[master] Imported from libpng-1.6.18.tar

[master] Imported from libpng-1.6.17.tar
[master] Imported from libpng-1.6.16.tar
2025-07-10 18:04:09 +02:00 · 2015-07-22 22:41:05 -05:00 · 2015-03-26 08:11:22 -05:00 · 2015-01-15 12:47:40 -05:00 · 2014-11-20 10:23:30 -06:00 · 2014-10-22 19:33:27 -05:00
49 changed files with 1119 additions and 1698 deletions
--- a/66
+++ b/66
@@ -1,31 +1,28 @@
-Libpng 1.6.18beta04 - May 20, 2015
+Libpng 1.6.18 - July 23, 2015

-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.
+This is a public release of libpng, intended for use in production codes.

 Files available for download:

 Source files with LF line endings (for Unix/Linux) and with a
 "configure" script

-   1.6.18beta04.tar.xz (LZMA-compressed, recommended)
-   1.6.18beta04.tar.gz
+   libpng-1.6.18.tar.xz (LZMA-compressed, recommended)
+   libpng-1.6.18.tar.gz

 Source files with CRLF line endings (for Windows), without the
 "configure" script

-   lp1618b04.7z  (LZMA-compressed, recommended)
-   lp1618b04.zip
+   lpng1618.7z  (LZMA-compressed, recommended)
+   lpng1618.zip

 Other information:

-   1.6.18beta04-README.txt
-   1.6.18beta04-LICENSE.txt
-   libpng-1.6.18beta04-*.asc (armored detached GPG signatures)
+   libpng-1.6.18-README.txt
+   libpng-1.6.18-LICENSE.txt
+   libpng-1.6.18-*.asc (armored detached GPG signatures)

 Changes since the last public release (1.6.17):
-
-Version 1.6.18beta01 [April 1, 2015]
  Removed PNG_SET_CHUNK_[CACHE|MALLOC]_LIMIT_SUPPORTED macros.  They
    have been combined with PNG_SET_USER_LIMITS_SUPPORTED (resolves
    bug report by Andrew Church).
@@ -33,25 +30,56 @@ Version 1.6.18beta01 [April 1, 2015]
    fixes some arithmetic errors that caused some tests to fail on
    some 32-bit platforms (Bug reports by Peter Breitenlohner [i686]
    and Petr Gajdos [i586]).
-
-Version 1.6.18beta02 [April 26, 2015]
  Suppressed some warnings from the Borland C++ 5.5.1/5.82 compiler
    (Bug report by Viktor Szaka'ts).
-
-Version 1.6.18beta03 [May 6, 2015]
  Replaced "unexpected" with an integer (0xabadca11) in pngset.c
    where a long was expected, to avoid a compiler warning when PNG_DEBUG > 1.
  Added contrib/examples/simpleover.c, to demonstrate how to handle
    alpha compositing of multiple images, using the "simplified API"
    and an example PNG generation tool, contrib/examples/genpng.c
    (John Bowler).
-
-Version 1.6.18beta04 [May 20, 2015]
  PNG_RELEASE_BUILD replaces tests where the code depended on the build base
    type and can be defined on the command line, allowing testing in beta
    builds (John Bowler).
  Avoid Coverity issue 80858 (REVERSE NULL) in pngtest.c
-  Avoid a harmless potential integer overflow in png_XYZ_from_xy().
+  Avoid a harmless potential integer overflow in png_XYZ_from_xy() (Bug
+    report from Christopher Ferris).
+  Backport filter selection code from libpng-1.7.0beta51, to combine
+    sub_row, up_row, avg_row, and paeth_row into try_row and tst_row.
+  Changed png_voidcast(), etc., to voidcast(), etc., in contrib/tools/pngfix.c
+    to avoid confusion with the libpng private macros.
+  Fixed old cut&paste bug in the weighted filter selection code in
+    pngwutil.c, introduced in libpng-0.95, March 1997.
+  Removed WRITE_WEIGHTED_FILTERED code, to save a few kbytes of the
+    compiled library size. It never worked properly and as far as we can
+    tell, no one uses it. The png_set_filter_heuristics() and
+    png_set_filter_heuristics_fixed() APIs are retained but deprecated
+    and do nothing.
+  Quieted some Coverity issues in pngfix.c, png-fix-itxt.c, pngvalid.c,
+    pngstest.c, and pngimage.c. Most seem harmless, but png-fix-itxt
+    would only work with iTXt chunks with length 255 or less.
+  Removed non-working progressive reader 'skip' function. This
+    function has apparently never been used. It was implemented
+    to support back-door modification of png_struct in libpng-1.4.x
+    but (because it does nothing and cannot do anything) was apparently
+    never tested (John Bowler).
+  Fixed cexcept.h in which GCC 5 now reports that one of the auto
+    variables in the Try macro needs to be volatile to prevent value
+    being lost over the setjmp (John Bowler).
+  Added #ifdef's to contrib/examples programs so people don't try
+    to compile them without the minimum required support enabled
+    (suggested by Flavio Medeiros).
+  Eliminated the final two Coverity defects (insecure temporary file
+    handling in contrib/libtests/pngstest.c; possible overflow of
+    unsigned char in contrib/tools/png-fix-itxt.c). To use the "secure"
+    file handling, define PNG_USE_MKSTEMP, otherwise "tmpfile()" will
+    be used.
+  Removed some unused WEIGHTED_FILTER macros from pngstruct.h
+  Replaced arbitrary use of 'extern' with #define PNG_LINKAGE_*.  To
+    preserve API compatibility, the new defines all default to "extern"
+    (requested by Jan Nijtmans).
+  Belatedly added Mans Rullgard and James Yu to the list of Contributing
+    Authors.

 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
--- a/103
+++ b/103
@@ -95,7 +95,7 @@ Version 0.88 [January, 1996]
  cleaned up documentation
  added callbacks for read/write and warning/error functions

-Version 0.89 [July, 1996]
+Version 0.89 [June 5, 1996]
  Added new initialization API to make libpng work better with shared libs
    we now have png_create_read_struct(), png_create_write_struct(),
    png_create_info_struct(), png_destroy_read_struct(), and
@@ -122,6 +122,9 @@ Version 0.89 [July, 1996]
  New pngtest image also has interlacing and zTXt
  Updated documentation to reflect new API

+Version 0.89c [June 17, 1996]
+  Bug fixes.
+
 Version 0.90 [January, 1997]
  Made CRC errors/warnings on critical and ancillary chunks configurable
  libpng will use the zlib CRC routines by (compile-time) default
@@ -162,7 +165,7 @@ Version 0.95 [March, 1997]
  Added new pCAL chunk read/write support
  Added experimental filter selection weighting (Greg Roelofs)
  Removed old png_set_rgbx() and png_set_xrgb() functions that have been
-     obsolete for about 2 years now (use png_set_filler() instead)
+    obsolete for about 2 years now (use png_set_filler() instead)
  Added macros to read 16- and 32-bit ints directly from buffer, to be
    used only on those systems that support it (namely PowerPC and 680x0)
    With some testing, this may become the default for MACOS/PPC systems.
@@ -444,7 +447,7 @@ Version 1.0.3 [January 14, 1999]

 Version 1.0.3a [August 12, 1999]
  Added check for PNG_READ_INTERLACE_SUPPORTED in pngread.c; issue a warning
-     if an attempt is made to read an interlaced image when it's not supported.
+    if an attempt is made to read an interlaced image when it's not supported.
  Added check if png_ptr->trans is defined before freeing it in pngread.c
  Modified the Y2K statement to include versions back to version 0.71
  Fixed a bug in the check for valid IHDR bit_depth/color_types in pngrutil.c
@@ -452,7 +455,7 @@ Version 1.0.3a [August 12, 1999]
  Replaced leading blanks with tab characters in makefile.hux
  Changed "dworkin.wustl.edu" to "ccrc.wustl.edu" in various documents.
  Changed (float)red and (float)green to (double)red, (double)green
-     in png_set_rgb_to_gray() to avoid "promotion" problems in AIX.
+    in png_set_rgb_to_gray() to avoid "promotion" problems in AIX.
  Fixed a bug in pngconf.h that omitted <stdio.h> when PNG_DEBUG==0 (K Bracey).
  Reformatted libpng.3 and libpngpf.3 with proper fonts (script by J. vanZandt).
  Updated documentation to refer to the PNG-1.2 specification.
@@ -495,7 +498,7 @@ Version 1.0.3d [September 4, 1999]
  Added new png_expand functions to scripts/pngdef.pas and pngos2.def
  Added a demo read_user_transform_fn that examines the row filters in pngtest.c

-Version 1.0.4 [September 24, 1999]
+Version 1.0.4 [September 24, 1999, not distributed publicly]
  Define PNG_ALWAYS_EXTERN in pngconf.h if __STDC__ is defined
  Delete #define PNG_INTERNAL and include "png.h" from pngasmrd.h
  Made several minor corrections to pngtest.c
@@ -522,6 +525,7 @@ Version 1.0.4c [October 1, 1999]
  Added a "png_check_version" function in png.c and pngtest.c that will generate
    a helpful compiler error if an old png.h is found in the search path.
  Changed type of png_user_transform_depth|channels from int to png_byte.
+  Added "Libpng is OSI Certified Open Source Software" statement to png.h

 Version 1.0.4d [October 6, 1999]
  Changed 0.45 to 0.45455 in png_set_sRGB()
@@ -908,7 +912,7 @@ Version 1.0.7 [July 1, 2000]
 Version 1.0.8beta1 [July 8, 2000]
  Added png_free(png_ptr, key) two places in pngpread.c to stop memory leaks.
  Changed PNG_NO_STDIO to PNG_NO_CONSOLE_IO, several places in pngrutil.c and
-     pngwutil.c.
+    pngwutil.c.
  Changed PNG_EXPORT_VAR to use PNG_IMPEXP, in pngconf.h.
  Removed unused "#include <assert.h>" from png.c
  Added WindowsCE support.
@@ -916,12 +920,12 @@ Version 1.0.8beta1 [July 8, 2000]

 Version 1.0.8beta2 [July 10, 2000]
  Added project files to the wince directory and made further revisions
-     of pngtest.c, pngrio.c, and pngwio.c in support of WindowsCE.
+    of pngtest.c, pngrio.c, and pngwio.c in support of WindowsCE.

 Version 1.0.8beta3 [July 11, 2000]
  Only set the PNG_FLAG_FREE_TRNS or PNG_FREE_TRNS flag in png_handle_tRNS()
-     for indexed-color input files to avoid potential double-freeing trans array
-     under some unusual conditions; problem was introduced in version 1.0.6f.
+    for indexed-color input files to avoid potential double-freeing trans array
+    under some unusual conditions; problem was introduced in version 1.0.6f.
  Further revisions to pngtest.c and files in the wince subdirectory.

 Version 1.0.8beta4 [July 14, 2000]
@@ -1093,16 +1097,16 @@ Version 1.2.0beta3 [May 17, 2001]

 Version 1.2.0beta4 [June 23, 2001]
  Check for missing profile length field in iCCP chunk and free chunk_data
-     in case of truncated iCCP chunk.
+    in case of truncated iCCP chunk.
  Bumped shared-library number to 3 in makefile.sgi and makefile.sggcc
  Bumped dll-number from 2 to 3 in makefile.cygwin
  Revised contrib/gregbook/rpng*-x.c to avoid a memory leak and to exit cleanly
-     if user attempts to run it on an 8-bit display.
+    if user attempts to run it on an 8-bit display.
  Updated contrib/gregbook
  Use png_malloc instead of png_zalloc to allocate palette in pngset.c
  Updated makefile.ibmc
  Added some typecasts to eliminate gcc 3.0 warnings.  Changed prototypes
-     of png_write_oFFS width and height from png_uint_32 to png_int_32.
+    of png_write_oFFS width and height from png_uint_32 to png_int_32.
  Updated example.c
  Revised prototypes for png_debug_malloc and png_debug_free in pngtest.c

@@ -1110,9 +1114,9 @@ Version 1.2.0beta5 [August 8, 2001]
  Revised contrib/gregbook
  Revised makefile.gcmmx
  Revised pnggccrd.c to conditionally compile some thread-unsafe code only
-     when PNG_THREAD_UNSAFE_OK is defined.
+    when PNG_THREAD_UNSAFE_OK is defined.
  Added tests to prevent pngwutil.c from writing a bKGD or tRNS chunk with
-     value exceeding 2^bit_depth-1
+    value exceeding 2^bit_depth-1
  Revised makefile.sgi and makefile.sggcc
  Replaced calls to fprintf(stderr,...) with png_warning() in pnggccrd.c
  Removed restriction that do_invert_mono only operate on 1-bit opaque files
@@ -1498,7 +1502,7 @@ Version 1.0.16rc4 and 1.2.6rc4 [August 10, 2004]

 Version 1.0.16rc5 and 1.2.6rc5 [August 10, 2004]
  Moved  "PNG_HANDLE_CHUNK_*" macros out of PNG_ASSEMBLER_CODE_SUPPORTED
-     section of png.h where they were inadvertently placed in version rc3.
+    section of png.h where they were inadvertently placed in version rc3.

 Version 1.2.6 and 1.0.16 [August 15, 2004]
  Revised pngtest so memory allocation testing is only done when PNG_DEBUG==1.
@@ -2330,7 +2334,7 @@ Version 1.4.0beta63 [June 15, 2009]
 Version 1.4.0beta64 [June 24, 2009]
  Eliminated PNG_LEGACY_SUPPORTED code.
  Moved the various unknown chunk macro definitions outside of the
-     PNG_READ|WRITE_ANCILLARY_CHUNK_SUPPORTED blocks.
+    PNG_READ|WRITE_ANCILLARY_CHUNK_SUPPORTED blocks.

 Version 1.4.0beta65 [June 26, 2009]
  Added a reference to the libpng license in each file.
@@ -4530,7 +4534,7 @@ Version 1.6.3beta03 [April 30, 2013]
  Expanded manual paragraph about writing private chunks, particularly
    the need to call png_set_keep_unknown_chunks() when writing them.
  Avoid dereferencing NULL pointer possibly returned from
-     png_create_write_struct() (Andrew Church).
+    png_create_write_struct() (Andrew Church).

 Version 1.6.3beta05 [May 9, 2013]
  Calculate our own zlib windowBits when decoding rather than trusting the
@@ -5236,7 +5240,70 @@ Version 1.6.18beta04 [May 20, 2015]
    type and can be defined on the command line, allowing testing in beta
    builds (John Bowler).
  Avoid Coverity issue 80858 (REVERSE NULL) in pngtest.c PNG_DEBUG builds.
-  Avoid a harmless potential integer overflow in png_XYZ_from_xy().
+  Avoid a harmless potential integer overflow in png_XYZ_from_xy() (Bug
+    report from Christopher Ferris).
+
+Version 1.6.18beta05 [May 31, 2015]
+  Backport filter selection code from libpng-1.7.0beta51, to combine
+    sub_row, up_row, avg_row, and paeth_row into try_row and tst_row.
+  Changed png_voidcast(), etc., to voidcast(), etc., in contrib/tools/pngfix.c
+    to avoid confusion with the libpng private macros.
+  Fixed old cut&paste bug in the weighted filter selection code in
+    pngwutil.c, introduced in libpng-0.95, March 1997.
+
+Version 1.6.18beta06 [June 1, 2015]
+  Removed WRITE_WEIGHTED_FILTERED code, to save a few kbytes of the
+    compiled library size. It never worked properly and as far as we can
+    tell, no one uses it. The png_set_filter_heuristics() and
+    png_set_filter_heuristics_fixed() APIs are retained but deprecated
+    and do nothing.
+
+Version 1.6.18beta07 [June 6, 2015]
+  Removed non-working progressive reader 'skip' function. This
+    function has apparently never been used. It was implemented
+    to support back-door modification of png_struct in libpng-1.4.x
+    but (because it does nothing and cannot do anything) was apparently
+    never tested (John Bowler).
+  Fixed cexcept.h in which GCC 5 now reports that one of the auto
+    variables in the Try macro needs to be volatile to prevent value
+    being lost over the setjmp (John Bowler).
+  Fixed NO_WRITE_FILTER and -Wconversion build breaks (John Bowler).
+  Fix g++ build breaks (John Bowler).
+  Quieted some Coverity issues in pngfix.c, png-fix-itxt.c, pngvalid.c,
+    pngstest.c, and pngimage.c. Most seem harmless, but png-fix-itxt
+    would only work with iTXt chunks with length 255 or less.
+  Added #ifdef's to contrib/examples programs so people don't try
+    to compile them without the minimum required support enabled
+    (suggested by Flavio Medeiros).
+
+Version 1.6.18beta08 [June 30, 2015]
+  Eliminated the final two Coverity defects (insecure temporary file
+    handling in contrib/libtests/pngstest.c; possible overflow of
+    unsigned char in contrib/tools/png-fix-itxt.c). To use the "secure"
+    file handling, define PNG_USE_MKSTEMP, otherwise "tmpfile()" will
+    be used.
+  Removed some unused WEIGHTED_FILTER macros from png.h and pngstruct.h
+
+Version 1.6.18beta09 [July 5, 2015]
+  Removed some useless typecasts from contrib/tools/png-fix-itxt.c
+  Fixed a new signed-unsigned comparison in pngrtran.c (Max Stepin).
+  Replaced arbitrary use of 'extern' with #define PNG_LINKAGE_*.  To
+    preserve API compatibility, the new defines all default to "extern"
+    (requested by Jan Nijtmans).
+
+Version 1.6.18rc01 [July 9, 2015]
+  Belatedly added Mans Rullgard and James Yu to the list of Contributing
+    Authors.
+
+Version 1.6.18rc02 [July 12, 2015]
+  Restored unused FILTER_HEURISTIC macros removed at libpng-1.6.18beta08
+    to png.h to avoid compatibility warnings.
+
+Version 1.6.18rc03 [July 15, 2015]
+  Minor changes to the man page
+
+Version 1.6.18 [July 23, 2015]
+  No changes.

 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -261,7 +261,7 @@ endif(NOT WIN32 OR CYGWIN OR MINGW)
 # SET UP LINKS
 if(PNG_SHARED)
  set_target_properties(${PNG_LIB_NAME} PROPERTIES
-#   VERSION 16.${PNGLIB_RELEASE}.1.6.18beta04
+#   VERSION 16.${PNGLIB_RELEASE}.1.6.18
    VERSION 16.${PNGLIB_RELEASE}.0
    SOVERSION 16
    CLEAN_DIRECT_OUTPUT 1)
--- a/48
+++ b/48
@@ -10,21 +10,17 @@ this sentence.

