[master] Imported from libpng-1.6.17.tar

[master] Imported from libpng-1.6.16.tar
[master] Imported from libpng-1.6.15.tar
2025-07-10 18:04:09 +02:00 · 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 · 2014-08-21 05:59:56 -05:00
46 changed files with 1217 additions and 2505 deletions
--- a/102
+++ b/102
@@ -1,73 +1,67 @@
-Libpng 1.6.18beta06 - June 1, 2015
+Libpng 1.6.17 - March 26, 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

-   1.6.18beta06.tar.xz (LZMA-compressed, recommended)
-   1.6.18beta06.tar.gz
+   libpng-1.6.17.tar.xz (LZMA-compressed, recommended)
+   libpng-1.6.17.tar.gz

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

-   lp1618b06.7z  (LZMA-compressed, recommended)
-   lp1618b06.zip
+   lpng1617.7z  (LZMA-compressed, recommended)
+   lpng1617.zip

 Other information:

-   1.6.18beta06-README.txt
-   1.6.18beta06-LICENSE.txt
-   libpng-1.6.18beta06-*.asc (armored detached GPG signatures)
+   libpng-1.6.17-README.txt
+   libpng-1.6.17-LICENSE.txt
+   libpng-1.6.17-*.asc (armored detached GPG signatures)

-Changes since the last public release (1.6.17):
+Changes since the last public release (1.6.16):

-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).
-  Fixed rgb_to_gray checks and added tRNS checks to pngvalid.c.  This
-    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() (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.
+  Removed duplicate PNG_SAFE_LIMITS_SUPPORTED handling from pngconf.h
+  Corrected the width limit calculation in png_check_IHDR().
+  Removed user limits from pngfix. Also pass NULL pointers to
+    png_read_row to skip the unnecessary row de-interlace stuff.
+  Added testing of png_set_packing() to pngvalid.c
+  Regenerated configure scripts in the *.tar distributions with libtool-2.4.4
+  Implement previously untested cases of libpng transforms in pngvalid.c
+  Fixed byte order in 2-byte filler, in png_do_read_filler().
+  Made the check for out-of-range values in png_set_tRNS() detect
+    values that are exactly 2^bit_depth, and work on 16-bit platforms.
+  Merged some parts of libpng-1.6.17beta01 and libpng-1.7.0beta47.
+  Added #ifndef __COVERITY__ where needed in png.c, pngrutil.c and
+    pngset.c to avoid warnings about dead code.
+  Do not build png_product2() when it is unused.
+  Display user limits in the output from pngtest.
+  Eliminated the PNG_SAFE_LIMITS macro and restored the 1-million-column
+    and 1-million-row default limits in pnglibconf.dfa, that can be reset
+    by the user at build time or run time.  This provides a more robust
+    defense against DOS and as-yet undiscovered overflows.
+  Added PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED macro, on by default.
+  Allow user to call png_get_IHDR() with NULL arguments (Reuben Hawkins).
+  Rebuilt configure scripts with automake-1.15 and libtool-2.4.6
+  Moved png_set_filter() prototype into a PNG_WRITE_SUPPORTED block
+    of png.h.
+  Avoid runtime checks when converting integer to png_byte with
+    Visual Studio (Sergey Kosarevsky)
+  Removed some comments that the configure script did not handle
+    properly from scripts/pnglibconf.dfa and pnglibconf.h.prebuilt.
+  Free the unknown_chunks structure even when it contains no data.
+  Updated CMakeLists.txt to add OSX framework, change YES/NO to ON/OFF
+    for consistency, and remove some useless tests (Alexey Petruchik).
+  Remove pnglibconf.h, pnglibconf.c, pnglibconf.pre, pnglibconf.dfn,
+    and pnglibconf.out instead of pnglibconf.* in "make clean" (Cosmin).
+  Fixed simplified 8-bit-linear to sRGB alpha. The calculated alpha
+    value was wrong.  It's not clear if this affected the final stored
+    value; in the obvious code path the upper and lower 8-bits of the
+    alpha value were identical and the alpha was truncated to 8-bits
+    rather than dividing by 257 (John Bowler).

 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
--- a/76
+++ b/76
@@ -1,14 +1,11 @@
-#if 0
+
 CHANGES - changes for libpng

-version 0.1 [March 29, 1995]
-  initial work-in-progress release
-
-version 0.2 [April 1, 1995]
+Version 0.2
  added reader into png.h
  fixed small problems in stub file

-version 0.3 [April 8, 1995]
+Version 0.3
  added pull reader
  split up pngwrite.c to several files
  added pnglib.txt
@@ -17,9 +14,9 @@ version 0.3 [April 8, 1995]
  fixed some bugs in writer
  interfaced with zlib 0.5
  added K&R support
-  added check for 64 KB blocks for 16 bit machines
+  added check for 64 KB blocks for 16-bit machines

-version 0.4 [April 26, 1995]
+Version 0.4
  cleaned up code and commented code
  simplified time handling into png_time
  created png_color_16 and png_color_8 to handle color needs
@@ -30,29 +27,28 @@ version 0.4 [April 26, 1995]
  cleaned up zTXt reader and writer (using zlib's Reset functions)
  split transformations into pngrtran.c and pngwtran.c

-version 0.5 [April 30, 1995]
+Version 0.5
  interfaced with zlib 0.8
  fixed many reading and writing bugs
  saved using 3 spaces instead of tabs

