blue = (png_byte)(trans_color->blue & 0xff);
             sp = row + (png_size_t)row_info->rowbytes - 1;
             dp = row + (png_size_t)(row_width << 2) - 1;
             for (i = 0; i < row_width; i++)
@@ -4698,12 +4695,12 @@ png_do_expand(png_row_infop row_info, png_bytep row,
          }
          else if (row_info->bit_depth == 16)
          {
-            png_byte red_high = (png_byte)((trans_value->red >> 8) & 0xff);
-            png_byte green_high = (png_byte)((trans_value->green >> 8) & 0xff);
-            png_byte blue_high = (png_byte)((trans_value->blue >> 8) & 0xff);
-            png_byte red_low = (png_byte)(trans_value->red & 0xff);
-            png_byte green_low = (png_byte)(trans_value->green & 0xff);
-            png_byte blue_low = (png_byte)(trans_value->blue & 0xff);
+            png_byte red_high = (png_byte)((trans_color->red >> 8) & 0xff);
+            png_byte green_high = (png_byte)((trans_color->green >> 8) & 0xff);
+            png_byte blue_high = (png_byte)((trans_color->blue >> 8) & 0xff);
+            png_byte red_low = (png_byte)(trans_color->red & 0xff);
+            png_byte green_low = (png_byte)(trans_color->green & 0xff);
+            png_byte blue_low = (png_byte)(trans_color->blue & 0xff);
             sp = row + row_info->rowbytes - 1;
             dp = row + (png_size_t)(row_width << 3) - 1;
             for (i = 0; i < row_width; i++)
@@ -4743,7 +4740,7 @@ png_do_expand(png_row_infop row_info, png_bytep row,
 #endif
 
 #ifdef PNG_READ_EXPAND_16_SUPPORTED
-/* If the bit depth is 8 and the colour type is not a palette type expand the
+/* If the bit depth is 8 and the color type is not a palette type expand the
  * whole row to 16 bits.  Has no effect otherwise.
  */
 void /* PRIVATE */

pngrutil.c

@@ -1,7 +1,7 @@
 
 /* pngrutil.c - utilities to read a PNG file
  *
- * Last changed in libpng 1.5.4 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.5 [(PENDING RELEASE)]
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -458,7 +458,7 @@ png_decompress_chunk(png_structp png_ptr, int comp_type,
       {
          /* Success (maybe) - really uncompress the chunk. */
          png_size_t new_size = 0;
-         png_charp text = png_malloc_warn(png_ptr,
+         png_charp text = (png_charp)png_malloc_warn(png_ptr,
              prefix_size + expanded_size + 1);
 
          if (text != NULL)
@@ -501,7 +501,7 @@ png_decompress_chunk(png_structp png_ptr, int comp_type,
     * amount of compressed data.
     */
    {
-      png_charp text = png_malloc_warn(png_ptr, prefix_size + 1);
+      png_charp text = (png_charp)png_malloc_warn(png_ptr, prefix_size + 1);
 
       if (text != NULL)
       {
@@ -1022,27 +1022,80 @@ png_handle_cHRM(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
    /* Store the _white values as default coefficients for the rgb to gray
-    * operation if it is supported.
+    * operation if it is supported.  Check if the transform is already set to
+    * avoid destroying the transform values.
     */
-   if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
+   if (!png_ptr->rgb_to_gray_coefficients_set)
    {
-      /* png_set_background has not been called, the coefficients must be in
-       * range for the following to work without overflow.
+      /* png_set_background has not been called and we haven't seen an sRGB
+       * chunk yet.  Find the XYZ of the three end points.
        */
-      if (y_red <= (1<<17) && y_green <= (1<<17) && y_blue <= (1<<17))
-      {
-         /* The y values are chromaticities: Y/X+Y+Z, the weights for the gray
-          * transformation are simply the normalized Y values for red, green and
-          * blue scaled by 32768.
-          */
-         png_uint_32 w = y_red + y_green + y_blue;
+      png_XYZ XYZ;
+      png_xy xy;
 