 This code is released under the libpng license.

-libpng versions 1.2.6, August 15, 2004, through 1.6.18beta04, May 20, 2015, are
-Copyright (c) 2004, 2006-2015 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
-
-   Cosmin Truta
-
-libpng versions 1.0.7, July 1, 2000, through 1.2.5 - October 3, 2002, are
-Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are
+libpng versions 1.0.7, July 1, 2000, through 1.6.18, July 23, 2015, are
+Copyright (c) 2000-2002, 2004, 2006-2015 Glenn Randers-Pehrson, and are
 distributed according to the same disclaimer and license as libpng-1.0.6
-with the following individuals added to the list of Contributing Authors
+with the following individuals added to the list of Contributing Authors:

   Simon-Pierre Cadieux
   Eric S. Raymond
+   Mans Rullgard
+   Cosmin Truta
   Gilles Vollant
+   James Yu

 and with the following additions to the disclaimer:

@@ -36,17 +32,17 @@ and with the following additions to the disclaimer:
   the user.

 libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
-Copyright (c) 1998, 1999 Glenn Randers-Pehrson, and are
-distributed according to the same disclaimer and license as libpng-0.96,
-with the following individuals added to the list of Contributing Authors:
+Copyright (c) 1998-2000 Glenn Randers-Pehrson, and are distributed according
+to the same disclaimer and license as libpng-0.96, with the following
+individuals added to the list of Contributing Authors:

   Tom Lane
   Glenn Randers-Pehrson
   Willem van Schaik

 libpng versions 0.89, June 1996, through 0.96, May 1997, are
-Copyright (c) 1996, 1997 Andreas Dilger
-Distributed according to the same disclaimer and license as libpng-0.88,
+Copyright (c) 1996-1997 Andreas Dilger, and are
+distributed according to the same disclaimer and license as libpng-0.88,
 with the following individuals added to the list of Contributing Authors:

   John Bowler
@@ -57,7 +53,7 @@ with the following individuals added to the list of Contributing Authors:
   Tom Tanner

 libpng versions 0.5, May 1995, through 0.88, January 1996, are
-Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
+Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.

 For the purposes of this copyright and license, "Contributing Authors"
 is defined as the following set of individuals:
@@ -80,13 +76,13 @@ Permission is hereby granted to use, copy, modify, and distribute this
 source code, or portions hereof, for any purpose, without fee, subject
 to the following restrictions:

-1. The origin of this source code must not be misrepresented.
+  1. The origin of this source code must not be misrepresented.

-2. Altered versions must be plainly marked as such and must not
-   be misrepresented as being the original source.
+  2. Altered versions must be plainly marked as such and must not
+     be misrepresented as being the original source.

-3. This Copyright notice may not be removed or altered from any
-   source or altered source distribution.
+  3. This Copyright notice may not be removed or altered from any
+     source or altered source distribution.

 The Contributing Authors and Group 42, Inc. specifically permit, without
 fee, and encourage the use of this source code as a component to
@@ -94,18 +90,18 @@ supporting the PNG file format in commercial products.  If you use this
 source code in a product, acknowledgment is not required but would be
 appreciated.

-
 A "png_get_copyright" function is available, for convenient use in "about"
 boxes and the like:

-   printf("%s",png_get_copyright(NULL));
+   printf("%s", png_get_copyright(NULL));

 Also, the PNG logo (in PNG format, of course) is supplied in the
 files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).

-Libpng is OSI Certified Open Source Software.  OSI Certified Open Source is a
-certification mark of the Open Source Initiative.
+Libpng is OSI Certified Open Source Software.  OSI Certified Open Source is
+a certification mark of the Open Source Initiative. OSI has not addressed
+the additional disclaimers inserted at version 1.0.7.

 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-May 20, 2015
+July 23, 2015
--- a/2
+++ b/2
@@ -1,4 +1,4 @@
-README for libpng version 1.6.18beta04 - May 20, 2015 (shared library 16.0)
+README for libpng version 1.6.18 - July 23, 2015 (shared library 16.0)
 See the note about version numbers near the top of png.h

 See INSTALL for instructions on how to install libpng.
--- a/configure.ac
+++ b/configure.ac
@@ -18,7 +18,7 @@ AC_PREREQ([2.68])

 dnl Version number stuff here:

-AC_INIT([libpng],[1.6.18beta04],[png-mng-implement@lists.sourceforge.net])
+AC_INIT([libpng],[1.6.18],[png-mng-implement@lists.sourceforge.net])
 AC_CONFIG_MACRO_DIR([scripts])

 # libpng does not follow GNU file name conventions (hence 'foreign')
@@ -39,7 +39,7 @@ dnl automake, so the following is not necessary (and is not defined anyway):
 dnl AM_PREREQ([1.11.2])
 dnl stop configure from automagically running automake

-PNGLIB_VERSION=1.6.18beta04
+PNGLIB_VERSION=1.6.18
 PNGLIB_MAJOR=1
 PNGLIB_MINOR=6
 PNGLIB_RELEASE=18
--- a/contrib/arm-neon/README
+++ b/contrib/arm-neon/README
@@ -1,7 +1,7 @@
 OPERATING SYSTEM SPECIFIC ARM NEON DETECTION
 --------------------------------------------

-Detection of the ability to exexcute ARM NEON on an ARM processor requires
+Detection of the ability to execute ARM NEON on an ARM processor requires
 operating system support.  (The information is not available in user mode.)

 HOW TO USE THIS
--- a/contrib/examples/iccfrompng.c
+++ b/contrib/examples/iccfrompng.c
@@ -26,6 +26,10 @@

 #include <png.h>

+#if defined(PNG_READ_SUPPORTED) && defined(PNG_STDIO_SUPPORTED) && \
+    defined (PNG_iCCP_SUPPORTED)
+
+
 static int verbose = 1;
 static png_byte no_profile[] = "no profile";

@@ -178,3 +182,4 @@ main(int argc, char **argv)
   /* Exit code is true if any extract succeeds */
   return extracted == 0;
 }
+#endif /* READ && STDIO && iCCP */
--- a/contrib/examples/pngpixel.c
+++ b/contrib/examples/pngpixel.c
@@ -27,6 +27,8 @@
 */
 #include "../../png.h"

+#if defined(PNG_READ_SUPPORTED) && defined(PNG_SEQUENTIAL_READ_SUPPORTED)
+
 /* Return component 'c' of pixel 'x' from the given row. */
 static unsigned int
 component(png_const_bytep row, png_uint_32 x, unsigned int c,
@@ -366,3 +368,4 @@ int main(int argc, const char **argv)

   return result;
 }
+#endif /* READ && SEQUENTIAL_READ */
--- a/contrib/examples/pngtopng.c
+++ b/contrib/examples/pngtopng.c
@@ -20,6 +20,8 @@
 * ensure the code picks up the local libpng implementation:
 */
 #include "../../png.h"
+#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && \
+    defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)

 int main(int argc, const char **argv)
 {
@@ -90,3 +92,4 @@ int main(int argc, const char **argv)

   return result;
 }
+#endif /* READ && WRITE */
--- a/contrib/examples/simpleover.c
+++ b/contrib/examples/simpleover.c
@@ -44,6 +44,8 @@
 */
 #include "../../png.h"

+#ifdef PNG_SIMPLIFIED_READ_SUPPORTED
+
 #define sprite_name_chars 15
 struct sprite {
   FILE         *file;
@@ -643,3 +645,4 @@ int main(int argc, const char **argv)

   return result;
 }
+#endif /* SIMPLIFIED_READ */
--- a/contrib/libtests/pngimage.c
+++ b/contrib/libtests/pngimage.c
@@ -1,8 +1,8 @@
 /* pngimage.c
 *
- * Copyright (c) 2014 John Cunningham Bowler
+ * Copyright (c) 2015 John Cunningham Bowler
 *
- * Last changed in libpng 1.6.10 [March 6, 2014]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
@@ -1120,8 +1120,8 @@ compare_read(struct display *dp, int applied_transforms)
         {
            int b;

-            case 16: /* Two bytes per component, bit-endian */
-               for (b = (bpp >> 4); b > 0; )
+            case 16: /* Two bytes per component, big-endian */
+               for (b = (bpp >> 4); b > 0; --b)
               {
                  unsigned int sig = (unsigned int)(0xffff0000 >> sig_bits[b]);

--- a/contrib/libtests/pngstest.c
+++ b/contrib/libtests/pngstest.c
@@ -1,9 +1,9 @@
 /*-
 * pngstest.c
 *
- * Copyright (c) 2013-2014 John Cunningham Bowler
+ * Copyright (c) 2013-2015 John Cunningham Bowler
 *
- * Last changed in libpng 1.6.16 [December 22, 2014]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
@@ -615,7 +615,7 @@ freeimage(Image *image)

   if (image->tmpfile_name[0] != 0 && (image->opts & KEEP_TMPFILES) == 0)
   {
-      remove(image->tmpfile_name);
+      (void)remove(image->tmpfile_name);
      image->tmpfile_name[0] = 0;
   }
 }
@@ -2828,7 +2828,7 @@ compare_two_images(Image *a, Image *b, int via_linear,

            else if (y >= b->image.colormap_entries)
            {
-               if ((a->opts & ACCUMULATE) == 0)
+               if ((b->opts & ACCUMULATE) == 0)
                  {
                  char pindex[9];
                  sprintf(pindex, "%lu[%lu]", (unsigned long)y,
@@ -3175,7 +3175,9 @@ read_one_file(Image *image)

               if (cb > 0)
               {
+#ifndef __COVERITY__
                  if ((unsigned long int)cb <= (size_t)~(size_t)0)
+#endif
                  {
                     png_bytep b = voidcast(png_bytep, malloc((size_t)cb));

@@ -3243,8 +3245,41 @@ write_one_file(Image *output, Image *image, int convert_to_8bit)

   if (image->opts & USE_STDIO)
   {
+#ifndef PNG_USE_MKSTEMP
      FILE *f = tmpfile();
-
+#else
+      /* Experimental. Coverity says tmpfile() is insecure because it
+       * generates predictable names.
+       *
+       * It is possible to satisfy Coverity by using mkstemp(); however,
+       * any platform supporting mkstemp() undoubtedly has a secure tmpfile()
+       * implementation as well, and doesn't need the fix.  Note that
+       * the fix won't work on platforms that don't support mkstemp().
+       *
+       * https://www.securecoding.cert.org/confluence/display/c/
+       * FIO21-C.+Do+not+create+temporary+files+in+shared+directories
+       * says that most historic implementations of tmpfile() provide
+       * only a limited number of possible temporary file names
+       * (usually 26) before file names are recycled. That article also
+       * provides a secure solution that unfortunately depends upon mkstemp().
+       */
+      char tmpfile[] = "pngstest-XXXXXX";
+      int filedes;
+      FILE *f;
+      umask(0177);
+      filedes = mkstemp(tmpfile);
+      if (filedes < 0)
+        f = NULL;
+      else
+      {
+        f = fdopen(filedes,"w+");
+        /* Hide the filename immediately and ensure that the file does
+         * not exist after the program ends
+         */
+        (void) unlink(tmpfile);
+      }
+#endif
+      
      if (f != NULL)
      {
         if (png_image_write_to_stdio(&image->image, f, convert_to_8bit,
@@ -3588,7 +3623,7 @@ main(int argc, char **argv)
            }

            /* Safe: checked above */
-            strcpy(tmpf, argv[c]);
+            strncpy(tmpf, argv[c], sizeof (tmpf)-1);
         }

         else
--- a/contrib/libtests/pngvalid.c
+++ b/contrib/libtests/pngvalid.c
@@ -1,7 +1,7 @@

 /* pngvalid.c - validate libpng by constructing then reading png files.
 *
- * Last changed in libpng 1.6.17 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 * Copyright (c) 2014-2015 Glenn Randers-Pehrson
 * Written by John Cunningham Bowler
 *
@@ -1319,7 +1319,10 @@ store_current_palette(png_store *ps, int *npalette)
    * operation.)
    */
   if (ps->current == NULL)
+   {
      store_log(ps, ps->pread, "no current stream for palette", 1);
+      return NULL;
+   }

   /* The result may be null if there is no palette. */
   *npalette = ps->current->npalette;
@@ -4097,7 +4100,7 @@ make_error(png_store* volatile psIn, png_byte PNG_CONST colour_type,

   Try
   {
-      png_structp pp;
+      volatile png_structp pp;
      png_infop pi;

      pp = set_store_for_write(ps, &pi, name);
--- a/contrib/tools/genpng.c
+++ b/contrib/tools/genpng.c
@@ -79,6 +79,8 @@
 */
 #include "../../png.h"

+#if defined(PNG_SIMPLIFIED_WRITE_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
+
 static const struct color
 {
   const char *name;
@@ -862,3 +864,4 @@ main(int argc, const char **argv)

   return 1;
 }
+#endif /* SIMPLIFIED_WRITE && STDIO */
--- a/contrib/tools/png-fix-itxt.c
+++ b/contrib/tools/png-fix-itxt.c
@@ -1,8 +1,8 @@

 /* png-fix-itxt version 1.0.0
 *
- * Copyright 2013 Glenn Randers-Pehrson
- * Last changed in libpng 1.6.3 [July 18, 2013]
+ * Copyright 2015 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
@@ -34,8 +34,10 @@

 #define MAX_LENGTH 500000

-#define GETBREAK ((unsigned char)(inchar=getchar())); if (inchar == EOF) break
-
+/* Read one character (inchar), also return octet (c), break if EOF */
+#define GETBREAK inchar=getchar(); \
+                 c=(inchar & 0xffU);\
+                 if (inchar != c) break
 int
 main(void)
 {
@@ -48,25 +50,25 @@ main(void)
 /* Skip 8-byte signature */
   for (i=8; i; i--)
   {
-      c=GETBREAK;
+      GETBREAK;
      putchar(c);
   }

-if (inchar != EOF)
+if (inchar == c) /* !EOF */
 for (;;)
 {
   /* Read the length */
   unsigned long length; /* must be 32 bits! */
-   c=GETBREAK; buf[0] = c; length  = c; length <<= 8;
-   c=GETBREAK; buf[1] = c; length += c; length <<= 8;
-   c=GETBREAK; buf[2] = c; length += c; length <<= 8;
-   c=GETBREAK; buf[3] = c; length += c;
+   GETBREAK; buf[0] = c; length  = c; length <<= 8;
+   GETBREAK; buf[1] = c; length += c; length <<= 8;
+   GETBREAK; buf[2] = c; length += c; length <<= 8;
+   GETBREAK; buf[3] = c; length += c;

   /* Read the chunkname */
-   c=GETBREAK; buf[4] = c;
-   c=GETBREAK; buf[5] = c;
-   c=GETBREAK; buf[6] = c;
-   c=GETBREAK; buf[7] = c;
+   GETBREAK; buf[4] = c;
+   GETBREAK; buf[5] = c;
+   GETBREAK; buf[6] = c;
+   GETBREAK; buf[7] = c;


   /* The iTXt chunk type expressed as integers is (105, 84, 88, 116) */
@@ -81,19 +83,22 @@ for (;;)
      /* Copy the data bytes */
      for (i=8; i < length + 12; i++)
      {
-         c=GETBREAK; buf[i] = c;
+         GETBREAK; buf[i] = c;
      }

+      if (inchar != c) /* EOF */
+         break;
+
      /* Calculate the CRC */
      crc = crc32(crc, buf+4, (uInt)length+4);

      for (;;)
      {
        /* Check the CRC */
-        if (((crc >> 24) & 0xff) == buf[length+8] &&
-            ((crc >> 16) & 0xff) == buf[length+9] &&
-            ((crc >>  8) & 0xff) == buf[length+10] &&
-            ((crc      ) & 0xff) == buf[length+11])
+        if (((crc >> 24) & 0xffU) == buf[length+8] &&
+            ((crc >> 16) & 0xffU) == buf[length+9] &&
+            ((crc >>  8) & 0xffU) == buf[length+10] &&
+            ((crc      ) & 0xffU) == buf[length+11])
           break;

        length++;
@@ -101,18 +106,21 @@ for (;;)
        if (length >= MAX_LENGTH-12)
           break;

-        c=GETBREAK;
-        buf[length+11]=c;
+        GETBREAK;
+        buf[length+11] = c;

        /* Update the CRC */
        crc = crc32(crc, buf+7+length, 1);
      }

+      if (inchar != c) /* EOF */
+         break;
+
      /* Update length bytes */
-      buf[0] = (unsigned char)((length << 24) & 0xff);
-      buf[1] = (unsigned char)((length << 16) & 0xff);
-      buf[2] = (unsigned char)((length <<  8) & 0xff);
-      buf[3] = (unsigned char)((length      ) & 0xff);
+      buf[0] = (unsigned char)((length >> 24) & 0xffU);
+      buf[1] = (unsigned char)((length >> 16) & 0xffU);
+      buf[2] = (unsigned char)((length >>  8) & 0xffU);
+      buf[3] = (unsigned char)((length      ) & 0xffU);

      /* Write the fixed iTXt chunk (length, name, data, crc) */
      for (i=0; i<length+12; i++)
@@ -121,6 +129,9 @@ for (;;)

   else
   {
+      if (inchar != c) /* EOF */
+         break;
+
      /* Copy bytes that were already read (length and chunk name) */
      for (i=0; i<8; i++)
         putchar(buf[i]);
@@ -128,11 +139,11 @@ for (;;)
      /* Copy data bytes and CRC */
      for (i=8; i< length+12; i++)
      {
-         c=GETBREAK;
+         GETBREAK;
         putchar(c);
      }

-      if (inchar == EOF)
+      if (inchar != c) /* EOF */
      {
         break;
      }
@@ -142,7 +153,7 @@ for (;;)
         break;
   }