-version 0.6 [May 1, 1995]
-  first beta release
+Version 0.6
  added png_large_malloc() and png_large_free()
  added png_size_t
  cleaned up some compiler warnings
  added png_start_read_image()

-version 0.7 [June 24, 1995]
+Version 0.7
  cleaned up lots of bugs
  finished dithering and other stuff
  added test program
  changed name from pnglib to libpng

-version 0.71 [June 26, 1995]
+Version 0.71 [June, 1995]
  changed pngtest.png for zlib 0.93
  fixed error in libpng.txt and example.c

-version 0.8 [August 20, 1995]
+Version 0.8
  cleaned up some bugs
  added png_set_filler()
  split up pngstub.c into pngmem.c, pngio.c, and pngerror.c
@@ -1453,9 +1449,8 @@ Version 1.2.6beta4 [July 28, 2004]
  Use png_malloc instead of png_zalloc to allocate the pallete.

 Version 1.0.16rc1 and 1.2.6rc1 [August 4, 2004]
-  Fixed buffer overflow vulnerability (CVE-2004-0597) in png_handle_tRNS().
-  Fixed NULL dereference vulnerability (CVE-2004-0598) in png_handle_iCCP().
-  Fixed integer overflow vulnerability (CVE-2004-0599) in png_read_png().
+  Fixed buffer overflow vulnerability in png_handle_tRNS()
+  Fixed integer arithmetic overflow vulnerability in png_read_png().
  Fixed some harmless bugs in png_handle_sBIT, etc, that would cause
    duplicate chunk types to go undetected.
  Fixed some timestamps in the -config version
@@ -5146,7 +5141,7 @@ Version 1.6.17beta01 [January 29, 2015]
  Added #ifndef __COVERITY__ where needed in png.c, pngrutil.c and
    pngset.c to avoid warnings about dead code.
  Added "& 0xff" to many instances of expressions that are typecast
-    to (png_byte), to avoid Coverity warnings.
+    to (png_byte), to avoid Coverity gripes.

 Version 1.6.17beta02 [February 7, 2015]
  Work around one more Coverity-scan dead-code warning.
@@ -5210,50 +5205,6 @@ Version 1.6.17rc06 [March 23, 2015]
 Version 1.6.17 [March 26, 2015]
  No changes.

-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).
-  Fixed rgb_to_gray checks and added tRNS checks to pngvalid.c.  This
-    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 PNG_DEBUG builds.
-  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.
-
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
@@ -5261,4 +5212,3 @@ to subscribe)
 or to glennrp at users.sourceforge.net

 Glenn R-P
-#endif
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -16,7 +16,7 @@ enable_testing()

 set(PNGLIB_MAJOR 1)
 set(PNGLIB_MINOR 6)
-set(PNGLIB_RELEASE 18)
+set(PNGLIB_RELEASE 17)
 set(PNGLIB_NAME libpng${PNGLIB_MAJOR}${PNGLIB_MINOR})
 set(PNGLIB_VERSION ${PNGLIB_MAJOR}.${PNGLIB_MINOR}.${PNGLIB_RELEASE})

@@ -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}.1.6.18beta06
+#   VERSION 16.${PNGLIB_RELEASE}.1.6.17
    VERSION 16.${PNGLIB_RELEASE}.0
    SOVERSION 16
    CLEAN_DIRECT_OUTPUT 1)
--- a/4
+++ b/4
@@ -10,7 +10,7 @@ this sentence.

 This code is released under the libpng license.

-libpng versions 1.2.6, August 15, 2004, through 1.6.18beta06, June 1, 2015, are
+libpng versions 1.2.6, August 15, 2004, through 1.6.17, March 26, 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
@@ -108,4 +108,4 @@ certification mark of the Open Source Initiative.

 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-June 1, 2015
+March 26, 2015
--- a/4
+++ b/4
@@ -1,4 +1,4 @@
-README for libpng version 1.6.18beta06 - June 1, 2015 (shared library 16.0)
+README for libpng version 1.6.17 - March 26, 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.
@@ -134,7 +134,7 @@ and ...".  If in doubt, send questions to me.  I'll bounce them
 to others, if necessary.

 Please do not send suggestions on how to change PNG.  We have
-been discussing PNG for twenty years now, and it is official and
+been discussing PNG for nineteen years now, and it is official and
 finished.  If you have suggestions for libpng, however, I'll
 gladly listen.  Even if your suggestion is not used immediately,
 it may be used later.
--- a/autogen.sh
+++ b/autogen.sh
@@ -73,9 +73,8 @@ done
 # present bad things are happening.
 #
 # The autotools generated files:
-libpng_autotools_files="Makefile.in aclocal.m4 config.guess config.h.in
-   config.h.in~ config.sub configure depcomp install-sh ltmain.sh missing\
-   test-driver"
+libpng_autotools_files="Makefile.in aclocal.m4 config.guess config.h.in\
+   config.sub configure depcomp install-sh ltmain.sh missing test-driver"
 #
 # Files generated by versions of configue >2.68 or automake >1.13 (i.e. later
 # versions than those required by configure.ac):
--- a/configure.ac
+++ b/configure.ac
@@ -18,7 +18,7 @@ AC_PREREQ([2.68])

 dnl Version number stuff here:

-AC_INIT([libpng],[1.6.18beta06],[png-mng-implement@lists.sourceforge.net])
+AC_INIT([libpng],[1.6.17],[png-mng-implement@lists.sourceforge.net])
 AC_CONFIG_MACRO_DIR([scripts])