-         png_ptr->rgb_to_gray_red_coeff   = (png_uint_16)(((png_uint_32)y_red *
-            32768)/w);
-         png_ptr->rgb_to_gray_green_coeff = (png_uint_16)(((png_uint_32)y_green
-            * 32768)/w);
-         png_ptr->rgb_to_gray_blue_coeff  = (png_uint_16)(((png_uint_32)y_blue *
-            32768)/w);
+      xy.redx = x_red;
+      xy.redy = y_red;
+      xy.greenx = x_green;
+      xy.greeny = y_green;
+      xy.bluex = x_blue;
+      xy.bluey = y_blue;
+      xy.whitex = x_white;
+      xy.whitey = y_white;
+
+      if (png_XYZ_from_xy_checked(png_ptr, &XYZ, xy))
+      {
+         /* The success case, because XYZ_from_xy normalises to a reference
+          * white Y of 1.0 we just need to scale the numbers.  This should
+          * always work just fine. It is an internal error if this overflows.
+          */
+         {
+            png_fixed_point r, g, b;
+            if (png_muldiv(&r, XYZ.redY, 32768, PNG_FP_1) &&
+               r >= 0 && r <= 32768 &&
+               png_muldiv(&g, XYZ.greenY, 32768, PNG_FP_1) &&
+               g >= 0 && g <= 32768 &&
+               png_muldiv(&b, XYZ.blueY, 32768, PNG_FP_1) &&
+               b >= 0 && b <= 32768 &&
+               r+g+b <= 32769)
+            {
+               /* We allow 0 coefficients here.  r+g+b may be 32769 if two or
+                * all of the coefficients were rounded up.  Handle this by
+                * reducing the *largest* coefficient by 1; this matches the
+                * approach used for the default coefficients in pngrtran.c
+                */
+               int add = 0;
+
+               if (r+g+b > 32768)
+                  add = -1;
+               else if (r+g+b < 32768)
+                  add = 1;
+
+               if (add != 0)
+               {
+                  if (g >= r && g >= b)
+                     g += add;
+                  else if (r >= g && r >= b)
+                     r += add;
+                  else
+                     b += add;
+               }
+
+               /* Check for an internal error. */
+               if (r+g+b != 32768)
+                  png_error(png_ptr,
+                     "internal error handling cHRM coefficients");
+
+               png_ptr->rgb_to_gray_red_coeff   = (png_uint_16)r;
+               png_ptr->rgb_to_gray_green_coeff = (png_uint_16)g;
+            }
+
+            /* This is a png_error at present even though it could be ignored -
+             * it should never happen, but it is important that if it does, the
+             * bug is fixed.
+             */
+            else
+               png_error(png_ptr, "internal error handling cHRM->XYZ");
+         }
       }
    }
 #endif
@@ -1135,6 +1188,47 @@ png_handle_sRGB(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       }
 #endif /* PNG_READ_cHRM_SUPPORTED */
 
+   /* This is recorded for use when handling the cHRM chunk above.  An sRGB
+    * chunk unconditionally overwrites the coefficients for grayscale conversion
+    * too.
+    */
+   png_ptr->is_sRGB = 1;
+
+#  ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+      /* Don't overwrite user supplied values: */
+      if (!png_ptr->rgb_to_gray_coefficients_set)
+      {
+         /* These numbers come from the sRGB specification (or, since one has to
+          * pay much money to get a copy, the wikipedia sRGB page) the
+          * chromaticity values quoted have been inverted to get the reverse
+          * transformation from RGB to XYZ and the 'Y' coefficients scaled by
+          * 32768 (then rounded).
+          *
+          * sRGB and ITU Rec-709 both truncate the values for the D65 white
+          * point to four digits and, even though it actually stores five
+          * digits, the PNG spec gives the truncated value.
+          *
+          * This means that when the chromaticities are converted back to XYZ
+          * end points we end up with (6968,23435,2366), which, as described in
+          * pngrtran.c, would overflow.  If the five digit precision and up is
+          * used we get, instead:
+          *
+          *    6968*R + 23435*G + 2365*B
+          *
+          * (Notice that this rounds the blue coefficient down, rather than the
+          * choice used in pngrtran.c which is to round the green one down.)
+          */
+         png_ptr->rgb_to_gray_red_coeff   =  6968; /* 0.212639005871510 */
+         png_ptr->rgb_to_gray_green_coeff = 23434; /* 0.715168678767756 */
+         /* png_ptr->rgb_to_gray_blue_coeff  =  2366; 0.072192315360734	*/
+
+         /* The following keeps the cHRM chunk from destroying the
+          * coefficients again in the event that it follows the sRGB chunk.
+          */
+         png_ptr->rgb_to_gray_coefficients_set = 1;
+      }
+#  endif
+
    png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr, intent);
 }
 #endif /* PNG_READ_sRGB_SUPPORTED */
@@ -2038,21 +2132,26 @@ png_handle_sCAL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    i = 1;
    state = 0;
 
-   if (png_ptr->chunkdata[1] == 45 /* negative width */ ||
-       !png_check_fp_number(png_ptr->chunkdata, slength, &state, &i) ||
+   if (!png_check_fp_number(png_ptr->chunkdata, slength, &state, &i) ||
        i >= slength || png_ptr->chunkdata[i++] != 0)
       png_warning(png_ptr, "Invalid sCAL chunk ignored: bad width format");
 