-   if (inchar == EOF)
+   if (inchar != c) /* EOF */
      break;

   if (buf[4] == 73 && buf[5] == 69 && buf[6] == 78 && buf[7] == 68)
--- a/contrib/tools/pngfix.c
+++ b/contrib/tools/pngfix.c
@@ -2,7 +2,7 @@
 *
 * Copyright (c) 2014-2015 John Cunningham Bowler
 *
- * Last changed in libpng 1.6.17 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
@@ -71,8 +71,8 @@
 * with older builds.
 */
 #if ZLIB_VERNUM < 0x1260
-#  define PNGZ_MSG_CAST(s) png_constcast(char*,s)
-#  define PNGZ_INPUT_CAST(b) png_constcast(png_bytep,b)
+#  define PNGZ_MSG_CAST(s) constcast(char*,s)
+#  define PNGZ_INPUT_CAST(b) constcast(png_bytep,b)
 #else
 #  define PNGZ_MSG_CAST(s) (s)
 #  define PNGZ_INPUT_CAST(b) (b)
@@ -86,17 +86,17 @@

 /* Copied from pngpriv.h */
 #ifdef __cplusplus
-#  define png_voidcast(type, value) static_cast<type>(value)
-#  define png_constcast(type, value) const_cast<type>(value)
-#  define png_aligncast(type, value) \
+#  define voidcast(type, value) static_cast<type>(value)
+#  define constcast(type, value) const_cast<type>(value)
+#  define aligncast(type, value) \
   static_cast<type>(static_cast<void*>(value))
-#  define png_aligncastconst(type, value) \
+#  define aligncastconst(type, value) \
   static_cast<type>(static_cast<const void*>(value))
 #else
-#  define png_voidcast(type, value) (value)
-#  define png_constcast(type, value) ((type)(value))
-#  define png_aligncast(type, value) ((void*)(value))
-#  define png_aligncastconst(type, value) ((const void*)(value))
+#  define voidcast(type, value) (value)
+#  define constcast(type, value) ((type)(value))
+#  define aligncast(type, value) ((void*)(value))
+#  define aligncastconst(type, value) ((const void*)(value))
 #endif /* __cplusplus */

 #if PNG_LIBPNG_VER < 10700
@@ -446,7 +446,7 @@ static void
 make_random_bytes(png_uint_32* seed, void* pv, size_t size)
 {
   png_uint_32 u0 = seed[0], u1 = seed[1];
-   png_bytep bytes = png_voidcast(png_bytep, pv);
+   png_bytep bytes = voidcast(png_bytep, pv);

   /* There are thirty-three bits; the next bit in the sequence is bit-33 XOR
    * bit-20.  The top 1 bit is in u1, the bottom 32 are in u0.
@@ -668,7 +668,7 @@ IDAT_list_extend(struct IDAT_list *tail)
      if (length < tail->length) /* arithmetic overflow */
         length = tail->length;
            
-      next = png_voidcast(IDAT_list*, malloc(IDAT_list_size(NULL, length)));
+      next = voidcast(IDAT_list*, malloc(IDAT_list_size(NULL, length)));
      CLEAR(*next);

      /* The caller must handle this: */
@@ -3535,7 +3535,7 @@ get_control(png_const_structrp png_ptr)
   /* This just returns the (file*).  The chunk and idat control structures
    * don't always exist.
    */
-   struct control *control = png_voidcast(struct control*,
+   struct control *control = voidcast(struct control*,
      png_get_error_ptr(png_ptr));
   return &control->file;
 }
@@ -3543,7 +3543,7 @@ get_control(png_const_structrp png_ptr)
 static void
 allocate(struct file *file, int allocate_idat)
 {
-   struct control *control = png_voidcast(struct control*, file->alloc_ptr);
+   struct control *control = voidcast(struct control*, file->alloc_ptr);

   if (allocate_idat)
   {
@@ -3853,6 +3853,7 @@ usage(const char *prog)
 int
 main(int argc, const char **argv)
 {
+   char temp_name[FILENAME_MAX+1];
   const char *  prog = *argv;
   const char *  outfile = NULL;
   const char *  suffix = NULL;
@@ -3955,7 +3956,6 @@ main(int argc, const char **argv)
      else
      {
         size_t outlen = strlen(*argv);
-         char temp_name[FILENAME_MAX+1];

         if (outfile == NULL) /* else this takes precedence */
         {
--- a/contrib/visupng/cexcept.h
+++ b/contrib/visupng/cexcept.h
@@ -1,11 +1,12 @@
 /*===
-cexcept.h 2.0.1 (2008-Jul-19-Sat)
+cexcept.h 2.0.1 (2008-Jul-19-Sat, modified 2015-Jun-03-Mon)
 http://www.nicemice.net/cexcept/
 Adam M. Costello
 http://www.nicemice.net/amc/

 An interface for exception-handling in ANSI C (C89 and subsequent ISO
-standards), developed jointly with Cosmin Truta.
+standards), developed jointly with Cosmin Truta.  Revised by John Bowler,
+June 2015, to declare exception_env and exception_prev "volatile".

    Copyright (c) 2000-2008 Adam M. Costello and Cosmin Truta.
    This software may be modified only if its author and version
@@ -210,7 +211,7 @@ struct exception_context { \

 #define Try \
  { \
-    jmp_buf *exception__prev, exception__env; \
+    jmp_buf * volatile exception__prev, exception__env; \
    exception__prev = the_exception_context->penv; \
    the_exception_context->penv = &exception__env; \
    if (setjmp(exception__env) == 0) { \
--- a/libpng-manual.txt
+++ b/libpng-manual.txt
@@ -1,6 +1,6 @@
 libpng-manual.txt - A description on how to use and modify libpng

- libpng version 1.6.18beta04 - May 20, 2015
+ libpng version 1.6.18 - July 23, 2015
 Updated and distributed by Glenn Randers-Pehrson
 <glennrp at users.sourceforge.net>
 Copyright (c) 1998-2015 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 1.6.18beta04 - May 20, 2015
+ libpng versions 0.97, January 1998, through 1.6.18 - July 23, 2015
 Updated and distributed by Glenn Randers-Pehrson
 Copyright (c) 1998-2015 Glenn Randers-Pehrson

@@ -4357,41 +4357,6 @@ is called for the first time.)
              same as the value of filter_method used
              in png_set_IHDR().

-It is also possible to influence how libpng chooses from among the
-available filters.  This is done in one or both of two ways - by
-telling it how important it is to keep the same filter for successive
-rows, and by telling it the relative computational costs of the filters.
-
-    double weights[3] = {1.5, 1.3, 1.1},
-       costs[PNG_FILTER_VALUE_LAST] =
-       {1.0, 1.3, 1.3, 1.5, 1.7};
-
-    png_set_filter_heuristics(png_ptr,
-       PNG_FILTER_HEURISTIC_WEIGHTED, 3,
-       weights, costs);
-
-The weights are multiplying factors that indicate to libpng that the
-row filter should be the same for successive rows unless another row filter
-is that many times better than the previous filter.  In the above example,
-if the previous 3 filters were SUB, SUB, NONE, the SUB filter could have a
-"sum of absolute differences" 1.5 x 1.3 times higher than other filters
-and still be chosen, while the NONE filter could have a sum 1.1 times
-higher than other filters and still be chosen.  Unspecified weights are
-taken to be 1.0, and the specified weights should probably be declining
-like those above in order to emphasize recent filters over older filters.
-
-The filter costs specify for each filter type a relative decoding cost
-to be considered when selecting row filters.  This means that filters
-with higher costs are less likely to be chosen over filters with lower
-costs, unless their "sum of absolute differences" is that much smaller.
-The costs do not necessarily reflect the exact computational speeds of
-the various filters, since this would unduly influence the final image
-size.
-
-Note that the numbers above were invented purely for this example and
-are given only to help explain the function usage.  Little testing has
-been done to find optimum values for either the costs or the weights.
-
 Requesting debug printout

 The macro definition PNG_DEBUG can be used to request debugging
@@ -5297,13 +5262,13 @@ Other rules can be inferred by inspecting the libpng source.

 XVI. Y2K Compliance in libpng

-May 20, 2015
+July 23, 2015

 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 1.6.18beta04 are Y2K compliant.  It is my belief that earlier
+upward through 1.6.18 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
--- a/libpng.3
+++ b/libpng.3
@@ -1,6 +1,6 @@
-.TH LIBPNG 3 "May 20, 2015"
+.TH LIBPNG 3 "July 23, 2015"
 .SH NAME
-libpng \- Portable Network Graphics (PNG) Reference Library 1.6.18beta04
+libpng \- Portable Network Graphics (PNG) Reference Library 1.6.18
 .SH SYNOPSIS
 \fB
 #include <png.h>\fP
@@ -119,6 +119,8 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.6.18beta04

 \fBpng_byte png_get_libpng_ver (png_const_structp \fIpng_ptr\fP\fB);\fP

+\fBint png_get_palette_max(png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
+
 \fBpng_voidp png_get_mem_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP

 \fBpng_uint_32 png_get_oFFs (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*offset_x\fP\fB, png_uint_32 \fP\fI*offset_y\fP\fB, int \fI*unit_type\fP\fB);\fP
@@ -369,6 +371,8 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.6.18beta04

 \fBvoid png_set_oFFs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIoffset_x\fP\fB, png_uint_32 \fP\fIoffset_y\fP\fB, int \fIunit_type\fP\fB);\fP

+\fBint png_set_option(png_structrp \fP\fIpng_ptr\fP\fB, int \fP\fIoption\fP\fB, int \fIonoff\fP\fB);\fP
+
 \fBvoid png_set_packing (png_structp \fIpng_ptr\fP\fB);\fP

 \fBvoid png_set_packswap (png_structp \fIpng_ptr\fP\fB);\fP
@@ -504,7 +508,7 @@ 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 1.6.18beta04 - May 20, 2015
+ libpng version 1.6.18 - July 23, 2015
 Updated and distributed by Glenn Randers-Pehrson
 <glennrp at users.sourceforge.net>
 Copyright (c) 1998-2015 Glenn Randers-Pehrson
@@ -515,7 +519,7 @@ libpng-manual.txt - A description on how to use and modify libpng

 Based on:

- libpng versions 0.97, January 1998, through 1.6.18beta04 - May 20, 2015
+ libpng versions 0.97, January 1998, through 1.6.18 - July 23, 2015
 Updated and distributed by Glenn Randers-Pehrson
 Copyright (c) 1998-2015 Glenn Randers-Pehrson

@@ -4861,41 +4865,6 @@ is called for the first time.)
              same as the value of filter_method used
              in png_set_IHDR().

-It is also possible to influence how libpng chooses from among the
-available filters.  This is done in one or both of two ways - by
-telling it how important it is to keep the same filter for successive
-rows, and by telling it the relative computational costs of the filters.
-
-    double weights[3] = {1.5, 1.3, 1.1},
-       costs[PNG_FILTER_VALUE_LAST] =
-       {1.0, 1.3, 1.3, 1.5, 1.7};
-
-    png_set_filter_heuristics(png_ptr,
-       PNG_FILTER_HEURISTIC_WEIGHTED, 3,
-       weights, costs);
-
-The weights are multiplying factors that indicate to libpng that the
-row filter should be the same for successive rows unless another row filter
-is that many times better than the previous filter.  In the above example,
-if the previous 3 filters were SUB, SUB, NONE, the SUB filter could have a
-"sum of absolute differences" 1.5 x 1.3 times higher than other filters
-and still be chosen, while the NONE filter could have a sum 1.1 times
-higher than other filters and still be chosen.  Unspecified weights are
-taken to be 1.0, and the specified weights should probably be declining
-like those above in order to emphasize recent filters over older filters.
-
-The filter costs specify for each filter type a relative decoding cost
-to be considered when selecting row filters.  This means that filters
-with higher costs are less likely to be chosen over filters with lower
-costs, unless their "sum of absolute differences" is that much smaller.
-The costs do not necessarily reflect the exact computational speeds of
-the various filters, since this would unduly influence the final image
-size.
-
-Note that the numbers above were invented purely for this example and
-are given only to help explain the function usage.  Little testing has
-been done to find optimum values for either the costs or the weights.
-
 .SS Requesting debug printout

 The macro definition PNG_DEBUG can be used to request debugging
@@ -5801,13 +5770,13 @@ Other rules can be inferred by inspecting the libpng source.

 .SH XVI. Y2K Compliance in libpng

-May 20, 2015
+July 23, 2015

 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 1.6.18beta04 are Y2K compliant.  It is my belief that earlier
+upward through 1.6.18 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
@@ -6062,7 +6031,9 @@ the first widely used release:
 1.6.17beta01-06     16    10617  16.so.16.17[.0]
 1.6.17rc01-06       16    10617  16.so.16.17[.0]
 1.6.17              16    10617  16.so.16.17[.0]
- 1.6.18beta01-04     16    10618  16.so.16.18[.0]
+ 1.6.18beta01-09     16    10618  16.so.16.18[.0]
+ 1.6.18rc01-03       16    10618  16.so.16.18[.0]
+ 1.6.18              16    10618  16.so.16.18[.0]

 Henceforth the source version will match the shared-library minor
 and patch numbers; the shared-library major version number will be
@@ -6119,7 +6090,7 @@ possible without all of you.

 Thanks to Frank J. T. Wojcik for helping with the documentation.

-Libpng version 1.6.18beta04 - May 20, 2015:
+Libpng version 1.6.18 - July 23, 2015:
 Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
 Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).

@@ -6142,44 +6113,39 @@ this sentence.

 This code is released under the libpng license.

-libpng versions 1.2.6, August 15, 2004, through 1.6.18beta04, May 20, 2015, are
-Copyright (c) 2004,2006-2015 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
-
-   Cosmin Truta
-
-libpng versions 1.0.7, July 1, 2000, through 1.2.5 - October 3, 2002, are
-Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are
+libpng versions 1.0.7, July 1, 2000, through 1.6.18, July 23, 2015, are
+Copyright (c) 2000-2002, 2004, 2006-2015 Glenn Randers-Pehrson, and are
 distributed according to the same disclaimer and license as libpng-1.0.6
-with the following individuals added to the list of Contributing Authors
+with the following individuals added to the list of Contributing Authors:

   Simon-Pierre Cadieux
   Eric S. Raymond
+   Mans Rullgard
+   Cosmin Truta
   Gilles Vollant
+   James Yu

 and with the following additions to the disclaimer:

-   There is no warranty against interference with your
-   enjoyment of the library or against infringement.
-   There is no warranty that our efforts or the library
-   will fulfill any of your particular purposes or needs.
-   This library is provided with all faults, and the entire
-   risk of satisfactory quality, performance, accuracy, and
-   effort is with the user.
+   There is no warranty against interference with your enjoyment of the
+   library or against infringement.  There is no warranty that our
+   efforts or the library will fulfill any of your particular purposes
+   or needs.  This library is provided with all faults, and the entire
+   risk of satisfactory quality, performance, accuracy, and effort is with
+   the user.

 libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
-Copyright (c) 1998, 1999 Glenn Randers-Pehrson
-Distributed according to the same disclaimer and license as libpng-0.96,
-with the following individuals added to the list of Contributing Authors:
+Copyright (c) 1998-2000 Glenn Randers-Pehrson, and are distributed according
+to the same disclaimer and license as libpng-0.96, with the following
+individuals added to the list of Contributing Authors:

   Tom Lane
   Glenn Randers-Pehrson
   Willem van Schaik

 libpng versions 0.89, June 1996, through 0.96, May 1997, are
-Copyright (c) 1996, 1997 Andreas Dilger
-Distributed according to the same disclaimer and license as libpng-0.88,
+Copyright (c) 1996-1997 Andreas Dilger, and are
+distributed according to the same disclaimer and license as libpng-0.88,
 with the following individuals added to the list of Contributing Authors:

   John Bowler
@@ -6190,7 +6156,7 @@ with the following individuals added to the list of Contributing Authors:
   Tom Tanner

 libpng versions 0.5, May 1995, through 0.88, January 1996, are
-Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
+Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.

 For the purposes of this copyright and license, "Contributing Authors"
 is defined as the following set of individuals:
@@ -6213,13 +6179,13 @@ Permission is hereby granted to use, copy, modify, and distribute this
 source code, or portions hereof, for any purpose, without fee, subject
 to the following restrictions:

-1. The origin of this source code must not be misrepresented.
+  1. The origin of this source code must not be misrepresented.

-2. Altered versions must be plainly marked as such and
-   must not be misrepresented as being the original source.
+  2. Altered versions must be plainly marked as such and must not
+     be misrepresented as being the original source.

-3. This Copyright notice may not be removed or altered from
-   any source or altered source distribution.
+  3. This Copyright notice may not be removed or altered from any
+     source or altered source distribution.

 The Contributing Authors and Group 42, Inc. specifically permit, without
 fee, and encourage the use of this source code as a component to
@@ -6227,21 +6193,21 @@ supporting the PNG file format in commercial products.  If you use this
 source code in a product, acknowledgment is not required but would be
 appreciated.

-
 A "png_get_copyright" function is available, for convenient use in "about"
 boxes and the like:

-   printf("%s",png_get_copyright(NULL));
+   printf("%s", png_get_copyright(NULL));

 Also, the PNG logo (in PNG format, of course) is supplied in the
 files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).

-Libpng is OSI Certified Open Source Software.  OSI Certified Open Source is a
-certification mark of the Open Source Initiative.
+Libpng is OSI Certified Open Source Software.  OSI Certified Open Source is
+a certification mark of the Open Source Initiative. OSI has not addressed
+the additional disclaimers inserted at version 1.0.7.