 # libpng does not follow GNU file name conventions (hence 'foreign')
@@ -39,10 +39,10 @@ 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=1.6.18beta06
+PNGLIB_VERSION=1.6.17
 PNGLIB_MAJOR=1
 PNGLIB_MINOR=6
-PNGLIB_RELEASE=18
+PNGLIB_RELEASE=17

 dnl End of version number stuff

--- a/contrib/examples/simpleover.c
+++ b/contrib/examples/simpleover.c
@@ -1,645 +0,0 @@
-/*- simpleover
- *
- * COPYRIGHT: Written by John Cunningham Bowler, 2015.
- * To the extent possible under law, the author has waived all copyright and
- * related or neighboring rights to this work.  This work is published from:
- * United States.
- *
- * Read several PNG files, which should have an alpha channel or transparency
- * information, and composite them together to produce one or more 16-bit linear
- * RGBA intermediates.  This involves doing the correct 'over' composition to
- * combine the alpha channels and corresponding data.
- *
- * Finally read an output (background) PNG using the 24-bit RGB format (the
- * PNG will be composited on green (#00ff00) by default if it has an alpha
- * channel), and apply the intermediate image generated above to specified
- * locations in the image.
- *
- * The command line has the general format:
- *
- *    simpleover <background.png> [output.png]
- *        {--sprite=width,height,name {[--at=x,y] {sprite.png}}}
- *        {--add=name {x,y}}
- *
- * The --sprite and --add options may occur multiple times. They are executed
- * in order.  --add may refer to any sprite already read.
- *
- * This code is intended to show how to composite multiple images together
- * correctly.  Apart from the libpng Simplified API the only work done in here
- * is to combine multiple input PNG images into a single sprite; this involves
- * a Porter-Duff 'over' operation and the input PNG images may, as a result,
- * be regarded as being layered one on top of the other with the first (leftmost
- * on the command line) being at the bottom and the last on the top.
- */
-#include <stddef.h>
-#include <stdlib.h>
-#include <string.h>
-#include <stdio.h>
-#include <errno.h>
-
-/* Normally use <png.h> here to get the installed libpng, but this is done to
- * ensure the code picks up the local libpng implementation, so long as this
- * file is linked against a sufficiently recent libpng (1.6+) it is ok to
- * change this to <png.h>:
- */
-#include "../../png.h"
-
-#define sprite_name_chars 15
-struct sprite {
-   FILE         *file;
-   png_uint_16p  buffer;
-   unsigned int  width;
-   unsigned int  height;
-   char          name[sprite_name_chars+1];
-};
-
-#if 0 /* div by 65535 test program */
-#include <math.h>
-#include <stdio.h>
-
-int main(void) {
-   double err = 0;
-   unsigned int xerr = 0;
-   unsigned int r = 32769;
-   {
-      unsigned int x = 0;
-
-      do {
-         unsigned int t = x + (x >> 16) /*+ (x >> 31)*/ + r;
-         double v = x, errtest;
-
-         if (t < x) {
-            fprintf(stderr, "overflow: %u+%u -> %u\n", x, r, t);
-            return 1;
-         }
-
-         v /= 65535;
-         errtest = v;
-         t >>= 16;
-         errtest -= t;
-
-         if (errtest > err) {
-            err = errtest;
-            xerr = x;
-
-            if (errtest >= .5) {
-               fprintf(stderr, "error: %u/65535 = %f, not %u, error %f\n",
-                     x, v, t, errtest);
-               return 0;
-            }
-         }
-      } while (++x <= 65535U*65535U);
-   }
-
-   printf("error %f @ %u\n", err, xerr);
-
-   return 0;
-}
-#endif /* div by 65535 test program */
-
-static void
-sprite_op(const struct sprite *sprite, int x_offset, int y_offset,
-   png_imagep image, const png_uint_16 *buffer)
-{
-   /* This is where the Porter-Duff 'Over' operator is evaluated; change this
-    * code to change the operator (this could be parameterized).  Any other
-    * image processing operation could be used here.
-    */
-
-
-   /* Check for an x or y offset that pushes any part of the image beyond the
-    * right or bottom of the sprite:
-    */
-   if ((y_offset < 0 || (unsigned)/*SAFE*/y_offset < sprite->height) &&
-       (x_offset < 0 || (unsigned)/*SAFE*/x_offset < sprite->width))
-   {
-      unsigned int y = 0;
-
-      if (y_offset < 0)
-         y = -y_offset; /* Skip to first visible row */
-
-      do
-      {
-         unsigned int x = 0;
-
-         if (x_offset < 0)
-            x = -x_offset;
-
-         do
-         {
-            /* In and out are RGBA values, so: */
-            const png_uint_16 *in_pixel = buffer + (y * image->width + x)*4;
-            png_uint_32 in_alpha = in_pixel[3];
-
-            /* This is the optimized Porter-Duff 'Over' operation, when the
-             * input alpha is 0 the output is not changed.
-             */
-            if (in_alpha > 0) 
-            {
-               png_uint_16 *out_pixel = sprite->buffer +
-                  ((y+y_offset) * sprite->width + (x+x_offset))*4;
-
-               /* This is the weight to apply to the output: */
-               in_alpha = 65535-in_alpha;
-
-               if (in_alpha > 0)
-               {
-                  /* The input must be composed onto the output. This means
-                   * multiplying the current output pixel value by the inverse
-                   * of the input alpha (1-alpha). A division is required but
-                   * it is by the constant 65535.  Approximate this as:
-                   *