+   else if (!PNG_FP_IS_POSITIVE(state))
+      png_warning(png_ptr, "Invalid sCAL chunk ignored: non-positive width");
+
    else
    {
       png_size_t heighti = i;
 
       state = 0;
-      if (png_ptr->chunkdata[i] == 45 /* negative height */ ||
-          !png_check_fp_number(png_ptr->chunkdata, slength, &state, &i) ||
+      if (!png_check_fp_number(png_ptr->chunkdata, slength, &state, &i) ||
           i != slength)
          png_warning(png_ptr, "Invalid sCAL chunk ignored: bad height format");
 
+      else if (!PNG_FP_IS_POSITIVE(state))
+         png_warning(png_ptr,
+            "Invalid sCAL chunk ignored: non-positive height");
+
       else
          /* This is the (only) success case. */
          png_set_sCAL_s(png_ptr, info_ptr, png_ptr->chunkdata[0],
@@ -2679,7 +2778,7 @@ png_combine_row(png_structp png_ptr, png_bytep row, int mask)
 {
    png_debug(1, "in png_combine_row");
 
-   /* Added in 1.5.3: the row_info should match the information returned by any
+   /* Added in 1.5.4: the row_info should match the information returned by any
     * call to png_read_update_info at this point.  Do not continue if we got
     * this wrong.
     */

pngset.c

@@ -1,7 +1,7 @@
 
 /* pngset.c - storage of image information into info struct
  *
- * Last changed in libpng 1.5.1 [February 3, 2011]
+ * Last changed in libpng 1.5.4 [July 7, 2011]
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -64,6 +64,39 @@ png_set_cHRM_fixed(png_structp png_ptr, png_infop info_ptr,
    }
 }
 
+void PNGFAPI
+png_set_cHRM_XYZ_fixed(png_structp png_ptr, png_infop info_ptr,
+    png_fixed_point int_red_X, png_fixed_point int_red_Y,
+    png_fixed_point int_red_Z, png_fixed_point int_green_X,
+    png_fixed_point int_green_Y, png_fixed_point int_green_Z,
+    png_fixed_point int_blue_X, png_fixed_point int_blue_Y,
+    png_fixed_point int_blue_Z)
+{
+   png_XYZ XYZ;
+   png_xy xy;
+
+   png_debug1(1, "in %s storage function", "cHRM XYZ fixed");
+
+   if (png_ptr == NULL || info_ptr == NULL)
+      return;
+
+   XYZ.redX = int_red_X;
+   XYZ.redY = int_red_Y;
+   XYZ.redZ = int_red_Z;
+   XYZ.greenX = int_green_X;
+   XYZ.greenY = int_green_Y;
+   XYZ.greenZ = int_green_Z;
+   XYZ.blueX = int_blue_X;
+   XYZ.blueY = int_blue_Y;
+   XYZ.blueZ = int_blue_Z;
+
+   if (png_xy_from_XYZ(&xy, XYZ))
+      png_error(png_ptr, "XYZ values out of representable range");
+
+   png_set_cHRM_fixed(png_ptr, info_ptr, xy.whitex, xy.whitey, xy.redx, xy.redy,
+      xy.greenx, xy.greeny, xy.bluex, xy.bluey);
+}
+
 #  ifdef PNG_FLOATING_POINT_SUPPORTED
 void PNGAPI
 png_set_cHRM(png_structp png_ptr, png_infop info_ptr,
@@ -80,6 +113,23 @@ png_set_cHRM(png_structp png_ptr, png_infop info_ptr,
       png_fixed(png_ptr, blue_x, "cHRM Blue X"),
       png_fixed(png_ptr, blue_y, "cHRM Blue Y"));
 }
+
+void PNGAPI
+png_set_cHRM_XYZ(png_structp png_ptr, png_infop info_ptr, double red_X,
+    double red_Y, double red_Z, double green_X, double green_Y, double green_Z,
+    double blue_X, double blue_Y, double blue_Z)
+{
+   png_set_cHRM_XYZ_fixed(png_ptr, info_ptr,
+      png_fixed(png_ptr, red_X, "cHRM Red X"),
+      png_fixed(png_ptr, red_Y, "cHRM Red Y"),
+      png_fixed(png_ptr, red_Z, "cHRM Red Z"),
+      png_fixed(png_ptr, green_X, "cHRM Red X"),
+      png_fixed(png_ptr, green_Y, "cHRM Red Y"),
+      png_fixed(png_ptr, green_Z, "cHRM Red Z"),
+      png_fixed(png_ptr, blue_X, "cHRM Red X"),
+      png_fixed(png_ptr, blue_Y, "cHRM Red Y"),
+      png_fixed(png_ptr, blue_Z, "cHRM Red Z"));
+}
 #  endif /* PNG_FLOATING_POINT_SUPPORTED */
 