 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-May 20, 2015
+July 23, 2015

 .\" end of man page

--- a/libpngpf.3
+++ b/libpngpf.3
@@ -1,6 +1,6 @@
-.TH LIBPNGPF 3 "May 20, 2015"
+.TH LIBPNGPF 3 "July 23, 2015"
 .SH NAME
-libpng \- Portable Network Graphics (PNG) Reference Library 1.6.18beta04
+libpng \- Portable Network Graphics (PNG) Reference Library 1.6.18
 (private functions)
 .SH SYNOPSIS
 \fB#include \fI"pngpriv.h"
--- a/png.5
+++ b/png.5
@@ -1,4 +1,4 @@
-.TH PNG 5 "May 20, 2015"
+.TH PNG 5 "July 23, 2015"
 .SH NAME
 png \- Portable Network Graphics (PNG) format
 .SH DESCRIPTION
--- a/png.c
+++ b/png.c
@@ -1,7 +1,7 @@

 /* png.c - location for general purpose libpng functions
 *
- * Last changed in libpng 1.6.18 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 * Copyright (c) 1998-2015 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_6_18beta04 Your_png_h_is_not_version_1_6_18beta04;
+typedef png_libpng_version_1_6_18 Your_png_h_is_not_version_1_6_18;

 /* 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
@@ -243,15 +243,15 @@ png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
      create_struct.user_height_max = PNG_USER_HEIGHT_MAX;

 #     ifdef PNG_USER_CHUNK_CACHE_MAX
-         /* Added at libpng-1.2.43 and 1.4.0 */
-         create_struct.user_chunk_cache_max = PNG_USER_CHUNK_CACHE_MAX;
+      /* Added at libpng-1.2.43 and 1.4.0 */
+      create_struct.user_chunk_cache_max = PNG_USER_CHUNK_CACHE_MAX;
 #     endif

 #     ifdef PNG_USER_CHUNK_MALLOC_MAX
-         /* Added at libpng-1.2.43 and 1.4.1, required only for read but exists
-          * in png_struct regardless.
-          */
-         create_struct.user_chunk_malloc_max = PNG_USER_CHUNK_MALLOC_MAX;
+      /* Added at libpng-1.2.43 and 1.4.1, required only for read but exists
+       * in png_struct regardless.
+       */
+      create_struct.user_chunk_malloc_max = PNG_USER_CHUNK_MALLOC_MAX;
 #     endif
 #  endif

@@ -304,10 +304,10 @@ png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
               create_struct.zstream.opaque = png_ptr;

 #              ifdef PNG_SETJMP_SUPPORTED
-                  /* Eliminate the local error handling: */
-                  create_struct.jmp_buf_ptr = NULL;
-                  create_struct.jmp_buf_size = 0;
-                  create_struct.longjmp_fn = 0;
+               /* Eliminate the local error handling: */
+               create_struct.jmp_buf_ptr = NULL;
+               create_struct.jmp_buf_size = 0;
+               create_struct.longjmp_fn = 0;
 #              endif

               *png_ptr = create_struct;
@@ -766,13 +766,13 @@ png_get_copyright(png_const_structrp png_ptr)
 #else
 #  ifdef __STDC__
   return PNG_STRING_NEWLINE \
-     "libpng version 1.6.18beta04 - May 20, 2015" PNG_STRING_NEWLINE \
-     "Copyright (c) 1998-2015 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;
+      "libpng version 1.6.18 - July 23, 2015" PNG_STRING_NEWLINE \
+      "Copyright (c) 1998-2015 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 1.6.18beta04 - May 20, 2015\
+   return "libpng version 1.6.18 - July 23, 2015\
      Copyright (c) 1998-2015 Glenn Randers-Pehrson\
      Copyright (c) 1996-1997 Andreas Dilger\
      Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
@@ -811,9 +811,9 @@ png_get_header_version(png_const_structrp png_ptr)
 #ifdef __STDC__
   return PNG_HEADER_VERSION_STRING
 #  ifndef PNG_READ_SUPPORTED
-   "     (NO READ SUPPORT)"
+      " (NO READ SUPPORT)"
 #  endif
-   PNG_STRING_NEWLINE;
+      PNG_STRING_NEWLINE;
 #else
   return PNG_HEADER_VERSION_STRING;
 #endif
@@ -1086,10 +1086,10 @@ png_colorspace_set_gamma(png_const_structrp png_ptr,
      errmsg = "gamma value out of range";

 #  ifdef PNG_READ_gAMA_SUPPORTED
-      /* Allow the application to set the gamma value more than once */
-      else if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
-         (colorspace->flags & PNG_COLORSPACE_FROM_gAMA) != 0)
-         errmsg = "duplicate";
+   /* Allow the application to set the gamma value more than once */
+   else if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
+      (colorspace->flags & PNG_COLORSPACE_FROM_gAMA) != 0)
+      errmsg = "duplicate";
 #  endif

   /* Do nothing if the colorspace is already invalid */
@@ -1130,31 +1130,31 @@ png_colorspace_sync_info(png_const_structrp png_ptr, png_inforp info_ptr)
         PNG_INFO_iCCP);

 #     ifdef PNG_COLORSPACE_SUPPORTED
-         /* Clean up the iCCP profile now if it won't be used. */
-         png_free_data(png_ptr, info_ptr, PNG_FREE_ICCP, -1/*not used*/);
+      /* Clean up the iCCP profile now if it won't be used. */
+      png_free_data(png_ptr, info_ptr, PNG_FREE_ICCP, -1/*not used*/);
 #     else
-         PNG_UNUSED(png_ptr)
+      PNG_UNUSED(png_ptr)
 #     endif
   }

   else
   {
 #     ifdef PNG_COLORSPACE_SUPPORTED
-         /* Leave the INFO_iCCP flag set if the pngset.c code has already set
-          * it; this allows a PNG to contain a profile which matches sRGB and
-          * yet still have that profile retrievable by the application.
-          */
-         if ((info_ptr->colorspace.flags & PNG_COLORSPACE_MATCHES_sRGB) != 0)
-            info_ptr->valid |= PNG_INFO_sRGB;
+      /* Leave the INFO_iCCP flag set if the pngset.c code has already set
+       * it; this allows a PNG to contain a profile which matches sRGB and
+       * yet still have that profile retrievable by the application.
+       */
+      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_MATCHES_sRGB) != 0)
+         info_ptr->valid |= PNG_INFO_sRGB;

-         else
-            info_ptr->valid &= ~PNG_INFO_sRGB;
+      else
+         info_ptr->valid &= ~PNG_INFO_sRGB;

-         if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
-            info_ptr->valid |= PNG_INFO_cHRM;
+      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
+         info_ptr->valid |= PNG_INFO_cHRM;

-         else
-            info_ptr->valid &= ~PNG_INFO_cHRM;
+      else
+         info_ptr->valid &= ~PNG_INFO_cHRM;
 #     endif

      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) != 0)
@@ -2844,7 +2844,7 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,

      if (fp >= DBL_MIN && fp <= DBL_MAX)
      {
-         int exp_b10;       /* A base 10 exponent */
+         int exp_b10;   /* A base 10 exponent */
         double base;   /* 10^exp_b10 */

         /* First extract a base 10 exponent of the number,
@@ -2892,7 +2892,7 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
          */

         {
-            int czero, clead, cdigits;
+            unsigned int czero, clead, cdigits;
            char exponent[10];

            /* Allow up to two leading zeros - this will not lengthen
@@ -2922,7 +2922,7 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
                * of the loop don't break the number into parts so
                * that the final digit is rounded.
                */
-               if (cdigits+czero-clead+1 < (int)precision)
+               if (cdigits+czero+1 < precision+clead)
                  fp = modf(fp, &d);

               else
@@ -3028,7 +3028,7 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
                  *ascii++ = (char)(48 + (int)d), ++cdigits;
               }
            }
-            while (cdigits+czero-clead < (int)precision && fp > DBL_MIN);
+            while (cdigits+czero < precision+clead && fp > DBL_MIN);

            /* The total output count (max) is now 4+precision */

@@ -3096,7 +3096,7 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
            /* Need another size check here for the exponent digits, so
             * this need not be considered above.
             */
-            if ((int)size > cdigits)
+            if (size > cdigits)
            {
               while (cdigits > 0) *ascii++ = exponent[--cdigits];

--- a/png.h
+++ b/png.h
@@ -1,7 +1,7 @@

 /* png.h - header file for PNG reference library
 *
- * libpng version 1.6.18beta04, May 20, 2015
+ * libpng version 1.6.18, July 23, 2015
 *
 * Copyright (c) 1998-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
@@ -11,8 +11,8 @@
 *
 * 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 1.6.18beta04, May 20, 2015: Glenn
+ *   libpng versions 0.89, June 1996, through 0.96, May 1997: Andreas Dilger
+ *   libpng versions 0.97, January 1998, through 1.6.18, July 23, 2015: Glenn
 *   See also "Contributing Authors", below.
 *
 * Note about libpng version numbers:
@@ -216,7 +216,9 @@
 *    1.6.17beta01-06         16    10617  16.so.16.17[.0]
 *    1.6.17rc01-06           16    10617  16.so.16.17[.0]
 *    1.6.17                  16    10617  16.so.16.17[.0]
- *    1.6.18beta01-04         16    10618  16.so.16.18[.0]
+ *    1.6.18beta01-09         16    10618  16.so.16.18[.0]
+ *    1.6.18rc01-03           16    10618  16.so.16.18[.0]
+ *    1.6.18                  16    10618  16.so.16.18[.0]
 *
 *   Henceforth the source version will match the shared-library major
 *   and minor numbers; the shared-library major version number will be
@@ -248,21 +250,16 @@
 *
 * This code is released under the libpng license.
 *
- * libpng versions 1.2.6, August 15, 2004, through 1.6.18beta04, May 20, 2015, are
- * Copyright (c) 2004, 2006-2015 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:
- *
- *    Cosmin Truta
- *
- * libpng versions 1.0.7, July 1, 2000, through 1.2.5, October 3, 2002, are
- * Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are
+ * libpng versions 1.0.7, July 1, 2000, through 1.6.18, July 23, 2015, are
+ * Copyright (c) 2000-2002, 2004, 2006-2015 Glenn Randers-Pehrson, and are
 * distributed according to the same disclaimer and license as libpng-1.0.6
 * with the following individuals added to the list of Contributing Authors:
 *
 *    Simon-Pierre Cadieux
- *    Eric S. Raymond
+ *    Mans Rullgard
+ *    Cosmin Truta
 *    Gilles Vollant
+ *    James Yu
 *
 * and with the following additions to the disclaimer:
 *
@@ -274,17 +271,18 @@
 *    the user.
 *
 * libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
- * Copyright (c) 1998, 1999, 2000 Glenn Randers-Pehrson, and are
- * distributed according to the same disclaimer and license as libpng-0.96,
- * with the following individuals added to the list of Contributing Authors:
+ * Copyright (c) 1998-2000 Glenn Randers-Pehrson, and are distributed according
+ * to the same disclaimer and license as libpng-0.96, with the following
+ * individuals added to the list of Contributing Authors:
 *
 *    Tom Lane
 *    Glenn Randers-Pehrson
+ *    Eric S. Raymond
 *    Willem van Schaik
 *
 * libpng versions 0.89, June 1996, through 0.96, May 1997, are
- * Copyright (c) 1996, 1997 Andreas Dilger
- * Distributed according to the same disclaimer and license as libpng-0.88,
+ * Copyright (c) 1996-1997 Andreas Dilger, and are
+ * distributed according to the same disclaimer and license as libpng-0.88,
 * with the following individuals added to the list of Contributing Authors:
 *
 *    John Bowler
@@ -295,7 +293,7 @@
 *    Tom Tanner
 *
 * libpng versions 0.5, May 1995, through 0.88, January 1996, are
- * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
 *
 * For the purposes of this copyright and license, "Contributing Authors"
 * is defined as the following set of individuals:
@@ -323,8 +321,8 @@
 *   2. Altered versions must be plainly marked as such and must not
 *      be misrepresented as being the original source.
 *
- *   3. This Copyright notice may not be removed or altered from
- *      any source or altered source distribution.
+ *   3. This Copyright notice may not be removed or altered from any
+ *      source or altered source distribution.
 *
 * The Contributing Authors and Group 42, Inc. specifically permit, without
 * fee, and encourage the use of this source code as a component to
@@ -337,15 +335,16 @@
 * A "png_get_copyright" function is available, for convenient use in "about"
 * boxes and the like:
 *
- *     printf("%s", png_get_copyright(NULL));
+ *    printf("%s", png_get_copyright(NULL));
 *
 * Also, the PNG logo (in PNG format, of course) is supplied in the
 * files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
 */

 /*
- * Libpng is OSI Certified Open Source Software.  OSI Certified is a
- * certification mark of the Open Source Initiative.
+ * Libpng is OSI Certified Open Source Software.  OSI Certified Open Source is
+ * a certification mark of the Open Source Initiative. OSI has not addressed
+ * the additional disclaimers inserted at version 1.0.7.
 */

 /*
@@ -360,13 +359,13 @@
 * Y2K compliance in libpng:
 * =========================
 *
- *    May 20, 2015
+ *    July 23, 2015
 *
 *    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 1.6.18beta04 are Y2K compliant.  It is my belief that
+ *    upward through 1.6.18 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
@@ -428,9 +427,9 @@
 */

 /* Version information for png.h - this should match the version in png.c */
-#define PNG_LIBPNG_VER_STRING "1.6.18beta04"
+#define PNG_LIBPNG_VER_STRING "1.6.18"
 #define PNG_HEADER_VERSION_STRING \
-     " libpng version 1.6.18beta04 - May 20, 2015\n"
+     " libpng version 1.6.18 - July 23, 2015\n"

 #define PNG_LIBPNG_VER_SONUM   16
 #define PNG_LIBPNG_VER_DLLNUM  16
@@ -444,7 +443,7 @@
 * PNG_LIBPNG_VER_STRING, omitting any leading zero:
 */

-#define PNG_LIBPNG_VER_BUILD  04
+#define PNG_LIBPNG_VER_BUILD  0

 /* Release Status */
 #define PNG_LIBPNG_BUILD_ALPHA    1
@@ -461,7 +460,7 @@
 #define PNG_LIBPNG_BUILD_SPECIAL 32 /* Cannot be OR'ed with
                                       PNG_LIBPNG_BUILD_PRIVATE */

-#define PNG_LIBPNG_BUILD_BASE_TYPE PNG_LIBPNG_BUILD_BETA
+#define PNG_LIBPNG_BUILD_BASE_TYPE PNG_LIBPNG_BUILD_STABLE

 /* Careful here.  At one time, Guy wanted to use 082, but that would be octal.
 * We must not include leading zeros.
@@ -574,7 +573,7 @@ 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_6_18beta04;
+typedef char* png_libpng_version_1_6_18;

 /* Basic control structions.  Read libpng-manual.txt or libpng.3 for more info.
 *
@@ -1624,35 +1623,7 @@ PNG_EXPORT(67, void, png_set_filter, (png_structrp png_ptr, int method,
 #define PNG_FILTER_VALUE_LAST  5

 #ifdef PNG_WRITE_SUPPORTED
-#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED /* EXPERIMENTAL */
-/* The "heuristic_method" is given by one of the PNG_FILTER_HEURISTIC_
- * defines, either the default (minimum-sum-of-absolute-differences), or
- * the experimental method (weighted-minimum-sum-of-absolute-differences).
- *
- * Weights are factors >= 1.0, indicating how important it is to keep the
- * filter type consistent between rows.  Larger numbers mean the current
- * filter is that many times as likely to be the same as the "num_weights"
- * previous filters.  This is cumulative for each previous row with a weight.
- * There needs to be "num_weights" values in "filter_weights", or it can be
- * NULL if the weights aren't being specified.  Weights have no influence on
- * the selection of the first row filter.  Well chosen weights can (in theory)
- * improve the compression for a given image.
- *
- * Costs are factors >= 1.0 indicating the relative decoding costs of a
- * filter type.  Higher costs indicate more decoding expense, and are
- * therefore less likely to be selected over a filter with lower computational
- * costs.  There needs to be a value in "filter_costs" for each valid filter
- * type (given by PNG_FILTER_VALUE_LAST), or it can be NULL if you aren't
- * setting the costs.  Costs try to improve the speed of decompression without
- * unduly increasing the compressed image size.
- *
- * A negative weight or cost indicates the default value is to be used, and
- * values in the range [0.0, 1.0) indicate the value is to remain unchanged.
- * The default values for both weights and costs are currently 1.0, but may
- * change if good general weighting/cost heuristics can be found.  If both
- * the weights and costs are set to 1.0, this degenerates the WEIGHTED method
- * to the UNWEIGHTED method, but with added encoding time/computation.
- */
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED /* DEPRECATED */
 PNG_FP_EXPORT(68, void, png_set_filter_heuristics, (png_structrp png_ptr,
    int heuristic_method, int num_weights, png_const_doublep filter_weights,
    png_const_doublep filter_costs))
@@ -1662,9 +1633,7 @@ PNG_FIXED_EXPORT(209, void, png_set_filter_heuristics_fixed,
    png_const_fixed_point_p filter_costs))
 #endif /* WRITE_WEIGHTED_FILTER */

-/* Heuristic used for row filter selection.  These defines should NOT be
- * changed.
- */
+/* The following are no longer used and will be removed from libpng-1.7: */
 #define PNG_FILTER_HEURISTIC_DEFAULT    0  /* Currently "UNWEIGHTED" */
 #define PNG_FILTER_HEURISTIC_UNWEIGHTED 1  /* Used by libpng < 0.95 */
 #define PNG_FILTER_HEURISTIC_WEIGHTED   2  /* Experimental feature */
--- a/pngconf.h
+++ b/pngconf.h
@@ -1,7 +1,7 @@

 /* pngconf.h - machine configurable file for libpng
 *
- * libpng version 1.6.18beta04, (PENDING RELEASE)
+ * libpng version 1.6.18, July 23, 2015
 *
 * Copyright (c) 1998-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
@@ -295,11 +295,11 @@
    * table entries, so we discard it here.  See the .dfn files in the
    * scripts directory.
    */
-#ifndef PNG_EXPORTA

-#  define PNG_EXPORTA(ordinal, type, name, args, attributes)\
-      PNG_FUNCTION(PNG_EXPORT_TYPE(type),(PNGAPI name),PNGARG(args), \
-        extern attributes)
+#ifndef PNG_EXPORTA
+#  define PNG_EXPORTA(ordinal, type, name, args, attributes) \
+      PNG_FUNCTION(PNG_EXPORT_TYPE(type), (PNGAPI name), PNGARG(args), \
+      PNG_LINKAGE_API attributes)
 #endif

 /* ANSI-C (C90) does not permit a macro to be invoked with an empty argument,
@@ -307,7 +307,7 @@
 */
 #define PNG_EMPTY /*empty list*/

-#define PNG_EXPORT(ordinal, type, name, args)\
+#define PNG_EXPORT(ordinal, type, name, args) \
   PNG_EXPORTA(ordinal, type, name, args, PNG_EMPTY)

 /* Use PNG_REMOVED to comment out a removed interface. */
--- a/pngpread.c
+++ b/pngpread.c
@@ -1,7 +1,7 @@