-                   *     (x + (x >> 16) + 32769) >> 16;
-                   *
-                   * This is exact (and does not overflow) for all values of
-                   * x in the range 0..65535*65535.  (Note that the calculation
-                   * produces the closest integer; the maximum error is <0.5).
-                   */
-                  png_uint_32 tmp;
-
-#                 define compose(c)\
-                     tmp = out_pixel[c] * in_alpha;\
-                     tmp = (tmp + (tmp >> 16) + 32769) >> 16;\
-                     out_pixel[c] = tmp + in_pixel[c]
-
-                  /* The following is very vectorizable... */
-                  compose(0);
-                  compose(1);
-                  compose(2);
-                  compose(3);
-               }
-
-               else
-                  out_pixel[0] = in_pixel[0],
-                  out_pixel[1] = in_pixel[1],
-                  out_pixel[2] = in_pixel[2],
-                  out_pixel[3] = in_pixel[3];
-            }
-         }
-         while (++x < image->width);
-      }
-      while (++y < image->height);
-   }
-}
-
-static int 
-create_sprite(struct sprite *sprite, int *argc, const char ***argv)
-{
-   /* Read the arguments and create this sprite. The sprite buffer has already
-    * been allocated. This reads the input PNGs one by one in linear format,
-    * composes them onto the sprite buffer (the code in the function above)
-    * then saves the result, converting it on the fly to PNG RGBA 8-bit format.
-    */
-   while (*argc > 0)
-   {
-      char tombstone;
-      int x = 0, y = 0;
-
-      if ((*argv)[0][0] == '-' && (*argv)[0][1] == '-')
-      {
-         /* The only supported option is --at. */
-         if (sscanf((*argv)[0], "--at=%d,%d%c", &x, &y, &tombstone) != 2)
-            break; /* success; caller will parse this option */
-
-         ++*argv, --*argc;
-      }
-
-      else
-      {
-         /* The argument has to be a file name */
-         png_image image;
-
-         image.version = PNG_IMAGE_VERSION;
-         image.opaque = NULL;
-
-         if (png_image_begin_read_from_file(&image, (*argv)[0]))
-         {
-            png_uint_16p buffer;
-
-            image.format = PNG_FORMAT_LINEAR_RGB_ALPHA;
-
-            buffer = malloc(PNG_IMAGE_SIZE(image));
-
-            if (buffer != NULL)
-            {
-               if (png_image_finish_read(&image, NULL/*background*/, buffer,
-                  0/*row_stride*/,
-                  NULL/*colormap for PNG_FORMAT_FLAG_COLORMAP*/))
-               {
-                  /* This is the place where the Porter-Duff 'Over' operator
-                   * needs to be done by this code.  In fact, any image
-                   * processing required can be done here; the data is in
-                   * the correct format (linear, 16-bit) and source and
-                   * destination are in memory.
-                   */
-                  sprite_op(sprite, x, y, &image, buffer);
-                  free(buffer);
-                  ++*argv, --*argc;
-                  /* And continue to the next argument */
-                  continue;
-               }
-
-               else
-               {
-                  free(buffer);
-                  fprintf(stderr, "simpleover: read %s: %s\n", (*argv)[0],
-                      image.message);
-               }
-            }
-
-            else
-            {
-               fprintf(stderr, "simpleover: out of memory: %lu bytes\n",
-                  (unsigned long)PNG_IMAGE_SIZE(image));
-
-               /* png_image_free must be called if we abort the Simplified API
-                * read because of a problem detected in this code.  If problems
-                * are detected in the Simplified API it cleans up itself.
-                */
-               png_image_free(&image);
-            }
-         }
-
-         else
-         {
-            /* Failed to read the first argument: */
-            fprintf(stderr, "simpleover: %s: %s\n", (*argv)[0], image.message);
-         }
-
-         return 0; /* failure */
-      }
-   }
-
-   /* All the sprite operations have completed successfully. Save the RGBA
-    * buffer as a PNG using the simplified write API.
-    */
-   sprite->file = tmpfile();
-
-   if (sprite->file != NULL)
-   {
-      png_image save;
-
-      memset(&save, 0, sizeof save);
-      save.version = PNG_IMAGE_VERSION;
-      save.opaque = NULL;
-      save.width = sprite->width;
-      save.height = sprite->height;
-      save.format = PNG_FORMAT_LINEAR_RGB_ALPHA;
-      save.flags = PNG_IMAGE_FLAG_FAST;
-      save.colormap_entries = 0;
-
-      if (png_image_write_to_stdio(&save, sprite->file, 1/*convert_to_8_bit*/,
-          sprite->buffer, 0/*row_stride*/, NULL/*colormap*/))
-      {
-         /* Success; the buffer is no longer needed: */
-         free(sprite->buffer);
-         sprite->buffer = NULL;
-         return 1; /* ok */
-      }
-
-      else
-         fprintf(stderr, "simpleover: write sprite %s: %s\n", sprite->name,
-            save.message);
-   }
-
-   else
-      fprintf(stderr, "simpleover: sprite %s: could not allocate tmpfile: %s\n",
-         sprite->name, strerror(errno));
-
-   return 0; /* fail */
-}
-
-static int
-add_sprite(png_imagep output, png_bytep out_buf, struct sprite *sprite,
-   int *argc, const char ***argv)
-{
-   /* Given a --add argument naming this sprite, perform the operations listed