 #endif /* PNG_cHRM_SUPPORTED */
@@ -99,7 +149,7 @@ png_set_gAMA_fixed(png_structp png_ptr, png_infop info_ptr, png_fixed_point
     * possible for 1/gamma to overflow the limit of 21474 and this means the
     * gamma value must be at least 5/100000 and hence at most 20000.0.  For
     * safety the limits here are a little narrower.  The values are 0.00016 to
-    * 6250.0, which are truely ridiculous gammma values (and will produce
+    * 6250.0, which are truly ridiculous gammma values (and will produce
     * displays that are all black or all white.)
     */
    if (file_gamma < 16 || file_gamma > 625000000)

pngstruct.h

@@ -5,7 +5,7 @@
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
- * Last changed in libpng 1.5.4 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.4 [July 7, 2011]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -68,7 +68,7 @@ struct png_struct_def
    uInt zbuf_size;            /* size of zbuf (typically 65536) */
 #ifdef PNG_WRITE_SUPPORTED
 
-/* Added in 1.5.3: state to keep track of whether the zstream has been
+/* Added in 1.5.4: state to keep track of whether the zstream has been
  * initialized and if so whether it is for IDAT or some other chunk.
  */
 #define PNG_ZLIB_UNINITIALIZED 0
@@ -78,7 +78,7 @@ struct png_struct_def
 #define PNG_ZLIB_IN_USE        4 /* a flag value */
 
    png_uint_32 zlib_state;       /* State of zlib initialization */
-/* End of material added at libpng 1.5.3 */
+/* End of material added at libpng 1.5.4 */
 
    int zlib_level;            /* holds zlib compression level */
    int zlib_method;           /* holds zlib compression method */
@@ -86,7 +86,7 @@ struct png_struct_def
    int zlib_mem_level;        /* holds zlib compression memory level */
    int zlib_strategy;         /* holds zlib compression strategy */
 #endif
-/* Added at libpng 1.5.3 */
+/* Added at libpng 1.5.4 */
 #if defined(PNG_WRITE_COMPRESSED_TEXT_SUPPORTED) || \
     defined(PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED)
    int zlib_text_level;            /* holds zlib compression level */
@@ -95,7 +95,7 @@ struct png_struct_def
    int zlib_text_mem_level;        /* holds zlib compression memory level */
    int zlib_text_strategy;         /* holds zlib compression strategy */
 #endif
-/* End of material added at libpng 1.5.3 */
+/* End of material added at libpng 1.5.4 */
 
    png_uint_32 width;         /* width of image in pixels */
    png_uint_32 height;        /* height of image in pixels */
@@ -111,7 +111,7 @@ struct png_struct_def
    png_bytep avg_row;         /* buffer to save "avg" row when filtering */
    png_bytep paeth_row;       /* buffer to save "Paeth" row when filtering */
    png_row_info row_info;     /* used for transformation routines */
-   png_size_t info_rowbytes;  /* Added in 1.5.3: cache of updated row bytes */
+   png_size_t info_rowbytes;  /* Added in 1.5.4: cache of updated row bytes */
 
    png_uint_32 idat_size;     /* current IDAT size for read */
    png_uint_32 crc;           /* current chunk CRC value */
@@ -255,13 +255,20 @@ struct png_struct_def
    png_bytep chunk_list;
 #endif
 
+#ifdef PNG_READ_sRGB_SUPPORTED
+   /* Added in 1.5.5 to record an sRGB chunk in the png. */
+   png_byte is_sRGB;
+#endif
+
 /* New members added in libpng-1.0.3 */
 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
    png_byte rgb_to_gray_status;
+   /* Added in libpng 1.5.5 to record setting of coefficients: */
+   png_byte rgb_to_gray_coefficients_set;
    /* These were changed from png_byte in libpng-1.0.6 */
    png_uint_16 rgb_to_gray_red_coeff;
    png_uint_16 rgb_to_gray_green_coeff;
-   png_uint_16 rgb_to_gray_blue_coeff;
+   /* deleted in 1.5.5: rgb_to_gray_blue_coeff; */
 #endif
 
 /* New member added in libpng-1.0.4 (renamed in 1.0.9) */

pngtest.c

@@ -1,7 +1,7 @@
 
 /* pngtest.c - a simple test program to test libpng
  *
- * Last changed in libpng 1.5.4 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.4 [July 7, 2011]
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -918,7 +918,7 @@ test_one_file(PNG_CONST char *inname, PNG_CONST char *outname)
 #ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
    /* Normally one would use Z_DEFAULT_STRATEGY for text compression.
     * This is here just to make pngtest replicate the results from libpng
-    * versions prior to 1.5.3, and to test this new API.
+    * versions prior to 1.5.4, and to test this new API.
     */
    png_set_text_compression_strategy(write_ptr, Z_FILTERED);
 #endif
@@ -1794,4 +1794,4 @@ main(int argc, char *argv[])
 }
 