 /* pngpread.c - read a png file in push mode
 *
- * Last changed in libpng 1.6.18 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 * Copyright (c) 1998-2015 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.)
@@ -19,7 +19,6 @@
 #define PNG_READ_SIG_MODE   0
 #define PNG_READ_CHUNK_MODE 1
 #define PNG_READ_IDAT_MODE  2
-#define PNG_SKIP_MODE       3
 #define PNG_READ_tEXt_MODE  4
 #define PNG_READ_zTXt_MODE  5
 #define PNG_READ_DONE_MODE  6
@@ -78,32 +77,14 @@ png_process_data_pause(png_structrp png_ptr, int save)
 png_uint_32 PNGAPI
 png_process_data_skip(png_structrp png_ptr)
 {
-   png_uint_32 remaining = 0;
-
-   if (png_ptr != NULL && png_ptr->process_mode == PNG_SKIP_MODE &&
-      png_ptr->skip_length > 0)
-   {
-      /* At the end of png_process_data the buffer size must be 0 (see the loop
-       * above) so we can detect a broken call here:
-       */
-      if (png_ptr->buffer_size != 0)
-         png_error(png_ptr,
-            "png_process_data_skip called inside png_process_data");
-
-      /* If is impossible for there to be a saved buffer at this point -
-       * otherwise we could not be in SKIP mode.  This will also happen if
-       * png_process_skip is called inside png_process_data (but only very
-       * rarely.)
-       */
-      if (png_ptr->save_buffer_size != 0)
-         png_error(png_ptr, "png_process_data_skip called with saved data");
-
-      remaining = png_ptr->skip_length;
-      png_ptr->skip_length = 0;
-      png_ptr->process_mode = PNG_READ_CHUNK_MODE;
-   }
-
-   return remaining;
+  /* TODO: Deprecate and remove this API.
+   * Somewhere the implementation of this seems to have been lost,
+   * or abandoned.  It was only to support some internal back-door access
+   * to png_struct) in libpng-1.4.x.
+   */
+   png_app_warning(png_ptr,
+"png_process_data_skip is not implemented in any current version of libpng");
+   return 0;
 }

 /* What we do with the incoming data depends on what we were previously
@@ -135,12 +116,6 @@ png_process_some_data(png_structrp png_ptr, png_inforp info_ptr)
         break;
      }

-      case PNG_SKIP_MODE:
-      {
-         png_push_crc_finish(png_ptr);
-         break;
-      }
-
      default:
      {
         png_ptr->buffer_size = 0;
@@ -159,7 +134,7 @@ void /* PRIVATE */
 png_push_read_sig(png_structrp png_ptr, png_inforp info_ptr)
 {
   png_size_t num_checked = png_ptr->sig_bytes, /* SAFE, does not exceed 8 */ 
-             num_to_check = 8 - num_checked;
+       num_to_check = 8 - num_checked;

   if (png_ptr->buffer_size < num_to_check)
   {
@@ -439,69 +414,6 @@ png_push_read_chunk(png_structrp png_ptr, png_inforp info_ptr)
   png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
 }

-void /* PRIVATE */
-png_push_crc_skip(png_structrp png_ptr, png_uint_32 skip)
-{
-   png_ptr->process_mode = PNG_SKIP_MODE;
-   png_ptr->skip_length = skip;
-}
-
-void /* PRIVATE */
-png_push_crc_finish(png_structrp png_ptr)
-{
-   if (png_ptr->skip_length != 0 && png_ptr->save_buffer_size != 0)
-   {
-      png_size_t save_size = png_ptr->save_buffer_size;
-      png_uint_32 skip_length = png_ptr->skip_length;
-
-      /* We want the smaller of 'skip_length' and 'save_buffer_size', but
-       * they are of different types and we don't know which variable has the
-       * fewest bits.  Carefully select the smaller and cast it to the type of
-       * the larger - this cannot overflow.  Do not cast in the following test
-       * - it will break on either 16 or 64 bit platforms.
-       */
-      if (skip_length < save_size)
-         save_size = (png_size_t)skip_length;
-
-      else
-         skip_length = (png_uint_32)save_size;
-
-      png_calculate_crc(png_ptr, png_ptr->save_buffer_ptr, save_size);
-
-      png_ptr->skip_length -= skip_length;
-      png_ptr->buffer_size -= save_size;
-      png_ptr->save_buffer_size -= save_size;
-      png_ptr->save_buffer_ptr += save_size;
-   }
-   if (png_ptr->skip_length != 0 && png_ptr->current_buffer_size != 0)
-   {
-      png_size_t save_size = png_ptr->current_buffer_size;
-      png_uint_32 skip_length = png_ptr->skip_length;
-
-      /* We want the smaller of 'skip_length' and 'current_buffer_size', here,
-       * the same problem exists as above and the same solution.
-       */
-      if (skip_length < save_size)
-         save_size = (png_size_t)skip_length;
-
-      else
-         skip_length = (png_uint_32)save_size;
-
-      png_calculate_crc(png_ptr, png_ptr->current_buffer_ptr, save_size);
-
-      png_ptr->skip_length -= skip_length;
-      png_ptr->buffer_size -= save_size;
-      png_ptr->current_buffer_size -= save_size;
-      png_ptr->current_buffer_ptr += save_size;
-   }
-   if (png_ptr->skip_length == 0)
-   {
-      PNG_PUSH_SAVE_BUFFER_IF_LT(4)
-      png_crc_finish(png_ptr, 0);
-      png_ptr->process_mode = PNG_READ_CHUNK_MODE;
-   }
-}
-
 void PNGCBAPI
 png_push_fill_buffer(png_structp png_ptr, png_bytep buffer, png_size_t length)
 {
@@ -694,6 +606,7 @@ png_push_read_IDAT(png_structrp png_ptr)
      png_ptr->current_buffer_size -= save_size;
      png_ptr->current_buffer_ptr += save_size;
   }
+
   if (png_ptr->idat_size == 0)
   {
      PNG_PUSH_SAVE_BUFFER_IF_LT(4)
--- a/pngpriv.h
+++ b/pngpriv.h
@@ -1,7 +1,7 @@

 /* pngpriv.h - private declarations for use inside libpng
 *
- * Last changed in libpng 1.6.18 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 * Copyright (c) 1998-2015 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.)
@@ -252,17 +252,18 @@
 * always be used to declare an extern data or function object in this file.
 */
 #ifndef PNG_INTERNAL_DATA
-#  define PNG_INTERNAL_DATA(type, name, array) extern type name array
+#  define PNG_INTERNAL_DATA(type, name, array) PNG_LINKAGE_DATA type name array
 #endif

 #ifndef PNG_INTERNAL_FUNCTION
 #  define PNG_INTERNAL_FUNCTION(type, name, args, attributes)\
-      extern PNG_FUNCTION(type, name, args, PNG_EMPTY attributes)
+      PNG_LINKAGE_FUNCTION PNG_FUNCTION(type, name, args, PNG_EMPTY attributes)
 #endif

 #ifndef PNG_INTERNAL_CALLBACK
 #  define PNG_INTERNAL_CALLBACK(type, name, args, attributes)\
-      extern PNG_FUNCTION(type, (PNGCBAPI name), args, PNG_EMPTY attributes)
+      PNG_LINKAGE_CALLBACK PNG_FUNCTION(type, (PNGCBAPI name), args,\
+         PNG_EMPTY attributes)
 #endif

 /* If floating or fixed point APIs are disabled they may still be compiled
@@ -1392,10 +1393,6 @@ PNG_INTERNAL_FUNCTION(void,png_push_read_chunk,(png_structrp png_ptr,
 PNG_INTERNAL_FUNCTION(void,png_push_read_sig,(png_structrp png_ptr,
    png_inforp info_ptr),PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(void,png_push_check_crc,(png_structrp png_ptr),PNG_EMPTY);
-PNG_INTERNAL_FUNCTION(void,png_push_crc_skip,(png_structrp png_ptr,
-    png_uint_32 length),PNG_EMPTY);
-PNG_INTERNAL_FUNCTION(void,png_push_crc_finish,(png_structrp png_ptr),
-    PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(void,png_push_save_buffer,(png_structrp png_ptr),
    PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(void,png_push_restore_buffer,(png_structrp png_ptr,
--- a/pngread.c
+++ b/pngread.c
@@ -1043,9 +1043,9 @@ png_read_png(png_structrp png_ptr, png_inforp info_ptr,
   /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
    */
   if ((transforms & PNG_TRANSFORM_SCALE_16) != 0)
-     /* 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.
-      */
+      /* 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.
+       */
 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
      png_set_scale_16(png_ptr);
 #else
@@ -1209,7 +1209,7 @@ png_read_png(png_structrp png_ptr, png_inforp info_ptr,

      for (iptr = 0; iptr < info_ptr->height; iptr++)
         info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
-            png_malloc(png_ptr, info_ptr->rowbytes));
+             png_malloc(png_ptr, info_ptr->rowbytes));
   }

   png_read_image(png_ptr, info_ptr->row_pointers);
--- a/pngrtran.c
+++ b/pngrtran.c
@@ -1,7 +1,7 @@

 /* pngrtran.c - transforms the data in a row for PNG readers
 *
- * Last changed in libpng 1.6.18 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 * Copyright (c) 1998-2015 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.)
@@ -4460,7 +4460,7 @@ png_do_expand(png_row_infop row_info, png_bytep row,

               for (i = 0; i < row_width; i++)
               {
-                  if ((*sp & 0xff) == gray)
+                  if ((*sp & 0xffU) == gray)
                     *dp-- = 0;

                  else
@@ -4478,8 +4478,8 @@ png_do_expand(png_row_infop row_info, png_bytep row,
               dp = row + (row_info->rowbytes << 1) - 1;
               for (i = 0; i < row_width; i++)
               {
-                  if ((*(sp - 1) & 0xff) == gray_high &&
-                      (*(sp) & 0xff) == gray_low)
+                  if ((*(sp - 1) & 0xffU) == gray_high &&
+                      (*(sp) & 0xffU) == gray_low)
                  {
                     *dp-- = 0;
                     *dp-- = 0;
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -1,7 +1,7 @@

 /* pngrutil.c - utilities to read a PNG file
 *
- * Last changed in libpng 1.6.18 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 * Copyright (c) 1998-2015 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.)
@@ -1146,11 +1146,13 @@ png_handle_sBIT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
      return;

   for (i=0; i<truelen; ++i)
+   {
      if (buf[i] == 0 || buf[i] > sample_depth)
      {
         png_chunk_benign_error(png_ptr, "invalid");
         return;
      }
+   }

   if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
   {
@@ -1461,10 +1463,10 @@ png_handle_iCCP(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
                                    finished = 1;

 #                                   ifdef PNG_sRGB_SUPPORTED
-                                       /* Check for a match against sRGB */
-                                       png_icc_set_sRGB(png_ptr,
-                                          &png_ptr->colorspace, profile,
-                                          png_ptr->zstream.adler);
+                                    /* Check for a match against sRGB */
+                                    png_icc_set_sRGB(png_ptr,
+                                       &png_ptr->colorspace, profile,
+                                       png_ptr->zstream.adler);
 #                                   endif

                                    /* Steal the profile for info_ptr. */
@@ -1674,8 +1676,8 @@ png_handle_sPLT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)

   if (dl > max_dl)
   {
-       png_warning(png_ptr, "sPLT chunk too long");
-       return;
+      png_warning(png_ptr, "sPLT chunk too long");
+      return;
   }

   new_palette.nentries = (png_int_32)(data_length / entry_size);
@@ -1685,8 +1687,8 @@ png_handle_sPLT(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)

   if (new_palette.entries == NULL)
   {
-       png_warning(png_ptr, "sPLT chunk requires too much memory");
-       return;
+      png_warning(png_ptr, "sPLT chunk requires too much memory");
+      return;
   }

 #ifdef PNG_POINTER_INDEXING_SUPPORTED
@@ -2716,13 +2718,13 @@ png_cache_unknown_chunk(png_structrp png_ptr, png_uint_32 length)
   }

 #  ifdef PNG_SET_USER_LIMITS_SUPPORTED
-      if (png_ptr->user_chunk_malloc_max > 0 &&
-          png_ptr->user_chunk_malloc_max < limit)
-         limit = png_ptr->user_chunk_malloc_max;
+   if (png_ptr->user_chunk_malloc_max > 0 &&
+       png_ptr->user_chunk_malloc_max < limit)
+      limit = png_ptr->user_chunk_malloc_max;

 #  elif PNG_USER_CHUNK_MALLOC_MAX > 0
-      if (PNG_USER_CHUNK_MALLOC_MAX < limit)
-         limit = PNG_USER_CHUNK_MALLOC_MAX;
+   if (PNG_USER_CHUNK_MALLOC_MAX < limit)
+      limit = PNG_USER_CHUNK_MALLOC_MAX;
 #  endif

   if (length <= limit)
@@ -2785,7 +2787,7 @@ png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,
    */
 #  ifndef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
 #     ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
-         keep = png_chunk_unknown_handling(png_ptr, png_ptr->chunk_name);
+   keep = png_chunk_unknown_handling(png_ptr, png_ptr->chunk_name);
 #     endif
 #  endif

@@ -2794,153 +2796,153 @@ png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,
    * PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
    */
 #  ifdef PNG_READ_USER_CHUNKS_SUPPORTED
-      /* The user callback takes precedence over the chunk keep value, but the
-       * keep value is still required to validate a save of a critical chunk.
-       */
-      if (png_ptr->read_user_chunk_fn != NULL)
+   /* The user callback takes precedence over the chunk keep value, but the
+    * keep value is still required to validate a save of a critical chunk.
+    */
+   if (png_ptr->read_user_chunk_fn != NULL)
+   {
+      if (png_cache_unknown_chunk(png_ptr, length) != 0)
      {
-         if (png_cache_unknown_chunk(png_ptr, length) != 0)
+         /* Callback to user unknown chunk handler */
+         int ret = (*(png_ptr->read_user_chunk_fn))(png_ptr,
+            &png_ptr->unknown_chunk);
+
+         /* ret is:
+          * negative: An error occurred; png_chunk_error will be called.
+          *     zero: The chunk was not handled, the chunk will be discarded
+          *           unless png_set_keep_unknown_chunks has been used to set
+          *           a 'keep' behavior for this particular chunk, in which
+          *           case that will be used.  A critical chunk will cause an
+          *           error at this point unless it is to be saved.
+          * positive: The chunk was handled, libpng will ignore/discard it.
+          */
+         if (ret < 0)
+            png_chunk_error(png_ptr, "error in user chunk");
+
+         else if (ret == 0)
         {
-            /* Callback to user unknown chunk handler */
-            int ret = (*(png_ptr->read_user_chunk_fn))(png_ptr,
-               &png_ptr->unknown_chunk);
-
-            /* ret is:
-             * negative: An error occurred; png_chunk_error will be called.
-             *     zero: The chunk was not handled, the chunk will be discarded
-             *           unless png_set_keep_unknown_chunks has been used to set
-             *           a 'keep' behavior for this particular chunk, in which
-             *           case that will be used.  A critical chunk will cause an
-             *           error at this point unless it is to be saved.
-             * positive: The chunk was handled, libpng will ignore/discard it.
+            /* If the keep value is 'default' or 'never' override it, but
+             * still error out on critical chunks unless the keep value is
+             * 'always'  While this is weird it is the behavior in 1.4.12.
+             * A possible improvement would be to obey the value set for the
+             * chunk, but this would be an API change that would probably
+             * damage some applications.
+             *
+             * The png_app_warning below catches the case that matters, where
+             * the application has not set specific save or ignore for this
+             * chunk or global save or ignore.
             */
-            if (ret < 0)
-               png_chunk_error(png_ptr, "error in user chunk");
-
-            else if (ret == 0)
+            if (keep < PNG_HANDLE_CHUNK_IF_SAFE)
            {
-               /* If the keep value is 'default' or 'never' override it, but
-                * still error out on critical chunks unless the keep value is
-                * 'always'  While this is weird it is the behavior in 1.4.12.
-                * A possible improvement would be to obey the value set for the
-                * chunk, but this would be an API change that would probably
-                * damage some applications.
-                *
-                * The png_app_warning below catches the case that matters, where
-                * the application has not set specific save or ignore for this
-                * chunk or global save or ignore.
-                */
-               if (keep < PNG_HANDLE_CHUNK_IF_SAFE)
+#              ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
+               if (png_ptr->unknown_default < PNG_HANDLE_CHUNK_IF_SAFE)
               {
-#                 ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
-                     if (png_ptr->unknown_default < PNG_HANDLE_CHUNK_IF_SAFE)
-                     {
-                        png_chunk_warning(png_ptr, "Saving unknown chunk:");
-                        png_app_warning(png_ptr,
-                           "forcing save of an unhandled chunk;"
-                           " please call png_set_keep_unknown_chunks");
-                           /* with keep = PNG_HANDLE_CHUNK_IF_SAFE */
-                     }
-#                 endif
-                  keep = PNG_HANDLE_CHUNK_IF_SAFE;
+                  png_chunk_warning(png_ptr, "Saving unknown chunk:");
+                  png_app_warning(png_ptr,
+                     "forcing save of an unhandled chunk;"
+                     " please call png_set_keep_unknown_chunks");
+                     /* with keep = PNG_HANDLE_CHUNK_IF_SAFE */
               }
-            }
-
-            else /* chunk was handled */
-            {
-               handled = 1;
-               /* Critical chunks can be safely discarded at this point. */
-               keep = PNG_HANDLE_CHUNK_NEVER;
+#              endif
+               keep = PNG_HANDLE_CHUNK_IF_SAFE;
            }
         }

-         else
-            keep = PNG_HANDLE_CHUNK_NEVER; /* insufficient memory */
+         else /* chunk was handled */
+         {
+            handled = 1;
+            /* Critical chunks can be safely discarded at this point. */
+            keep = PNG_HANDLE_CHUNK_NEVER;
+         }
      }

      else
-         /* Use the SAVE_UNKNOWN_CHUNKS code or skip the chunk */
+         keep = PNG_HANDLE_CHUNK_NEVER; /* insufficient memory */
+   }
+
+   else
+   /* Use the SAVE_UNKNOWN_CHUNKS code or skip the chunk */
 #  endif /* READ_USER_CHUNKS */