-    * in the following arguments.  The arguments are expected to have the form
-    * (x,y), which is just an offset at which to add the sprite to the
-    * output.
-    */
-   while (*argc > 0)
-   {
-      char tombstone;
-      int x, y;
-
-      if ((*argv)[0][0] == '-' && (*argv)[0][1] == '-')
-         return 1; /* success */
-
-      if (sscanf((*argv)[0], "%d,%d%c", &x, &y, &tombstone) == 2)
-      {
-         /* Now add the new image into the sprite data, but only if it
-          * will fit.
-          */
-         if (x < 0 || y < 0 ||
-             (unsigned)/*SAFE*/x >= output->width ||
-             (unsigned)/*SAFE*/y >= output->height ||
-             sprite->width > output->width-x ||
-             sprite->height > output->height-y)
-         {
-            fprintf(stderr, "simpleover: sprite %s @ (%d,%d) outside image\n",
-               sprite->name, x, y);
-            /* Could just skip this, but for the moment it is an error */
-            return 0; /* error */
-         }
-
-         else
-         {
-            /* Since we know the sprite fits we can just read it into the
-             * output using the simplified API.
-             */
-            png_image in;
-
-            in.version = PNG_IMAGE_VERSION;
-            rewind(sprite->file);
-
-            if (png_image_begin_read_from_stdio(&in, sprite->file))
-            {
-               in.format = PNG_FORMAT_RGB; /* force compose */
-
-               if (png_image_finish_read(&in, NULL/*background*/,
-                  out_buf + (y*output->width + x)*3/*RGB*/,
-                  output->width*3/*row_stride*/,
-                  NULL/*colormap for PNG_FORMAT_FLAG_COLORMAP*/))
-               {
-                  ++*argv, --*argc;
-                  continue;
-               }
-            }
-
-            /* The read failed: */
-            fprintf(stderr, "simpleover: add sprite %s: %s\n", sprite->name,
-                in.message);
-            return 0; /* error */
-         }
-      }
-
-      else
-      {
-         fprintf(stderr, "simpleover: --add='%s': invalid position %s\n",
-               sprite->name, (*argv)[0]);
-         return 0; /* error */
-      }
-   }
-
-   return 1; /* ok */
-}
-
-static int
-simpleover_process(png_imagep output, png_bytep out_buf, int argc,
-   const char **argv)
-{
-   int result = 1; /* success */
-#  define csprites 10/*limit*/
-#  define str(a) #a
-   int nsprites = 0;
-   struct sprite sprites[csprites];
-
-   while (argc > 0)
-   {
-      result = 0; /* fail */
-
-      if (strncmp(argv[0], "--sprite=", 9) == 0)
-      {
-         char tombstone;
-
-         if (nsprites < csprites)
-         {
-            int n;
-
-            sprites[nsprites].width = sprites[nsprites].height = 0;
-            sprites[nsprites].name[0] = 0;
-
-            n = sscanf(argv[0], "--sprite=%u,%u,%" str(sprite_name_chars) "s%c",
-                &sprites[nsprites].width, &sprites[nsprites].height,
-                sprites[nsprites].name, &tombstone);
-            
-            if ((n == 2 || n == 3) &&
-                sprites[nsprites].width > 0 && sprites[nsprites].height > 0)
-            {
-               size_t buf_size, tmp;
-
-               /* Default a name if not given. */
-               if (sprites[nsprites].name[0] == 0)
-                  sprintf(sprites[nsprites].name, "sprite-%d", nsprites+1);
-
-               /* Allocate a buffer for the sprite and calculate the buffer
-                * size:
-                */
-               buf_size = sizeof (png_uint_16 [4]);
-               buf_size *= sprites[nsprites].width;
-               buf_size *= sprites[nsprites].height;
-
-               /* This can overflow a (size_t); check for this: */
-               tmp = buf_size;
-               tmp /= sprites[nsprites].width;
-               tmp /= sprites[nsprites].height;
-
-               if (tmp == sizeof (png_uint_16 [4]))
-               {
-                  sprites[nsprites].buffer = malloc(buf_size);
-                  /* This buffer must be initialized to transparent: */
-                  memset(sprites[nsprites].buffer, 0, buf_size);
-
-                  if (sprites[nsprites].buffer != NULL)
-                  {
-                     sprites[nsprites].file = NULL;
-                     ++argv, --argc;
-
-                     if (create_sprite(sprites+nsprites++, &argc, &argv))
-                     {
-                        result = 1; /* still ok */
-                        continue;
-                     }
-
-                     break; /* error */
-                  }
-               }
-
-               /* Overflow, or OOM */
-               fprintf(stderr, "simpleover: %s: sprite too large\n", argv[0]);
-               break;
-            }
-
-            else
-            {
-               fprintf(stderr, "simpleover: %s: invalid sprite (%u,%u)\n",
-                  argv[0], sprites[nsprites].width, sprites[nsprites].height);
-               break;
-            }
-         }
-
-         else
-         {
-            fprintf(stderr, "simpleover: %s: too many sprites\n", argv[0]);
-            break;
-         }
-      }
-
-      else if (strncmp(argv[0], "--add=", 6) == 0)
-      {
-         const char *name = argv[0]+6;
-         int isprite = nsprites;
-
-         ++argv, --argc;
-
-         while (--isprite >= 0)
-         {
-            if (strcmp(sprites[isprite].name, name) == 0)