 /* Generate a compiler error if there is an old png.h in the search path. */
-typedef png_libpng_version_1_5_4beta02 Your_png_h_is_not_version_1_5_4beta02;
+typedef png_libpng_version_1_5_5beta06 Your_png_h_is_not_version_1_5_5beta06;

pngtrans.c

@@ -1,7 +1,7 @@
 
 /* pngtrans.c - transforms the data in a row (used by both readers and writers)
  *
- * Last changed in libpng 1.5.4 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.4 [July 7, 2011]
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)

pngwrite.c

@@ -1,7 +1,7 @@
 
 /* pngwrite.c - general routines to write a PNG file
  *
- * Last changed in libpng 1.5.4 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.4 [July 7, 2011]
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -1458,7 +1458,7 @@ png_set_compression_method(png_structp png_ptr, int method)
    png_ptr->zlib_method = method;
 }
 
-/* The following were added to libpng-1.5.3 */
+/* The following were added to libpng-1.5.4 */
 #ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
 void PNGAPI
 png_set_text_compression_level(png_structp png_ptr, int level)
@@ -1539,7 +1539,7 @@ png_set_text_compression_method(png_structp png_ptr, int method)
    png_ptr->zlib_text_method = method;
 }
 #endif /* PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED */
-/* end of API added to libpng-1.5.3 */
+/* end of API added to libpng-1.5.4 */
 
 void PNGAPI
 png_set_write_status_fn(png_structp png_ptr, png_write_status_ptr write_row_fn)

pngwtran.c

@@ -1,7 +1,7 @@
 
 /* pngwtran.c - transforms the data in a row for PNG writers
  *
- * Last changed in libpng 1.5.4 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.4 [July 7, 2011]
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)

pngwutil.c

@@ -1,7 +1,7 @@
 
 /* pngwutil.c - utilities to write a PNG file
  *
- * Last changed in libpng 1.5.4 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.4 [July 7, 2011]
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -1017,7 +1017,7 @@ png_write_IDAT(png_structp png_ptr, png_bytep data, png_size_t length)
    png_write_chunk(png_ptr, png_IDAT, data, length);
    png_ptr->mode |= PNG_HAVE_IDAT;
 
-   /* Prior to 1.5.3 this code was replicated in every caller (except at the
+   /* Prior to 1.5.4 this code was replicated in every caller (except at the
     * end, where it isn't technically necessary).  Since this function has
     * flushed the data we can safely reset the zlib output buffer here.
     */

projects/vstudio/libpng/libpng.vcxproj

@@ -118,7 +118,7 @@
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
-      <PreprocessorDefinitions>WIN32;_DEBUG;_WINDOWS;_USRDLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;_DEBUG;_WINDOWS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <IntrinsicFunctions>true</IntrinsicFunctions>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <FloatingPointExceptions>false</FloatingPointExceptions>
@@ -175,7 +175,7 @@
       <RuntimeLibrary>MultiThreaded</RuntimeLibrary>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <PreprocessorDefinitions>WIN32;NDEBUG;_WINDOWS;_USRDLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;NDEBUG;_WINDOWS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <FloatingPointExceptions>false</FloatingPointExceptions>
       <TreatWChar_tAsBuiltInType>false</TreatWChar_tAsBuiltInType>
       <PrecompiledHeaderFile>pngpriv.h</PrecompiledHeaderFile>

projects/vstudio/pngvalid/pngvalid.vcxproj

@@ -81,7 +81,7 @@
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
       <BasicRuntimeChecks>EnableFastChecks</BasicRuntimeChecks>
-      <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;PNG_USE_DLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
       <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>
@@ -146,7 +146,7 @@
       <Optimization>Full</Optimization>
       <FunctionLevelLinking>false</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;PNG_USE_DLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>$(ZLibSrcDir);..\..\..\scripts;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
       <DisableSpecificWarnings>4996;4127</DisableSpecificWarnings>
       <CompileAsManaged>false</CompileAsManaged>

projects/vstudio/readme.txt

@@ -1,7 +1,7 @@
 
 VisualStudio instructions
 
-libpng version 1.5.4beta02 - June 14, 2011
+libpng version 1.5.5beta06 - August 25, 2011
 