 #  ifdef PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
+   {
+      /* keep is currently just the per-chunk setting, if there was no
+       * setting change it to the global default now (not that this may
+       * still be AS_DEFAULT) then obtain the cache of the chunk if required,
+       * if not simply skip the chunk.
+       */
+      if (keep == PNG_HANDLE_CHUNK_AS_DEFAULT)
+         keep = png_ptr->unknown_default;
+
+      if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
+         (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
+          PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
      {
-         /* keep is currently just the per-chunk setting, if there was no
-          * setting change it to the global default now (not that this may
-          * still be AS_DEFAULT) then obtain the cache of the chunk if required,
-          * if not simply skip the chunk.
-          */
-         if (keep == PNG_HANDLE_CHUNK_AS_DEFAULT)
-            keep = png_ptr->unknown_default;
-
-         if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
-            (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
-             PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
-         {
-            if (png_cache_unknown_chunk(png_ptr, length) == 0)
-               keep = PNG_HANDLE_CHUNK_NEVER;
-         }
-
-         else
-            png_crc_finish(png_ptr, length);
+         if (png_cache_unknown_chunk(png_ptr, length) == 0)
+            keep = PNG_HANDLE_CHUNK_NEVER;
      }
+
+      else
+         png_crc_finish(png_ptr, length);
+   }
 #  else
 #     ifndef PNG_READ_USER_CHUNKS_SUPPORTED
 #        error no method to support READ_UNKNOWN_CHUNKS
 #     endif

-      {
-         /* If here there is no read callback pointer set and no support is
-          * compiled in to just save the unknown chunks, so simply skip this
-          * chunk.  If 'keep' is something other than AS_DEFAULT or NEVER then
-          * the app has erroneously asked for unknown chunk saving when there
-          * is no support.
-          */
-         if (keep > PNG_HANDLE_CHUNK_NEVER)
-            png_app_error(png_ptr, "no unknown chunk support available");
+   {
+      /* If here there is no read callback pointer set and no support is
+       * compiled in to just save the unknown chunks, so simply skip this
+       * chunk.  If 'keep' is something other than AS_DEFAULT or NEVER then
+       * the app has erroneously asked for unknown chunk saving when there
+       * is no support.
+       */
+      if (keep > PNG_HANDLE_CHUNK_NEVER)
+         png_app_error(png_ptr, "no unknown chunk support available");

-         png_crc_finish(png_ptr, length);
-      }
+      png_crc_finish(png_ptr, length);
+   }
 #  endif

 #  ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
-      /* Now store the chunk in the chunk list if appropriate, and if the limits
-       * permit it.
-       */
-      if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
-         (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
-          PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
+   /* Now store the chunk in the chunk list if appropriate, and if the limits
+    * permit it.
+    */
+   if (keep == PNG_HANDLE_CHUNK_ALWAYS ||
+      (keep == PNG_HANDLE_CHUNK_IF_SAFE &&
+       PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)))
+   {
+#     ifdef PNG_USER_LIMITS_SUPPORTED
+      switch (png_ptr->user_chunk_cache_max)
      {
-#     ifdef PNG_USER_LIMITS_SUPPORTED
-         switch (png_ptr->user_chunk_cache_max)
-         {
-            case 2:
-               png_ptr->user_chunk_cache_max = 1;
-               png_chunk_benign_error(png_ptr, "no space in chunk cache");
-               /* FALL THROUGH */
-            case 1:
-               /* NOTE: prior to 1.6.0 this case resulted in an unknown critical
-                * chunk being skipped, now there will be a hard error below.
-                */
-               break;
+         case 2:
+            png_ptr->user_chunk_cache_max = 1;
+            png_chunk_benign_error(png_ptr, "no space in chunk cache");
+            /* FALL THROUGH */
+         case 1:
+            /* NOTE: prior to 1.6.0 this case resulted in an unknown critical
+             * chunk being skipped, now there will be a hard error below.
+             */
+            break;

-            default: /* not at limit */
-               --(png_ptr->user_chunk_cache_max);
-               /* FALL THROUGH */
-            case 0: /* no limit */
-#     endif /* USER_LIMITS */
-               /* Here when the limit isn't reached or when limits are compiled
-                * out; store the chunk.
-                */
-               png_set_unknown_chunks(png_ptr, info_ptr,
-                  &png_ptr->unknown_chunk, 1);
-               handled = 1;
-#     ifdef PNG_USER_LIMITS_SUPPORTED
-               break;
-         }
-#     endif
+         default: /* not at limit */
+            --(png_ptr->user_chunk_cache_max);
+            /* FALL THROUGH */
+         case 0: /* no limit */
+#  endif /* USER_LIMITS */
+            /* Here when the limit isn't reached or when limits are compiled
+             * out; store the chunk.
+             */
+            png_set_unknown_chunks(png_ptr, info_ptr,
+               &png_ptr->unknown_chunk, 1);
+            handled = 1;
+#  ifdef PNG_USER_LIMITS_SUPPORTED
+            break;
      }
+#  endif
+   }
 #  else /* no store support: the chunk must be handled by the user callback */
-      PNG_UNUSED(info_ptr)
+   PNG_UNUSED(info_ptr)
 #  endif

   /* Regardless of the error handling below the cached data (if any) can be
@@ -3042,13 +3044,13 @@ png_combine_row(png_const_structrp png_ptr, png_bytep dp, int display)
      end_ptr = dp + PNG_ROWBYTES(pixel_depth, row_width) - 1;
      end_byte = *end_ptr;
 #     ifdef PNG_READ_PACKSWAP_SUPPORTED
-         if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
-            /* little-endian byte */
-            end_mask = 0xff << end_mask;
+      if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
+         /* little-endian byte */
+         end_mask = 0xff << end_mask;

-         else /* big-endian byte */
+      else /* big-endian byte */
 #     endif
-         end_mask = 0xff >> end_mask;
+      end_mask = 0xff >> end_mask;
      /* end_mask is now the bits to *keep* from the destination row */
   }

@@ -3206,12 +3208,12 @@ png_combine_row(png_const_structrp png_ptr, png_bytep dp, int display)
         png_uint_32 mask;

 #        ifdef PNG_READ_PACKSWAP_SUPPORTED
-            if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
-               mask = MASK(pass, pixel_depth, display, 0);
+         if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
+            mask = MASK(pass, pixel_depth, display, 0);

-            else
+         else
 #        endif
-            mask = MASK(pass, pixel_depth, display, 1);
+         mask = MASK(pass, pixel_depth, display, 1);

         for (;;)
         {
@@ -3812,15 +3814,15 @@ png_read_filter_row_paeth_1byte_pixel(png_row_infop row_info, png_bytep row,
      p = b - c;
      pc = a - c;

-#     ifdef PNG_USE_ABS
-         pa = abs(p);
-         pb = abs(pc);
-         pc = abs(p + pc);
-#     else
-         pa = p < 0 ? -p : p;
-         pb = pc < 0 ? -pc : pc;
-         pc = (p + pc) < 0 ? -(p + pc) : p + pc;
-#     endif
+#ifdef PNG_USE_ABS
+      pa = abs(p);
+      pb = abs(pc);
+      pc = abs(p + pc);
+#else
+      pa = p < 0 ? -p : p;
+      pb = pc < 0 ? -pc : pc;
+      pc = (p + pc) < 0 ? -(p + pc) : p + pc;
+#endif

      /* Find the best predictor, the least of pa, pb, pc favoring the earlier
       * ones in the case of a tie.
@@ -3867,15 +3869,15 @@ png_read_filter_row_paeth_multibyte_pixel(png_row_infop row_info, png_bytep row,
      p = b - c;
      pc = a - c;

-#     ifdef PNG_USE_ABS
-         pa = abs(p);
-         pb = abs(pc);
-         pc = abs(p + pc);
-#     else
-         pa = p < 0 ? -p : p;
-         pb = pc < 0 ? -pc : pc;
-         pc = (p + pc) < 0 ? -(p + pc) : p + pc;
-#     endif
+#ifdef PNG_USE_ABS
+      pa = abs(p);
+      pb = abs(pc);
+      pc = abs(p + pc);
+#else
+      pa = p < 0 ? -p : p;
+      pb = pc < 0 ? -pc : pc;
+      pc = (p + pc) < 0 ? -(p + pc) : p + pc;
+#endif

      if (pb < pa) pa = pb, a = b;
      if (pc < pa) a = c;
@@ -4280,18 +4282,18 @@ png_read_start_row(png_structrp png_ptr)
 #ifdef PNG_READ_EXPAND_16_SUPPORTED
   if ((png_ptr->transformations & PNG_EXPAND_16) != 0)
   {
-#     ifdef PNG_READ_EXPAND_SUPPORTED
-         /* In fact it is an error if it isn't supported, but checking is
-          * the safe way.
-          */
-         if ((png_ptr->transformations & PNG_EXPAND) != 0)
-         {
-            if (png_ptr->bit_depth < 16)
-               max_pixel_depth *= 2;
-         }
-         else
-#     endif
-         png_ptr->transformations &= ~PNG_EXPAND_16;
+#  ifdef PNG_READ_EXPAND_SUPPORTED
+      /* In fact it is an error if it isn't supported, but checking is
+       * the safe way.
+       */
+      if ((png_ptr->transformations & PNG_EXPAND) != 0)
+      {
+         if (png_ptr->bit_depth < 16)
+            max_pixel_depth *= 2;
+      }
+      else
+#  endif
+      png_ptr->transformations &= ~PNG_EXPAND_16;
   }
 #endif

--- a/pngset.c
+++ b/pngset.c
@@ -1,7 +1,7 @@

 /* pngset.c - storage of image information into info struct
 *
- * Last changed in libpng 1.6.18 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 * Copyright (c) 1998-2015 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.)
--- a/pngstruct.h
+++ b/pngstruct.h
@@ -1,8 +1,8 @@

 /* pngstruct.h - header file for PNG reference library
 *
- * Last changed in libpng 1.6.1 [March 28, 2013]
- * Copyright (c) 1998-2013 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.18 [July 23, 2015]
+ * Copyright (c) 1998-2015 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.)
 *
@@ -219,16 +219,18 @@ struct png_struct_def
   png_uint_32 row_number;    /* current row in interlace pass */
   png_uint_32 chunk_name;    /* PNG_CHUNK() id of current chunk */
   png_bytep prev_row;        /* buffer to save previous (unfiltered) row.
-                               * This is a pointer into big_prev_row
+                               * While reading this is a pointer into
+                               * big_prev_row; while writing it is separately
+                               * allocated if needed.
                               */
   png_bytep row_buf;         /* buffer to save current (unfiltered) row.
-                               * This is a pointer into big_row_buf
+                               * While reading, this is a pointer into
+                               * big_row_buf; while writing it is separately
+                               * allocated.
                               */
-#ifdef PNG_WRITE_SUPPORTED
-   png_bytep sub_row;         /* buffer to save "sub" row when filtering */
-   png_bytep up_row;          /* buffer to save "up" row when filtering */
-   png_bytep avg_row;         /* buffer to save "avg" row when filtering */
-   png_bytep paeth_row;       /* buffer to save "Paeth" row when filtering */
+#ifdef PNG_WRITE_FILTER_SUPPORTED
+   png_bytep try_row;    /* buffer to save trial row when filtering */
+   png_bytep tst_row;    /* buffer to save best trial row when filtering */
 #endif
   png_size_t info_rowbytes;  /* Added in 1.5.4: cache of updated row bytes */

@@ -346,17 +348,7 @@ struct png_struct_def
   png_bytep quantize_index; /* index translation for palette files */
 #endif

-#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
-   png_byte heuristic_method;        /* heuristic for row filter selection */
-   png_byte num_prev_filters;        /* number of weights for previous rows */
-   png_bytep prev_filters;           /* filter type(s) of previous row(s) */
-   png_uint_16p filter_weights;      /* weight(s) for previous line(s) */
-   png_uint_16p inv_filter_weights;  /* 1/weight(s) for previous line(s) */
-   png_uint_16p filter_costs;        /* relative filter calculation cost */
-   png_uint_16p inv_filter_costs;    /* 1/relative filter calculation cost */
-#endif
-
-   /* Options */
+/* Options */
 #ifdef PNG_SET_OPTION_SUPPORTED
   png_byte options;           /* On/off state (up to 4 options) */
 #endif
--- a/pngtest.c
+++ b/pngtest.c
@@ -1,7 +1,7 @@

 /* pngtest.c - a simple test program to test libpng
 *
- * Last changed in libpng 1.6.18 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 * Copyright (c) 1998-2015 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.)
@@ -2028,4 +2028,4 @@ main(void)
 #endif

 /* Generate a compiler error if there is an old png.h in the search path. */
-typedef png_libpng_version_1_6_18beta04 Your_png_h_is_not_version_1_6_18beta04;
+typedef png_libpng_version_1_6_18 Your_png_h_is_not_version_1_6_18;
--- a/pngtrans.c
+++ b/pngtrans.c
@@ -1,7 +1,7 @@

 /* pngtrans.c - transforms the data in a row (used by both readers and writers)
 *
- * Last changed in libpng 1.6.18 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 * Copyright (c) 1998-2015 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.)
--- a/pngwrite.c
+++ b/pngwrite.c
@@ -1,7 +1,7 @@

 /* pngwrite.c - general routines to write a PNG file
 *
- * Last changed in libpng 1.6.17 [March 26, 2015]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 * Copyright (c) 1998-2015 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.)
@@ -90,43 +90,44 @@ png_write_info_before_PLTE(png_structrp png_ptr, png_const_inforp info_ptr)

   if ((png_ptr->mode & PNG_WROTE_INFO_BEFORE_PLTE) == 0)
   {
-   /* Write PNG signature */
-   png_write_sig(png_ptr);
+      /* Write PNG signature */
+      png_write_sig(png_ptr);

 #ifdef PNG_MNG_FEATURES_SUPPORTED
-   if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0 && \
-       png_ptr->mng_features_permitted != 0)
-   {
-      png_warning(png_ptr, "MNG features are not allowed in a PNG datastream");
-      png_ptr->mng_features_permitted = 0;
-   }
+      if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0 && \
+          png_ptr->mng_features_permitted != 0)
+      {
+         png_warning(png_ptr,
+             "MNG features are not allowed in a PNG datastream");
+         png_ptr->mng_features_permitted = 0;
+      }
 #endif

-   /* Write IHDR information. */
-   png_write_IHDR(png_ptr, info_ptr->width, info_ptr->height,
-       info_ptr->bit_depth, info_ptr->color_type, info_ptr->compression_type,
-       info_ptr->filter_type,
+      /* Write IHDR information. */
+      png_write_IHDR(png_ptr, info_ptr->width, info_ptr->height,
+          info_ptr->bit_depth, info_ptr->color_type, info_ptr->compression_type,
+          info_ptr->filter_type,
 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
-       info_ptr->interlace_type
+          info_ptr->interlace_type
 #else
-       0
+          0
 #endif
-      );
+         );

-   /* The rest of these check to see if the valid field has the appropriate
-    * flag set, and if it does, writes the chunk.
-    *
-    * 1.6.0: COLORSPACE support controls the writing of these chunks too, and
-    * the chunks will be written if the WRITE routine is there and information
-    * is available in the COLORSPACE.  (See png_colorspace_sync_info in png.c
-    * for where the valid flags get set.)
-    *
-    * Under certain circumstances the colorspace can be invalidated without
-    * syncing the info_struct 'valid' flags; this happens if libpng detects and
-    * error and calls png_error while the color space is being set, yet the
-    * application continues writing the PNG.  So check the 'invalid' flag here
-    * too.
-    */
+      /* The rest of these check to see if the valid field has the appropriate
+       * flag set, and if it does, writes the chunk.
+       *
+       * 1.6.0: COLORSPACE support controls the writing of these chunks too, and
+       * the chunks will be written if the WRITE routine is there and
+       * information * is available in the COLORSPACE. (See
+       * png_colorspace_sync_info in png.c for where the valid flags get set.)
+       *
+       * Under certain circumstances the colorspace can be invalidated without
+       * syncing the info_struct 'valid' flags; this happens if libpng detects
+       * an error and calls png_error while the color space is being set, yet
+       * the application continues writing the PNG.  So check the 'invalid'
+       * flag here too.
+       */
 #ifdef PNG_GAMMA_SUPPORTED
 #  ifdef PNG_WRITE_gAMA_SUPPORTED
      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
@@ -137,50 +138,50 @@ png_write_info_before_PLTE(png_structrp png_ptr, png_const_inforp info_ptr)
 #endif

 #ifdef PNG_COLORSPACE_SUPPORTED
-   /* Write only one of sRGB or an ICC profile.  If a profile was supplied
-    * and it matches one of the known sRGB ones issue a warning.
-    */
+      /* Write only one of sRGB or an ICC profile.  If a profile was supplied
+       * and it matches one of the known sRGB ones issue a warning.
+       */
 #  ifdef PNG_WRITE_iCCP_SUPPORTED
-      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
-          (info_ptr->valid & PNG_INFO_iCCP) != 0)
-      {
-#        ifdef PNG_WRITE_sRGB_SUPPORTED
-            if ((info_ptr->valid & PNG_INFO_sRGB) != 0)
-               png_app_warning(png_ptr,
-                  "profile matches sRGB but writing iCCP instead");
-#        endif
+         if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
+             (info_ptr->valid & PNG_INFO_iCCP) != 0)
+         {
+#    ifdef PNG_WRITE_sRGB_SUPPORTED
+               if ((info_ptr->valid & PNG_INFO_sRGB) != 0)
+                  png_app_warning(png_ptr,
+                     "profile matches sRGB but writing iCCP instead");
+#     endif

-         png_write_iCCP(png_ptr, info_ptr->iccp_name,
-            info_ptr->iccp_profile);
-      }
+            png_write_iCCP(png_ptr, info_ptr->iccp_name,
+               info_ptr->iccp_profile);
+         }
 #     ifdef PNG_WRITE_sRGB_SUPPORTED
         else
 #     endif
 #  endif

 #  ifdef PNG_WRITE_sRGB_SUPPORTED
-      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
-          (info_ptr->valid & PNG_INFO_sRGB) != 0)
-         png_write_sRGB(png_ptr, info_ptr->colorspace.rendering_intent);
+         if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
+             (info_ptr->valid & PNG_INFO_sRGB) != 0)
+            png_write_sRGB(png_ptr, info_ptr->colorspace.rendering_intent);
 #  endif /* WRITE_sRGB */
 #endif /* COLORSPACE */