-            {
-               if (!add_sprite(output, out_buf, sprites+isprite, &argc, &argv))
-                  goto out; /* error in add_sprite */
-
-               break; 
-            }
-         }
-
-         if (isprite < 0) /* sprite not found */
-         {
-            fprintf(stderr, "simpleover: --add='%s': sprite not found\n", name);
-            break;
-         }
-      }
-
-      else
-      {
-         fprintf(stderr, "simpleover: %s: unrecognized operation\n", argv[0]);
-         break;
-      }
-
-      result = 1; /* ok  */
-   }
-
-   /* Clean up the cache of sprites: */
-out:
-   while (--nsprites >= 0)
-   {
-      if (sprites[nsprites].buffer != NULL)
-         free(sprites[nsprites].buffer);
-
-      if (sprites[nsprites].file != NULL)
-         (void)fclose(sprites[nsprites].file);
-   }
-
-   return result;
-}
-
-int main(int argc, const char **argv)
-{
-   int result = 1; /* default to fail */
-
-   if (argc >= 2)
-   {
-      int argi = 2;
-      const char *output = NULL;
-      png_image image;
-
-      if (argc > 2 && argv[2][0] != '-'/*an operation*/)
-      {
-         output = argv[2];
-         argi = 3;
-      }
-
-      image.version = PNG_IMAGE_VERSION;
-      image.opaque = NULL;
-
-      if (png_image_begin_read_from_file(&image, argv[1]))
-      {
-         png_bytep buffer;
-
-         image.format = PNG_FORMAT_RGB; /* 24-bit RGB */
-
-         buffer = malloc(PNG_IMAGE_SIZE(image));
-
-         if (buffer != NULL)
-         {
-            png_color background = {0, 0xff, 0}; /* fully saturated green */
-
-            if (png_image_finish_read(&image, &background, buffer,
-               0/*row_stride*/, NULL/*colormap for PNG_FORMAT_FLAG_COLORMAP */))
-            {
-               /* At this point png_image_finish_read has cleaned up the
-                * allocated data in png_image, and only the buffer needs to be
-                * freed.
-                *
-                * Perform the remaining operations:
-                */
-               if (simpleover_process(&image, buffer, argc-argi, argv+argi))
-               {
-                  /* Write the output: */
-                  if ((output != NULL &&
-                       png_image_write_to_file(&image, output,
-                        0/*convert_to_8bit*/, buffer, 0/*row_stride*/,
-                        NULL/*colormap*/)) ||
-                      (output == NULL &&
-                       png_image_write_to_stdio(&image, stdout,
-                        0/*convert_to_8bit*/, buffer, 0/*row_stride*/,
-                        NULL/*colormap*/)))
-                     result = 0;
-
-                  else
-                     fprintf(stderr, "simpleover: write %s: %s\n",
-                        output == NULL ? "stdout" : output, image.message);
-               }
-
-               /* else simpleover_process writes an error message */
-            }
-
-            else
-               fprintf(stderr, "simpleover: read %s: %s\n", argv[1],
-                   image.message);
-
-            free(buffer);
-         }
-
-         else
-         {
-            fprintf(stderr, "simpleover: out of memory: %lu bytes\n",
-               (unsigned long)PNG_IMAGE_SIZE(image));
-
-            /* This is the only place where a 'free' is required; libpng does
-             * the cleanup on error and success, but in this case we couldn't
-             * complete the read because of running out of memory.
-             */
-            png_image_free(&image);
-         }
-      }
-
-      else
-      {
-         /* Failed to read the first argument: */
-         fprintf(stderr, "simpleover: %s: %s\n", argv[1], image.message);
-      }
-   }
-
-   else
-   {
-      /* Usage message */
-      fprintf(stderr,
-         "simpleover: usage: simpleover background.png [output.png]\n"
-         "  Output 'background.png' as a 24-bit RGB PNG file in 'output.png'\n"
-         "   or, if not given, stdout.  'background.png' will be composited\n"
-         "   on fully saturated green.\n"
-         "\n"
-         "  Optionally, before output, process additional PNG files:\n"
-         "\n"
-         "   --sprite=width,height,name {[--at=x,y] {sprite.png}}\n"
-         "    Produce a transparent sprite of size (width,height) and with\n"
-         "     name 'name'.\n"
-         "    For each sprite.png composite it using a Porter-Duff 'Over'\n"
-         "     operation at offset (x,y) in the sprite (defaulting to (0,0)).\n"
-         "     Input PNGs will be truncated to the area of the sprite.\n"
-         "\n"
-         "   --add='name' {x,y}\n"
-         "    Optionally, before output, composite a sprite, 'name', which\n"
-         "     must have been previously produced using --sprite, at each\n"
-         "     offset (x,y) in the output image.  Each sprite must fit\n"
-         "     completely within the output image.\n"
-         "\n"
-         "  PNG files are processed in the order they occur on the command\n"
-         "  line and thus the first PNG processed appears as the bottommost\n"
-         "  in the output image.\n");
-   }
-
-   return result;
-}
--- 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 1.6.17 [March 26, 2015]
 * Copyright (c) 2014-2015 Glenn Randers-Pehrson
 * Written by John Cunningham Bowler
 *
@@ -258,7 +258,7 @@ make_four_random_bytes(png_uint_32* seed, png_bytep bytes)
   make_random_bytes(seed, bytes, 4);
 }