 Copyright (c) 1998-2010 Glenn Randers-Pehrson
 

projects/vstudio/zlib.props

@@ -2,7 +2,7 @@
 <!--
  * zlib.props - location of zlib source
  *
- * libpng version 1.5.4beta02 - June 14, 2011
+ * libpng version 1.5.5beta06 - August 25, 2011
  *
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  *

projects/vstudio/zlib/zlib.vcxproj

@@ -84,7 +84,7 @@
   </PropertyGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug Library|Win32'">
     <ClCompile>
-      <PreprocessorDefinitions>WIN32;_DEBUG;_WINDOWS;_USRDLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;_DEBUG;_WINDOWS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <RuntimeLibrary>MultiThreadedDebug</RuntimeLibrary>
       <WarningLevel>TurnOffAllWarnings</WarningLevel>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
@@ -99,7 +99,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
     <ClCompile>
-      <PreprocessorDefinitions>WIN32;_DEBUG;_WINDOWS;_USRDLL;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;_DEBUG;_WINDOWS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <WarningLevel>TurnOffAllWarnings</WarningLevel>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
       <Optimization>Disabled</Optimization>
@@ -156,7 +156,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
     <ClCompile>
-      <PreprocessorDefinitions>WIN32;NDEBUG;_WINDOWS;_USRDLL;DEBUGZLIB_EXPORTS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;NDEBUG;_WINDOWS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <WarningLevel>Level3</WarningLevel>
       <DebugInformationFormat>ProgramDatabase</DebugInformationFormat>
     </ClCompile>

scripts/README.txt

@@ -1,9 +1,9 @@
 
-Makefiles for  libpng version 1.5.4beta02 - June 14, 2011
+Makefiles for  libpng version 1.5.5beta06 - August 25, 2011
 
 pnglibconf.h.prebuilt       =>  Stores configuration settings
  makefile.linux    =>  Linux/ELF makefile
-                       (gcc, creates libpng15.so.15.1.5.4beta02)
+                       (gcc, creates libpng15.so.15.1.5.5beta06)
  makefile.gcc      =>  Generic makefile (gcc, creates static libpng.a)
  makefile.knr      =>  Archaic UNIX Makefile that converts files with
                        ansi2knr (Requires ansi2knr.c from
@@ -20,7 +20,7 @@ pnglibconf.h.prebuilt       =>  Stores configuration settings
  makefile.dec      =>  DEC Alpha UNIX makefile
  makefile.dj2      =>  DJGPP 2 makefile
  makefile.elf      =>  Linux/ELF makefile symbol versioning,
-                       (gcc, creates libpng15.so.15.1.5.4beta02)
+                       (gcc, creates libpng15.so.15.1.5.5beta06)
  makefile.freebsd  =>  FreeBSD makefile
  makefile.gcc      =>  Generic gcc makefile
  makefile.hpgcc    =>  HPUX makefile using gcc
@@ -35,12 +35,12 @@ pnglibconf.h.prebuilt       =>  Stores configuration settings
  makefile.os2      =>  OS/2 Makefile (gcc and emx, requires libpng.def)
  makefile.sco      =>  For SCO OSr5  ELF and Unixware 7 with Native cc
  makefile.sggcc    =>  Silicon Graphics (gcc,
-                       creates libpng15.so.15.1.5.4beta02)
+                       creates libpng15.so.15.1.5.5beta06)
  makefile.sgi      =>  Silicon Graphics IRIX makefile (cc, creates static lib)
  makefile.solaris  =>  Solaris 2.X makefile (gcc,
-                       creates libpng15.so.15.1.5.4beta02)
+                       creates libpng15.so.15.1.5.5beta06)
  makefile.so9      =>  Solaris 9 makefile (gcc,
-                       creates libpng15.so.15.1.5.4beta02)
+                       creates libpng15.so.15.1.5.5beta06)
  makefile.std      =>  Generic UNIX makefile (cc, creates static libpng.a)
  makefile.sunos    =>  Sun makefile
  makefile.32sunu   =>  Sun Ultra 32-bit makefile
@@ -57,7 +57,7 @@ Other supporting scripts:
  libpng-config-body.in => used by several makefiles to create libpng-config
  libpng-config-head.in => used by several makefiles to create libpng-config
  libpng.pc.in      =>  Used by several makefiles to create libpng.pc
- pngwin.rc         =>  Used by the visualc6 and visualc71 projects.
+ pngwin.rc         =>  Used by the visualc71 project.
  pngwin.def        =>  Used by makefile.os2
  pngwin.dfn        =>  Used to maintain pngwin.def
  SCOPTIONS.ppc     =>  Used with smakefile.ppc

scripts/libpng-config-head.in

@@ -11,7 +11,7 @@
 
 # Modeled after libxml-config.
 
-version=1.5.4beta02
+version=1.5.5beta06
 prefix=""
 libdir=""
 libs=""

scripts/libpng.pc.in

@@ -5,6 +5,6 @@ includedir=@includedir@/libpng15
 
 Name: libpng
 Description: Loads and saves PNG files
-Version: 1.5.4beta02
+Version: 1.5.5beta06
 Libs: -L${libdir} -lpng15
 Cflags: -I${includedir}

scripts/makefile.cegcc

@@ -23,7 +23,7 @@
 
 VERMAJ = 1
 VERMIN = 5
-VERMIC = 4
+VERMIC = 5
 VER = $(VERMAJ).$(VERMIN).$(VERMIC)
 NAME = libpng
 PACKAGE = $(NAME)-$(VER)

scripts/makefile.linux

@@ -10,7 +10,7 @@
 # Library name:
 LIBNAME = libpng15
 PNGMAJ = 15
-RELEASE = 4
+RELEASE = 5
 