 #ifdef PNG_WRITE_sBIT_SUPPORTED
-   if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
-      png_write_sBIT(png_ptr, &(info_ptr->sig_bit), info_ptr->color_type);
+         if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
+            png_write_sBIT(png_ptr, &(info_ptr->sig_bit), info_ptr->color_type);
 #endif

 #ifdef PNG_COLORSPACE_SUPPORTED
 #  ifdef PNG_WRITE_cHRM_SUPPORTED
-      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
-         (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) != 0 &&
-         (info_ptr->valid & PNG_INFO_cHRM) != 0)
-         png_write_cHRM_fixed(png_ptr, &info_ptr->colorspace.end_points_xy);
+         if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
+             (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) != 0 &&
+             (info_ptr->valid & PNG_INFO_cHRM) != 0)
+            png_write_cHRM_fixed(png_ptr, &info_ptr->colorspace.end_points_xy);
 #  endif
 #endif

 #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
-      write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_IHDR);
+         write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_IHDR);
 #endif

      png_ptr->mode |= PNG_WROTE_INFO_BEFORE_PLTE;
@@ -854,7 +855,7 @@ png_write_row(png_structrp png_ptr, png_const_bytep row)
    * which is also the output depth.
    */
   if (row_info.pixel_depth != png_ptr->pixel_depth ||
-      row_info.pixel_depth != png_ptr->transformed_pixel_depth)
+       row_info.pixel_depth != png_ptr->transformed_pixel_depth)
      png_error(png_ptr, "internal write transform logic error");

 #ifdef PNG_MNG_FEATURES_SUPPORTED
@@ -922,10 +923,6 @@ png_write_flush(png_structrp png_ptr)
 }
 #endif /* WRITE_FLUSH */

-#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
-static void png_reset_filter_heuristics(png_structrp png_ptr);/* forward decl */
-#endif
-
 /* Free any memory used in png_ptr struct without freeing the struct itself. */
 static void
 png_write_destroy(png_structrp png_ptr)
@@ -942,24 +939,11 @@ png_write_destroy(png_structrp png_ptr)
   png_ptr->row_buf = NULL;
 #ifdef PNG_WRITE_FILTER_SUPPORTED
   png_free(png_ptr, png_ptr->prev_row);
-   png_free(png_ptr, png_ptr->sub_row);
-   png_free(png_ptr, png_ptr->up_row);
-   png_free(png_ptr, png_ptr->avg_row);
-   png_free(png_ptr, png_ptr->paeth_row);
+   png_free(png_ptr, png_ptr->try_row);
+   png_free(png_ptr, png_ptr->tst_row);
   png_ptr->prev_row = NULL;
-   png_ptr->sub_row = NULL;
-   png_ptr->up_row = NULL;
-   png_ptr->avg_row = NULL;
-   png_ptr->paeth_row = NULL;
-#endif
-
-#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
-   /* Use this to save a little code space, it doesn't free the filter_costs */
-   png_reset_filter_heuristics(png_ptr);
-   png_free(png_ptr, png_ptr->filter_costs);
-   png_free(png_ptr, png_ptr->inv_filter_costs);
-   png_ptr->filter_costs = NULL;
-   png_ptr->inv_filter_costs = NULL;
+   png_ptr->try_row = NULL;
+   png_ptr->tst_row = NULL;
 #endif

 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
@@ -1049,6 +1033,7 @@ png_set_filter(png_structrp png_ptr, int method, int filters)
 #endif /* WRITE_FILTER */
      }

+#ifdef PNG_WRITE_FILTER_SUPPORTED
      /* If we have allocated the row_buf, this means we have already started
       * with the image and we should have allocated all of the filter buffers
       * that have been selected.  If prev_row isn't already allocated, then
@@ -1057,203 +1042,76 @@ png_set_filter(png_structrp png_ptr, int method, int filters)
       * wants to start and stop using particular filters during compression,
       * it should start out with all of the filters, and then remove them
       * or add them back after the start of compression.
+       *
+       * NOTE: this is a nasty constraint on the code, because it means that the
+       * prev_row buffer must be maintained even if there are currently no
+       * 'prev_row' requiring filters active.
       */
      if (png_ptr->row_buf != NULL)
      {
-#ifdef PNG_WRITE_FILTER_SUPPORTED
-         if ((png_ptr->do_filter & PNG_FILTER_SUB) != 0 &&
-             png_ptr->sub_row == NULL)
+         int num_filters;
+         png_alloc_size_t buf_size;
+
+         /* Repeat the checks in png_write_start_row; 1 pixel high or wide
+          * images cannot benefit from certain filters.  If this isn't done here
+          * the check below will fire on 1 pixel high images.
+          */
+         if (png_ptr->height == 1)
+            filters &= ~(PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH);
+
+         if (png_ptr->width == 1)
+            filters &= ~(PNG_FILTER_SUB|PNG_FILTER_AVG|PNG_FILTER_PAETH);
+
+         if ((filters & (PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH)) != 0
+            && png_ptr->prev_row == NULL)
         {
-            png_ptr->sub_row = (png_bytep)png_malloc(png_ptr,
-                (png_ptr->rowbytes + 1));
-            png_ptr->sub_row[0] = PNG_FILTER_VALUE_SUB;
+            /* This is the error case, however it is benign - the previous row
+             * is not available so the filter can't be used.  Just warn here.
+             */
+            png_app_warning(png_ptr,
+               "png_set_filter: UP/AVG/PAETH cannot be added after start");
+            filters &= ~(PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH);
         }

-         if ((png_ptr->do_filter & PNG_FILTER_UP) != 0 &&
-              png_ptr->up_row == NULL)
+         num_filters = 0;
+
+         if (filters & PNG_FILTER_SUB)
+            num_filters++;
+
+         if (filters & PNG_FILTER_UP)
+            num_filters++;
+
+         if (filters & PNG_FILTER_AVG)
+            num_filters++;
+
+         if (filters & PNG_FILTER_PAETH)
+            num_filters++;
+
+         /* Allocate needed row buffers if they have not already been
+          * allocated.
+          */
+         buf_size = PNG_ROWBYTES(png_ptr->usr_channels * png_ptr->usr_bit_depth,
+             png_ptr->width) + 1;
+
+         if (png_ptr->try_row == NULL)
+            png_ptr->try_row = png_voidcast(png_bytep,
+               png_malloc(png_ptr, buf_size));
+
+         if (num_filters > 1)
         {
-            if (png_ptr->prev_row == NULL)
-            {
-               png_warning(png_ptr, "Can't add Up filter after starting");
-               png_ptr->do_filter = (png_byte)(png_ptr->do_filter &
-                   ~PNG_FILTER_UP);
-            }
-
-            else
-            {
-               png_ptr->up_row = (png_bytep)png_malloc(png_ptr,
-                   (png_ptr->rowbytes + 1));
-               png_ptr->up_row[0] = PNG_FILTER_VALUE_UP;
-            }
+            if (png_ptr->tst_row == NULL)
+               png_ptr->tst_row = png_voidcast(png_bytep,
+                  png_malloc(png_ptr, buf_size));
         }
-
-         if ((png_ptr->do_filter & PNG_FILTER_AVG) != 0 &&
-              png_ptr->avg_row == NULL)
-         {
-            if (png_ptr->prev_row == NULL)
-            {
-               png_warning(png_ptr, "Can't add Average filter after starting");
-               png_ptr->do_filter = (png_byte)(png_ptr->do_filter &
-                   ~PNG_FILTER_AVG);
-            }
-
-            else
-            {
-               png_ptr->avg_row = (png_bytep)png_malloc(png_ptr,
-                   (png_ptr->rowbytes + 1));
-               png_ptr->avg_row[0] = PNG_FILTER_VALUE_AVG;
-            }
-         }
-
-         if ((png_ptr->do_filter & PNG_FILTER_PAETH) != 0 &&
-             png_ptr->paeth_row == NULL)
-         {
-            if (png_ptr->prev_row == NULL)
-            {
-               png_warning(png_ptr, "Can't add Paeth filter after starting");
-               png_ptr->do_filter &= (png_byte)(~PNG_FILTER_PAETH);
-            }
-
-            else
-            {
-               png_ptr->paeth_row = (png_bytep)png_malloc(png_ptr,
-                   (png_ptr->rowbytes + 1));
-               png_ptr->paeth_row[0] = PNG_FILTER_VALUE_PAETH;
-            }
-         }
-
-         if (png_ptr->do_filter == PNG_NO_FILTERS)
-#endif /* WRITE_FILTER */
-            png_ptr->do_filter = PNG_FILTER_NONE;
      }
+      png_ptr->do_filter = (png_byte)filters;
+#endif
   }
   else
      png_error(png_ptr, "Unknown custom filter method");
 }

-/* This allows us to influence the way in which libpng chooses the "best"
- * filter for the current scanline.  While the "minimum-sum-of-absolute-
- * differences metric is relatively fast and effective, there is some
- * question as to whether it can be improved upon by trying to keep the
- * filtered data going to zlib more consistent, hopefully resulting in
- * better compression.
- */
-#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED      /* GRR 970116 */
-/* Convenience reset API. */
-static void
-png_reset_filter_heuristics(png_structrp png_ptr)
-{
-   /* Clear out any old values in the 'weights' - this must be done because if
-    * the app calls set_filter_heuristics multiple times with different
-    * 'num_weights' values we would otherwise potentially have wrong sized
-    * arrays.
-    */
-   png_ptr->num_prev_filters = 0;
-   png_ptr->heuristic_method = PNG_FILTER_HEURISTIC_UNWEIGHTED;
-   if (png_ptr->prev_filters != NULL)
-   {
-      png_bytep old = png_ptr->prev_filters;
-      png_ptr->prev_filters = NULL;
-      png_free(png_ptr, old);
-   }
-   if (png_ptr->filter_weights != NULL)
-   {
-      png_uint_16p old = png_ptr->filter_weights;
-      png_ptr->filter_weights = NULL;
-      png_free(png_ptr, old);
-   }
-
-   if (png_ptr->inv_filter_weights != NULL)
-   {
-      png_uint_16p old = png_ptr->inv_filter_weights;
-      png_ptr->inv_filter_weights = NULL;
-      png_free(png_ptr, old);
-   }
-
-   /* Leave the filter_costs - this array is fixed size. */
-}
-
-static int
-png_init_filter_heuristics(png_structrp png_ptr, int heuristic_method,
-   int num_weights)
-{
-   if (png_ptr == NULL)
-      return 0;
-
-   /* Clear out the arrays */
-   png_reset_filter_heuristics(png_ptr);
-
-   /* Check arguments; the 'reset' function makes the correct settings for the
-    * unweighted case, but we must handle the weight case by initializing the
-    * arrays for the caller.
-    */
-   if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
-   {
-      int i;
-
-      if (num_weights > 0)
-      {
-         png_ptr->prev_filters = (png_bytep)png_malloc(png_ptr,
-             (png_uint_32)((sizeof (png_byte)) * num_weights));
-
-         /* To make sure that the weighting starts out fairly */
-         for (i = 0; i < num_weights; i++)
-         {
-            png_ptr->prev_filters[i] = 255;
-         }
-
-         png_ptr->filter_weights = (png_uint_16p)png_malloc(png_ptr,
-             (png_uint_32)((sizeof (png_uint_16)) * num_weights));
-
-         png_ptr->inv_filter_weights = (png_uint_16p)png_malloc(png_ptr,
-             (png_uint_32)((sizeof (png_uint_16)) * num_weights));
-
-         for (i = 0; i < num_weights; i++)
-         {
-            png_ptr->inv_filter_weights[i] =
-            png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
-         }
-
-         /* Safe to set this now */
-         png_ptr->num_prev_filters = (png_byte)num_weights;
-      }
-
-      /* If, in the future, there are other filter methods, this would
-       * need to be based on png_ptr->filter.
-       */
-      if (png_ptr->filter_costs == NULL)
-      {
-         png_ptr->filter_costs = (png_uint_16p)png_malloc(png_ptr,
-             (png_uint_32)((sizeof (png_uint_16)) * PNG_FILTER_VALUE_LAST));
-
-         png_ptr->inv_filter_costs = (png_uint_16p)png_malloc(png_ptr,
-             (png_uint_32)((sizeof (png_uint_16)) * PNG_FILTER_VALUE_LAST));
-      }
-
-      for (i = 0; i < PNG_FILTER_VALUE_LAST; i++)
-      {
-         png_ptr->inv_filter_costs[i] =
-         png_ptr->filter_costs[i] = PNG_COST_FACTOR;
-      }
-
-      /* All the arrays are inited, safe to set this: */
-      png_ptr->heuristic_method = PNG_FILTER_HEURISTIC_WEIGHTED;
-
-      /* Return the 'ok' code. */
-      return 1;
-   }
-   else if (heuristic_method == PNG_FILTER_HEURISTIC_DEFAULT ||
-      heuristic_method == PNG_FILTER_HEURISTIC_UNWEIGHTED)
-   {
-      return 1;
-   }
-   else
-   {
-      png_warning(png_ptr, "Unknown filter heuristic method");
-      return 0;
-   }
-}
-
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED /* DEPRECATED */
 /* Provide floating and fixed point APIs */
 #ifdef PNG_FLOATING_POINT_SUPPORTED
 void PNGAPI
@@ -1261,52 +1119,11 @@ png_set_filter_heuristics(png_structrp png_ptr, int heuristic_method,
    int num_weights, png_const_doublep filter_weights,
    png_const_doublep filter_costs)
 {
-   png_debug(1, "in png_set_filter_heuristics");
-
-   /* The internal API allocates all the arrays and ensures that the elements of
-    * those arrays are set to the default value.
-    */
-   if (png_init_filter_heuristics(png_ptr, heuristic_method, num_weights) == 0)
-      return;
-
-   /* If using the weighted method copy in the weights. */
-   if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
-   {
-      int i;
-      for (i = 0; i < num_weights; i++)
-      {
-         if (filter_weights[i] <= 0.0)
-         {
-            png_ptr->inv_filter_weights[i] =
-            png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
-         }
-
-         else
-         {
-            png_ptr->inv_filter_weights[i] =
-                (png_uint_16)(PNG_WEIGHT_FACTOR*filter_weights[i]+.5);
-
-            png_ptr->filter_weights[i] =
-                (png_uint_16)(PNG_WEIGHT_FACTOR/filter_weights[i]+.5);
-         }
-      }
-
-      /* Here is where we set the relative costs of the different filters.  We
-       * should take the desired compression level into account when setting
-       * the costs, so that Paeth, for instance, has a high relative cost at low
-       * compression levels, while it has a lower relative cost at higher
-       * compression settings.  The filter types are in order of increasing
-       * relative cost, so it would be possible to do this with an algorithm.
-       */
-      for (i = 0; i < PNG_FILTER_VALUE_LAST; i++) if (filter_costs[i] >= 1.0)
-      {
-         png_ptr->inv_filter_costs[i] =
-             (png_uint_16)(PNG_COST_FACTOR / filter_costs[i] + .5);
-
-         png_ptr->filter_costs[i] =
-             (png_uint_16)(PNG_COST_FACTOR * filter_costs[i] + .5);
-      }
-   }
+   PNG_UNUSED(png_ptr)
+   PNG_UNUSED(heuristic_method)
+   PNG_UNUSED(num_weights)
+   PNG_UNUSED(filter_weights)
+   PNG_UNUSED(filter_costs)
 }
 #endif /* FLOATING_POINT */

@@ -1316,63 +1133,11 @@ png_set_filter_heuristics_fixed(png_structrp png_ptr, int heuristic_method,
    int num_weights, png_const_fixed_point_p filter_weights,
    png_const_fixed_point_p filter_costs)
 {
-   png_debug(1, "in png_set_filter_heuristics_fixed");
-
-   /* The internal API allocates all the arrays and ensures that the elements of
-    * those arrays are set to the default value.
-    */
-   if (png_init_filter_heuristics(png_ptr, heuristic_method, num_weights) == 0)
-      return;
-
-   /* If using the weighted method copy in the weights. */
-   if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
-   {
-      int i;
-      for (i = 0; i < num_weights; i++)
-      {
-         if (filter_weights[i] <= 0)
-         {
-            png_ptr->inv_filter_weights[i] =
-            png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
-         }
-
-         else
-         {
-            png_ptr->inv_filter_weights[i] = (png_uint_16)
-               ((PNG_WEIGHT_FACTOR*filter_weights[i]+PNG_FP_HALF)/PNG_FP_1);
-
-            png_ptr->filter_weights[i] = (png_uint_16)((PNG_WEIGHT_FACTOR*
-               PNG_FP_1+(filter_weights[i]/2))/filter_weights[i]);
-         }
-      }
-
-      /* Here is where we set the relative costs of the different filters.  We
-       * should take the desired compression level into account when setting
-       * the costs, so that Paeth, for instance, has a high relative cost at low
-       * compression levels, while it has a lower relative cost at higher
-       * compression settings.  The filter types are in order of increasing
-       * relative cost, so it would be possible to do this with an algorithm.
-       */
-      for (i = 0; i < PNG_FILTER_VALUE_LAST; i++)
-         if (filter_costs[i] >= PNG_FP_1)
-      {
-         png_uint_32 tmp;
-
-         /* Use a 32 bit unsigned temporary here because otherwise the
-          * intermediate value will be a 32 bit *signed* integer (ANSI rules)
-          * and this will get the wrong answer on division.
-          */
-         tmp = PNG_COST_FACTOR*PNG_FP_1 + (filter_costs[i]/2);
-         tmp /= filter_costs[i];
-
-         png_ptr->inv_filter_costs[i] = (png_uint_16)tmp;
-
-         tmp = PNG_COST_FACTOR * filter_costs[i] + PNG_FP_HALF;
-         tmp /= PNG_FP_1;
-
-         png_ptr->filter_costs[i] = (png_uint_16)tmp;
-      }
-   }
+   PNG_UNUSED(png_ptr)
+   PNG_UNUSED(heuristic_method)
+   PNG_UNUSED(num_weights)
+   PNG_UNUSED(filter_weights)
+   PNG_UNUSED(filter_costs)
 }
 #endif /* FIXED_POINT */
 #endif /* WRITE_WEIGHTED_FILTER */
@@ -1621,14 +1386,14 @@ png_write_png(png_structrp png_ptr, png_inforp info_ptr,
    * alpha channel.
    */
   if ((transforms & (PNG_TRANSFORM_STRIP_FILLER_AFTER|
-      PNG_TRANSFORM_STRIP_FILLER_BEFORE)) != 0)
+       PNG_TRANSFORM_STRIP_FILLER_BEFORE)) != 0)
   {
 #ifdef PNG_WRITE_FILLER_SUPPORTED
      if ((transforms & PNG_TRANSFORM_STRIP_FILLER_AFTER) != 0)
      {
         if ((transforms & PNG_TRANSFORM_STRIP_FILLER_BEFORE) != 0)
            png_app_error(png_ptr,
-               "PNG_TRANSFORM_STRIP_FILLER: BEFORE+AFTER not supported");
+                "PNG_TRANSFORM_STRIP_FILLER: BEFORE+AFTER not supported");