-#if defined PNG_READ_SUPPORTED || defined PNG_WRITE_tRNS_SUPPORTED
+#ifdef PNG_READ_SUPPORTED
 static void
 randomize(void *pv, size_t size)
 {
@@ -267,9 +267,7 @@ randomize(void *pv, size_t size)
 }

 #define RANDOMIZE(this) randomize(&(this), sizeof (this))
-#endif /* READ || WRITE_tRNS */

-#ifdef PNG_READ_SUPPORTED
 static unsigned int
 random_mod(unsigned int max)
 {
@@ -297,8 +295,7 @@ random_choice(void)
 /* A numeric ID based on PNG file characteristics.  The 'do_interlace' field
 * simply records whether pngvalid did the interlace itself or whether it
 * was done by libpng.  Width and height must be less than 256.  'palette' is an
- * index of the palette to use for formats with a palette otherwise a boolean
- * indicating if a tRNS chunk was generated.
+ * index of the palette to use for formats with a palette (0 otherwise.)
 */
 #define FILEID(col, depth, palette, interlace, width, height, do_interlace) \
   ((png_uint_32)((col) + ((depth)<<3) + ((palette)<<8) + ((interlace)<<13) + \
@@ -319,16 +316,12 @@ standard_name(char *buffer, size_t bufsize, size_t pos, png_byte colour_type,
    png_uint_32 w, png_uint_32 h, int do_interlace)
 {
   pos = safecat(buffer, bufsize, pos, colour_types[colour_type]);
-   if (colour_type == 3) /* must have a palette */
+   if (npalette > 0)
   {
      pos = safecat(buffer, bufsize, pos, "[");
      pos = safecatn(buffer, bufsize, pos, npalette);
      pos = safecat(buffer, bufsize, pos, "]");
   }
-
-   else if (npalette != 0)
-      pos = safecat(buffer, bufsize, pos, "+tRNS");
-
   pos = safecat(buffer, bufsize, pos, " ");
   pos = safecatn(buffer, bufsize, pos, bit_depth);
   pos = safecat(buffer, bufsize, pos, " bit");
@@ -385,32 +378,25 @@ standard_name_from_id(char *buffer, size_t bufsize, size_t pos, png_uint_32 id)

 static int
 next_format(png_bytep colour_type, png_bytep bit_depth,
-   unsigned int* palette_number, int low_depth_gray, int tRNS)
+   unsigned int* palette_number, int no_low_depth_gray)
 {
   if (*bit_depth == 0)
   {
      *colour_type = 0;
-      if (low_depth_gray)
-         *bit_depth = 1;
-      else
+      if (no_low_depth_gray)
         *bit_depth = 8;
+      else
+         *bit_depth = 1;
      *palette_number = 0;
      return 1;
   }

-   if  (*colour_type < 4/*no alpha channel*/)
+   if (*colour_type == 3)
   {
-      /* Add multiple palettes for colour type 3, one image with tRNS
-       * and one without for other non-alpha formats:
-       */
-      unsigned int pn = ++*palette_number;
-      png_byte ct = *colour_type;
-
-      if (((ct == 0/*GRAY*/ || ct/*RGB*/ == 2) && tRNS && pn < 2) ||
-          (ct == 3/*PALETTE*/ && pn < PALETTE_COUNT(*bit_depth)))
+      /* Add multiple palettes for colour type 3. */
+      if (++*palette_number < PALETTE_COUNT(*bit_depth))
         return 1;

-      /* No: next bit depth */
      *palette_number = 0;
   }

@@ -1973,7 +1959,6 @@ typedef struct png_modifier

   /* Run tests on reading with a combination of transforms, */
   unsigned int             test_transform :1;
-   unsigned int             test_tRNS :1; /* Includes tRNS images */

   /* When to use the use_input_precision option, this controls the gamma
    * validation code checks.  If set any value that is within the transformed
@@ -2005,16 +1990,6 @@ typedef struct png_modifier
   unsigned int             test_gamma_expand16 :1;
   unsigned int             test_exhaustive :1;

-   /* Whether or not to run the low-bit-depth grayscale tests.  This fail on
-    * gamma images in some cases because of gross inaccuracies in the grayscale
-    * gamma handling for low bit depth.
-    */
-   unsigned int             test_lbg :1;
-   unsigned int             test_lbg_gamma_threshold :1;
-   unsigned int             test_lbg_gamma_transform :1;
-   unsigned int             test_lbg_gamma_sbit :1;
-   unsigned int             test_lbg_gamma_composition :1;
-
   unsigned int             log :1;   /* Log max error */

   /* Buffer information, the buffer size limits the size of the chunks that can
@@ -2067,11 +2042,6 @@ modifier_init(png_modifier *pm)
   pm->test_standard = 0;
   pm->test_size = 0;
   pm->test_transform = 0;
-#  ifdef PNG_WRITE_tRNS_SUPPORTED
-      pm->test_tRNS = 1;
-#  else
-      pm->test_tRNS = 0;
-#  endif
   pm->use_input_precision = 0;
   pm->use_input_precision_sbit = 0;
   pm->use_input_precision_16to8 = 0;
@@ -2084,11 +2054,6 @@ modifier_init(png_modifier *pm)
   pm->test_gamma_background = 0;
   pm->test_gamma_alpha_mode = 0;
   pm->test_gamma_expand16 = 0;
-   pm->test_lbg = 1;
-   pm->test_lbg_gamma_threshold = 1;
-   pm->test_lbg_gamma_transform = 1;
-   pm->test_lbg_gamma_sbit = 1;
-   pm->test_lbg_gamma_composition = 1;
   pm->test_exhaustive = 0;
   pm->log = 0;