 # Shared library names:
 LIBSO=$(LIBNAME).so

scripts/makefile.ne12bsd

@@ -17,7 +17,7 @@ INCSDIR=${LOCALBASE}/include/libpng15
 
 LIB=	png15
 SHLIB_MAJOR=	0
-SHLIB_MINOR=	1.5.4beta02
+SHLIB_MINOR=	1.5.5beta06
 SRCS=	png.c pngset.c pngget.c pngrutil.c pngtrans.c pngwutil.c \
 	pngread.c pngrio.c pngwio.c pngwrite.c pngrtran.c \
 	pngwtran.c pngmem.c pngerror.c pngpread.c

scripts/makefile.netbsd

@@ -17,7 +17,7 @@ INCSDIR=${LOCALBASE}/include
 
 LIB=	png
 SHLIB_MAJOR=	15
-SHLIB_MINOR=	1.5.4beta02
+SHLIB_MINOR=	1.5.5beta06
 SRCS=	png.c pngset.c pngget.c pngrutil.c pngtrans.c pngwutil.c \
 	pngread.c pngrio.c pngwio.c pngwrite.c pngrtran.c \
 	pngwtran.c pngmem.c pngerror.c pngpread.c

scripts/makefile.openbsd

@@ -11,7 +11,7 @@ LIBDIR=	${PREFIX}/lib
 MANDIR= ${PREFIX}/man/cat
 
 SHLIB_MAJOR=	15
-SHLIB_MINOR=	1.5.4beta02
+SHLIB_MINOR=	1.5.5beta06
 
 LIB=	png
 SRCS=	png.c pngerror.c pngget.c pngmem.c pngpread.c \

scripts/pnglibconf.dfa

@@ -6,7 +6,7 @@
 #
 com pnglibconf.h - library build configuration
 com
-com libpng version 1.5.3 -  (PENDING RELEASE)
+com libpng version 1.5.3 -  July 7, 2011
 com
 com Copyright (c) 1998-2011 Glenn Randers-Pehrson
 com
@@ -294,7 +294,9 @@ option READ enables READ_INTERLACING
 # Disabling READ_16BIT does not disable reading 16-bit PNG files, but it
 # forces them to be chopped down to 8-bit, and disables any 16-bit
 # processing after that has happened.  You need to be sure to enable
-# READ_16_TO_8 when you disable READ_16BIT for this to work properly.
+# READ_SCALE_16_TO_8 or READ_STRIP_16_TO_8 when you disable READ_16BIT for
+# this to work properly.  You should disable the other option if you need to
+# ensure a particular convertion (otherwise the app can chose.)
 
 option READ_16BIT requires READ enables 16BIT
 
@@ -312,7 +314,8 @@ option READ_SWAP requires READ_TRANSFORMS READ_16BIT
 option READ_PACKSWAP requires READ_TRANSFORMS
 option READ_INVERT requires READ_TRANSFORMS
 option READ_BACKGROUND requires READ_TRANSFORMS enables READ_STRIP_ALPHA
-option READ_16_TO_8 requires READ_TRANSFORMS
+option READ_STRIP_16_TO_8 requires READ_TRANSFORMS
+option READ_SCALE_16_TO_8 requires READ_TRANSFORMS
 option READ_FILLER requires READ_TRANSFORMS
 option READ_GAMMA requires READ_TRANSFORMS enables READ_gAMA
 option READ_GRAY_TO_RGB requires READ_TRANSFORMS
@@ -552,8 +555,6 @@ option SAVE_INT_32 requires WRITE
 
 # added at libpng-1.5.4
 
-option READ_CHOP_16_TO_8 requires READ_16_TO_8
-
 option WRITE_OPTIMIZE_CMF requires WRITE
 
 option READ_COMPRESSED_TEXT disabled

scripts/pnglibconf.h.prebuilt

@@ -3,7 +3,7 @@
 
 /* pnglibconf.h - library build configuration */
 
-/* libpng version 1.5.0 - last changed on February 11, 2011 */
+/* libpng version 1.5.4 - last changed on June 22, 2011 */
 