         /* Continue if ignored - this is the pre-1.6.10 behavior */
         png_set_filler(png_ptr, 0, PNG_FILLER_AFTER);
@@ -1687,13 +1452,13 @@ png_write_png(png_structrp png_ptr, png_inforp info_ptr,


 #ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED
-#ifdef PNG_STDIO_SUPPORTED /* currently required for png_image_write_* */
+# ifdef PNG_STDIO_SUPPORTED /* currently required for png_image_write_* */
 /* Initialize the write structure - general purpose utility. */
 static int
 png_image_write_init(png_imagep image)
 {
   png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, image,
-          png_safe_error, png_safe_warning);
+       png_safe_error, png_safe_warning);

   if (png_ptr != NULL)
   {
@@ -1702,7 +1467,7 @@ png_image_write_init(png_imagep image)
      if (info_ptr != NULL)
      {
         png_controlp control = png_voidcast(png_controlp,
-            png_malloc_warn(png_ptr, (sizeof *control)));
+             png_malloc_warn(png_ptr, (sizeof *control)));

         if (control != NULL)
         {
@@ -1749,12 +1514,12 @@ static int
 png_write_image_16bit(png_voidp argument)
 {
   png_image_write_control *display = png_voidcast(png_image_write_control*,
-      argument);
+       argument);
   png_imagep image = display->image;
   png_structrp png_ptr = image->opaque->png_ptr;

   png_const_uint_16p input_row = png_voidcast(png_const_uint_16p,
-      display->first_row);
+       display->first_row);
   png_uint_16p output_row = png_voidcast(png_uint_16p, display->local_row);
   png_uint_16p row_end;
   const int channels = (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ? 3 : 1;
@@ -1763,17 +1528,18 @@ png_write_image_16bit(png_voidp argument)

   if ((image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
   {
-#     ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
-         if ((image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
-         {
-            aindex = -1;
-            ++input_row; /* To point to the first component */
-            ++output_row;
-         }
-
+#   ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
+      if ((image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
+      {
+         aindex = -1;
+         ++input_row; /* To point to the first component */
+         ++output_row;
+      }
         else
-#     endif
+            aindex = channels;
+#     else
         aindex = channels;
+#     endif
   }

   else
@@ -1855,7 +1621,7 @@ png_write_image_16bit(png_voidp argument)
 * calculation can be done to 15 bits of accuracy; however, the output needs to
 * be scaled in the range 0..255*65535, so include that scaling here.
 */
-#define UNP_RECIPROCAL(alpha) ((((0xffff*0xff)<<7)+(alpha>>1))/alpha)
+#   define UNP_RECIPROCAL(alpha) ((((0xffff*0xff)<<7)+(alpha>>1))/alpha)

 static png_byte
 png_unpremultiply(png_uint_32 component, png_uint_32 alpha,
@@ -1906,12 +1672,12 @@ static int
 png_write_image_8bit(png_voidp argument)
 {
   png_image_write_control *display = png_voidcast(png_image_write_control*,
-      argument);
+       argument);
   png_imagep image = display->image;
   png_structrp png_ptr = image->opaque->png_ptr;

   png_const_uint_16p input_row = png_voidcast(png_const_uint_16p,
-      display->first_row);
+       display->first_row);
   png_bytep output_row = png_voidcast(png_bytep, display->local_row);
   png_uint_32 y = image->height;
   const int channels = (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ? 3 : 1;
@@ -1921,17 +1687,17 @@ png_write_image_8bit(png_voidp argument)
      png_bytep row_end;
      int aindex;

-#     ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
-         if ((image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
-         {
-            aindex = -1;
-            ++input_row; /* To point to the first component */
-            ++output_row;
-         }
+#   ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
+      if ((image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
+      {
+         aindex = -1;
+         ++input_row; /* To point to the first component */
+         ++output_row;
+      }

-         else
-#     endif
-         aindex = channels;
+      else
+#   endif
+      aindex = channels;

      /* Use row_end in place of a loop counter: */
      row_end = output_row + image->width * (channels+1);
@@ -1965,7 +1731,7 @@ png_write_image_8bit(png_voidp argument)
         } /* while out_ptr < row_end */

         png_write_row(png_ptr, png_voidcast(png_const_bytep,
-            display->local_row));
+             display->local_row));
         input_row += display->row_bytes/(sizeof (png_uint_16));
      } /* while y */
   }
@@ -2004,25 +1770,25 @@ png_image_set_PLTE(png_image_write_control *display)
   const png_imagep image = display->image;
   const void *cmap = display->colormap;
   const int entries = image->colormap_entries > 256 ? 256 :
-      (int)image->colormap_entries;
+       (int)image->colormap_entries;

   /* NOTE: the caller must check for cmap != NULL and entries != 0 */
   const png_uint_32 format = image->format;
   const int channels = PNG_IMAGE_SAMPLE_CHANNELS(format);

-#  if defined(PNG_FORMAT_BGR_SUPPORTED) &&\
+#   if defined(PNG_FORMAT_BGR_SUPPORTED) &&\
      defined(PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED)
      const int afirst = (format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
-         (format & PNG_FORMAT_FLAG_ALPHA) != 0;
-#  else
+          (format & PNG_FORMAT_FLAG_ALPHA) != 0;
+#   else
 #     define afirst 0
-#  endif
+#   endif

-#  ifdef PNG_FORMAT_BGR_SUPPORTED
+#   ifdef PNG_FORMAT_BGR_SUPPORTED
      const int bgr = (format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
-#  else
+#   else
 #     define bgr 0
-#  endif
+#   endif

   int i, num_trans;
   png_color palette[256];
@@ -2047,11 +1813,11 @@ png_image_set_PLTE(png_image_write_control *display)
            if (channels >= 3) /* RGB */
            {
               palette[i].blue = (png_byte)PNG_sRGB_FROM_LINEAR(255 *
-                  entry[(2 ^ bgr)]);
+                   entry[(2 ^ bgr)]);
               palette[i].green = (png_byte)PNG_sRGB_FROM_LINEAR(255 *
-                  entry[1]);
+                   entry[1]);
               palette[i].red = (png_byte)PNG_sRGB_FROM_LINEAR(255 *
-                  entry[bgr]);
+                   entry[bgr]);
            }

            else /* Gray */
@@ -2127,12 +1893,12 @@ png_image_set_PLTE(png_image_write_control *display)
      }
   }

-#  ifdef afirst
+#   ifdef afirst
 #     undef afirst
-#  endif
-#  ifdef bgr
+#   endif
+#   ifdef bgr
 #     undef bgr
-#  endif
+#   endif

   png_set_PLTE(image->opaque->png_ptr, image->opaque->info_ptr, palette,
      entries);
@@ -2160,10 +1926,10 @@ png_image_write_main(png_voidp argument)
   int alpha = !colormap && (format & PNG_FORMAT_FLAG_ALPHA);
   int write_16bit = linear && !colormap && (display->convert_to_8bit == 0);

-#  ifdef PNG_BENIGN_ERRORS_SUPPORTED
+#   ifdef PNG_BENIGN_ERRORS_SUPPORTED
      /* Make sure we error out on any bad situation */
      png_set_benign_errors(png_ptr, 0/*error*/);
-#  endif
+#   endif

   /* Default the 'row_stride' parameter if required. */
   if (display->row_stride == 0)
@@ -2242,23 +2008,23 @@ png_image_write_main(png_voidp argument)
         png_set_swap(png_ptr);
   }

-#  ifdef PNG_SIMPLIFIED_WRITE_BGR_SUPPORTED
+#   ifdef PNG_SIMPLIFIED_WRITE_BGR_SUPPORTED
      if ((format & PNG_FORMAT_FLAG_BGR) != 0)
      {
         if (colormap == 0 && (format & PNG_FORMAT_FLAG_COLOR) != 0)
            png_set_bgr(png_ptr);
         format &= ~PNG_FORMAT_FLAG_BGR;
      }
-#  endif
+#   endif

-#  ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
+#   ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
      if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
      {
         if (colormap == 0 && (format & PNG_FORMAT_FLAG_ALPHA) != 0)
            png_set_swap_alpha(png_ptr);
         format &= ~PNG_FORMAT_FLAG_AFIRST;
      }
-#  endif
+#   endif

   /* If there are 16 or fewer color-map entries we wrote a lower bit depth
    * above, but the application data is still byte packed.
@@ -2294,9 +2060,9 @@ png_image_write_main(png_voidp argument)
       * it about 50 times.  The speed-up in pngstest was about 10-20% of the
       * total (user) time on a heavily loaded system.
       */
-#ifdef PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED
+#   ifdef PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED
      png_set_compression_level(png_ptr, 3);
-#endif
+#   endif
   }

   /* Check for the cases that currently require a pre-transform on the row
@@ -2459,6 +2225,6 @@ png_image_write_to_file(png_imagep image, const char *file_name,
   else
      return 0;
 }
-#endif /* STDIO */
+# endif /* STDIO */
 #endif /* SIMPLIFIED_WRITE */
 #endif /* WRITE */
--- a/pngwtran.c
+++ b/pngwtran.c
@@ -1,7 +1,7 @@

 /* pngwtran.c - transforms the data in a row for PNG writers
 *
- * Last changed in libpng 1.6.18 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.18 [July 23, 2015]
 * Copyright (c) 1998-2015 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.)
@@ -71,7 +71,8 @@ png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
         case 2:
         {
            png_bytep sp, dp;
-            int shift, v;
+            unsigned int shift;
+            int v;
            png_uint_32 i;
            png_uint_32 row_width = row_info->width;

@@ -110,7 +111,8 @@ png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
         case 4:
         {
            png_bytep sp, dp;
-            int shift, v;
+            unsigned int shift;
+            int v;
            png_uint_32 i;
            png_uint_32 row_width = row_info->width;

--- a/pngwutil.c
+++ b/pngwutil.c
--- a/projects/vstudio/readme.txt
+++ b/projects/vstudio/readme.txt
@@ -1,7 +1,7 @@

 VisualStudio instructions

-libpng version 1.6.18beta04 - May 20, 2015
+libpng version 1.6.18 - July 23, 2015

 Copyright (c) 1998-2010 Glenn Randers-Pehrson

--- a/projects/vstudio/zlib.props
+++ b/projects/vstudio/zlib.props
@@ -2,7 +2,7 @@
 <!--
 * zlib.props - location of zlib source
 *
- * libpng version 1.6.18beta04 - May 20, 2015
+ * libpng version 1.6.18 - July 23, 2015
 *
 * Copyright (c) 1998-2011 Glenn Randers-Pehrson
 *
--- a/scripts/README.txt
+++ b/scripts/README.txt
@@ -1,9 +1,9 @@

-Makefiles for  libpng version 1.6.18beta04 - May 20, 2015
+Makefiles for  libpng version 1.6.18 - July 23, 2015

 pnglibconf.h.prebuilt       =>  Stores configuration settings
 makefile.linux    =>  Linux/ELF makefile
-                       (gcc, creates libpng16.so.16.1.6.18beta04)
+                       (gcc, creates libpng16.so.16.1.6.18)
 makefile.gcc      =>  Generic makefile (gcc, creates static libpng.a)
 makefile.knr      =>  Archaic UNIX Makefile that converts files with
                       ansi2knr (Requires ansi2knr.c from
@@ -33,12 +33,12 @@ 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 libpng16.so.16.1.6.18beta04)
+                       creates libpng16.so.16.1.6.18)
 makefile.sgi      =>  Silicon Graphics IRIX makefile (cc, creates static lib)
 makefile.solaris  =>  Solaris 2.X makefile (gcc,
-                       creates libpng16.so.16.1.6.18beta04)
+                       creates libpng16.so.16.1.6.18)
 makefile.so9      =>  Solaris 9 makefile (gcc,
-                       creates libpng16.so.16.1.6.18beta04)
+                       creates libpng16.so.16.1.6.18)
 makefile.std      =>  Generic UNIX makefile (cc, creates static libpng.a)
 makefile.sunos    =>  Sun makefile
 makefile.32sunu   =>  Sun Ultra 32-bit makefile
--- a/scripts/def.c
+++ b/scripts/def.c
@@ -21,7 +21,7 @@ PNG_DFN "OS2 DESCRIPTION "PNG image compression library""
 PNG_DFN "OS2 CODE PRELOAD MOVEABLE DISCARDABLE"
 PNG_DFN ""
 PNG_DFN "EXPORTS"
-PNG_DFN ";Version 1.6.18beta04"
+PNG_DFN ";Version 1.6.18"

 #define PNG_EXPORTA(ordinal, type, name, args, attributes)\
        PNG_DFN "@" SYMBOL_PREFIX "@@" name "@"
--- a/scripts/libpng-config-head.in
+++ b/scripts/libpng-config-head.in
@@ -11,7 +11,7 @@

 # Modeled after libxml-config.

-version=1.6.18beta04
+version=1.6.18
 prefix=""
 libdir=""
 libs=""
--- a/scripts/libpng.pc.in
+++ b/scripts/libpng.pc.in
@@ -5,6 +5,6 @@ includedir=@includedir@/libpng16

 Name: libpng
 Description: Loads and saves PNG files
-Version: 1.6.18beta04
+Version: 1.6.18
 Libs: -L${libdir} -lpng16
 Cflags: -I${includedir}
--- a/scripts/makefile.ne12bsd
+++ b/scripts/makefile.ne12bsd
@@ -17,7 +17,7 @@ INCSDIR=${LOCALBASE}/include/libpng16

 LIB=	png16
 SHLIB_MAJOR=	0
-SHLIB_MINOR=	1.6.18beta04
+SHLIB_MINOR=	1.6.18
 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
--- a/scripts/makefile.netbsd
+++ b/scripts/makefile.netbsd
@@ -17,7 +17,7 @@ INCSDIR=${LOCALBASE}/include

 LIB=	png
 SHLIB_MAJOR=	16
-SHLIB_MINOR=	1.6.18beta04
+SHLIB_MINOR=	1.6.18
 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
--- a/scripts/makefile.openbsd
+++ b/scripts/makefile.openbsd
@@ -11,7 +11,7 @@ LIBDIR=	${PREFIX}/lib
 MANDIR= ${PREFIX}/man/cat

 SHLIB_MAJOR=	16
-SHLIB_MINOR=	1.6.18beta04
+SHLIB_MINOR=	1.6.18

 LIB=	png
 SRCS=	png.c pngerror.c pngget.c pngmem.c pngpread.c \
--- a/scripts/pnglibconf.dfa
+++ b/scripts/pnglibconf.dfa
@@ -222,7 +222,7 @@ option SET_OPTION disabled
 #                 with png_set_option
 # ARM_NEON_CHECK: (PNG_ARM_NEON == 1) compile a run-time check to see if Neon
 #                 extensions are supported. This is poorly supported and
-#                 deprectated - use the png_set_option API.
+#                 deprecated - use the png_set_option API.
 setting ARM_NEON_OPT
 option ARM_NEON_API disabled requires ALIGNED_MEMORY enables SET_OPTION,
   sets ARM_NEON_OPT 1
@@ -249,6 +249,17 @@ setting Z_DEFAULT_STRATEGY default @Z_FILTERED
 setting Z_DEFAULT_NOFILTER_STRATEGY default @Z_DEFAULT_STRATEGY
 setting ZLIB_VERNUM default @ZLIB_VERNUM

+# Linkage of:
+#
+#  API:      libpng API functions
+#  CALLBACK: internal non-file-local callbacks
+#  FUNCTION: internal non-file-local functions
+#  DATA:     internal non-file-local (const) data
+setting LINKAGE_API default extern
+setting LINKAGE_CALLBACK default extern
+setting LINKAGE_FUNCTION default extern
+setting LINKAGE_DATA default extern
+
 setting TEXT_Z_DEFAULT_COMPRESSION default @Z_DEFAULT_COMPRESSION
 setting TEXT_Z_DEFAULT_STRATEGY default @Z_DEFAULT_STRATEGY

--- a/scripts/pnglibconf.h.prebuilt
+++ b/scripts/pnglibconf.h.prebuilt
@@ -1,8 +1,8 @@
-/* libpng 1.6.18beta04 STANDARD API DEFINITION */
+/* libpng 1.6.18 STANDARD API DEFINITION */

 /* pnglibconf.h - library build configuration */

-/* Libpng version 1.6.18beta04 - May 20, 2015 */
+/* Libpng version 1.6.18 - July 23, 2015 */

 /* Copyright (c) 1998-2014 Glenn Randers-Pehrson */

@@ -190,6 +190,10 @@
 #define PNG_GAMMA_THRESHOLD_FIXED 5000
 #define PNG_IDAT_READ_SIZE PNG_ZBUF_SIZE
 #define PNG_INFLATE_BUF_SIZE 1024
+#define PNG_LINKAGE_API extern
+#define PNG_LINKAGE_CALLBACK extern
+#define PNG_LINKAGE_DATA extern
+#define PNG_LINKAGE_FUNCTION extern
 #define PNG_MAX_GAMMA_8 11
 #define PNG_QUANTIZE_BLUE_BITS 5
 #define PNG_QUANTIZE_GREEN_BITS 5
--- a/scripts/symbols.def
+++ b/scripts/symbols.def
@@ -1,4 +1,4 @@
-;Version 1.6.18beta04
+;Version 1.6.18
 ;--------------------------------------------------------------
 ; LIBPNG symbol list as a Win32 DEF file
 ; Contains all the symbols that can be exported from libpng