 /* Copyright (c) 1998-2011 Glenn Randers-Pehrson */
 
@@ -49,6 +49,7 @@
 #define PNG_CONSOLE_IO_SUPPORTED
 #define PNG_CONVERT_tIME_SUPPORTED
 #define PNG_EASY_ACCESS_SUPPORTED
+/*#undef PNG_ERROR_NUMBERS_SUPPORTED*/
 #define PNG_ERROR_TEXT_SUPPORTED
 #define PNG_FIXED_POINT_SUPPORTED
 #define PNG_FLOATING_ARITHMETIC_SUPPORTED
@@ -68,16 +69,14 @@
 #define PNG_POINTER_INDEXING_SUPPORTED
 #define PNG_PROGRESSIVE_READ_SUPPORTED
 #define PNG_READ_16BIT_SUPPORTED
-#define PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
-#define PNG_READ_16_TO_8_SUPPORTED
 #define PNG_READ_ALPHA_MODE_SUPPORTED
 #define PNG_READ_ANCILLARY_CHUNKS_SUPPORTED
 #define PNG_READ_BACKGROUND_SUPPORTED
 #define PNG_READ_BGR_SUPPORTED
 #define PNG_READ_bKGD_SUPPORTED
 #define PNG_READ_cHRM_SUPPORTED
-#define PNG_READ_CHOP_16_TO_8_SUPPORTED
 #define PNG_READ_COMPOSITE_NODIV_SUPPORTED
+#define PNG_READ_COMPRESSED_TEXT_SUPPORTED
 #define PNG_READ_EXPAND_16_SUPPORTED
 #define PNG_READ_EXPAND_SUPPORTED
 #define PNG_READ_FILLER_SUPPORTED
@@ -100,10 +99,12 @@
 #define PNG_READ_QUANTIZE_SUPPORTED
 #define PNG_READ_RGB_TO_GRAY_SUPPORTED
 #define PNG_READ_sBIT_SUPPORTED
+#define PNG_READ_SCALE_16_TO_8_SUPPORTED
 #define PNG_READ_sCAL_SUPPORTED
 #define PNG_READ_SHIFT_SUPPORTED
 #define PNG_READ_sPLT_SUPPORTED
 #define PNG_READ_sRGB_SUPPORTED
+#define PNG_READ_STRIP_16_TO_8_SUPPORTED
 #define PNG_READ_STRIP_ALPHA_SUPPORTED
 #define PNG_READ_SUPPORTED
 #define PNG_READ_SWAP_ALPHA_SUPPORTED
@@ -117,7 +118,6 @@
 #define PNG_READ_USER_CHUNKS_SUPPORTED
 #define PNG_READ_USER_TRANSFORM_SUPPORTED
 #define PNG_READ_zTXt_SUPPORTED
-#define PNG_READ_COMPRESSED_TEXT_SUPPORTED
 #define PNG_SAVE_INT_32_SUPPORTED
 #define PNG_sBIT_SUPPORTED
 #define PNG_sCAL_SUPPORTED
@@ -146,6 +146,8 @@
 #define PNG_WRITE_BGR_SUPPORTED
 #define PNG_WRITE_bKGD_SUPPORTED
 #define PNG_WRITE_cHRM_SUPPORTED
+#define PNG_WRITE_COMPRESSED_TEXT_SUPPORTED
+#define PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
 #define PNG_WRITE_FILLER_SUPPORTED
 #define PNG_WRITE_FILTER_SUPPORTED
 #define PNG_WRITE_FLUSH_SUPPORTED
@@ -156,7 +158,6 @@
 #define PNG_WRITE_INT_FUNCTIONS_SUPPORTED
 #define PNG_WRITE_INVERT_ALPHA_SUPPORTED
 #define PNG_WRITE_INVERT_SUPPORTED
-#define PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
 #define PNG_WRITE_iTXt_SUPPORTED
 #define PNG_WRITE_oFFs_SUPPORTED
 #define PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
@@ -182,7 +183,5 @@
 #define PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
 #define PNG_WRITE_zTXt_SUPPORTED
 #define PNG_zTXt_SUPPORTED
-#define PNG_WRITE_COMPRESSED_TEXT_SUPPORTED
-/*#undef PNG_ERROR_NUMBERS_SUPPORTED*/
 /* end of options */
 #endif /* PNGLCONF_H */

scripts/symbols.def

@@ -5,7 +5,7 @@
 LIBRARY
 
 EXPORTS
-;Version 1.5.4beta02
+;Version 1.5.5beta06
  png_access_version_number @1
  png_set_sig_bytes @2
  png_sig_cmp @3
@@ -234,4 +234,8 @@ EXPORTS
  png_set_text_compression_method @226
  png_set_alpha_mode @227
  png_set_alpha_mode_fixed @228
- png_set_chop_16 @229
+ png_set_scale_16 @229
+ png_get_cHRM_XYZ @230
+ png_get_cHRM_XYZ_fixed @231
+ png_set_cHRM_XYZ @232
+ png_set_cHRM_XYZ_fixed @233