@@ -3227,45 +3192,6 @@ init_standard_palette(png_store *ps, png_structp pp, png_infop pi, int npalette,
   }
 }

-#ifdef PNG_WRITE_tRNS_SUPPORTED
-static void
-set_random_tRNS(png_structp pp, png_infop pi, PNG_CONST png_byte colour_type,
-   PNG_CONST int bit_depth)
-{
-   /* To make this useful the tRNS color needs to match at least one pixel.
-    * Random values are fine for gray, including the 16-bit case where we know
-    * that the test image contains all the gray values.  For RGB we need more
-    * method as only 65536 different RGB values are generated.
-    */
-   png_color_16 tRNS;
-   const png_uint_16 mask = (png_uint_16)((1U << bit_depth)-1);
-
-   RANDOMIZE(tRNS);
-
-   if (colour_type & 2/*RGB*/)
-   {
-      if (bit_depth == 8)
-      {
-         tRNS.blue = tRNS.red ^ tRNS.green;
-         tRNS.red &= mask;
-         tRNS.green &= mask;
-         tRNS.blue &= mask;
-      }
-
-      else /* bit_depth == 16 */
-      {
-         tRNS.green = (png_uint_16)(tRNS.red * 257);
-         tRNS.blue = (png_uint_16)(tRNS.green * 17);
-      }
-   }
-
-   else
-      tRNS.gray &= mask;
-
-   png_set_tRNS(pp, pi, NULL, 0, &tRNS);
-}
-#endif
-
 /* The number of passes is related to the interlace type. There was no libpng
 * API to determine this prior to 1.5, so we need an inquiry function:
 */
@@ -3599,11 +3525,6 @@ make_transform_image(png_store* PNG_CONST ps, png_byte PNG_CONST colour_type,
      if (colour_type == 3) /* palette */
         init_standard_palette(ps, pp, pi, 1U << bit_depth, 1/*do tRNS*/);

-#     ifdef PNG_WRITE_tRNS_SUPPORTED
-         else if (palette_number)
-            set_random_tRNS(pp, pi, colour_type, bit_depth);
-#     endif
-
      png_write_info(pp, pi);

      if (png_get_rowbytes(pp, pi) !=
@@ -3677,20 +3598,19 @@ make_transform_image(png_store* PNG_CONST ps, png_byte PNG_CONST colour_type,
 }

 static void
-make_transform_images(png_modifier *pm)
+make_transform_images(png_store *ps)
 {
   png_byte colour_type = 0;
   png_byte bit_depth = 0;
   unsigned int palette_number = 0;

   /* This is in case of errors. */
-   safecat(pm->this.test, sizeof pm->this.test, 0, "make standard images");
+   safecat(ps->test, sizeof ps->test, 0, "make standard images");

   /* Use next_format to enumerate all the combinations we test, including
-    * generating multiple low bit depth palette images. Non-A images (palette
-    * and direct) are created with and without tRNS chunks.
+    * generating multiple low bit depth palette images.
    */
-   while (next_format(&colour_type, &bit_depth, &palette_number, 1, 1))
+   while (next_format(&colour_type, &bit_depth, &palette_number, 0))
   {
      int interlace_type;

@@ -3701,7 +3621,7 @@ make_transform_images(png_modifier *pm)

         standard_name(name, sizeof name, 0, colour_type, bit_depth,
            palette_number, interlace_type, 0, 0, 0);
-         make_transform_image(&pm->this, colour_type, bit_depth, palette_number,
+         make_transform_image(ps, colour_type, bit_depth, palette_number,
            interlace_type, name);
      }
   }
@@ -4367,7 +4287,6 @@ typedef struct standard_display
   size_t      cbRow;          /* Bytes in a row of the output image */
   int         do_interlace;   /* Do interlacing internally */
   int         is_transparent; /* Transparency information was present. */
-   int         has_tRNS;       /* color type GRAY or RGB with a tRNS chunk. */
   int         speed;          /* Doing a speed test */
   int         use_update_info;/* Call update_info, not start_image */
   struct
@@ -4700,14 +4619,14 @@ standard_info_part1(standard_display *dp, png_structp pp, png_infop pi)
         case 0:
            dp->transparent.red = dp->transparent.green = dp->transparent.blue =
               trans_color->gray;
-            dp->has_tRNS = 1;
+            dp->is_transparent = 1;
            break;

         case 2:
            dp->transparent.red = trans_color->red;
            dp->transparent.green = trans_color->green;
            dp->transparent.blue = trans_color->blue;
-            dp->has_tRNS = 1;
+            dp->is_transparent = 1;
            break;

         case 3:
@@ -5599,7 +5518,7 @@ image_pixel_add_alpha(image_pixel *this, PNG_CONST standard_display *display)
      if (this->colour_type == PNG_COLOR_TYPE_GRAY)
      {
         if (this->bit_depth < 8)
-            this->bit_depth = this->sample_depth = 8;
+            this->bit_depth = 8;

         if (this->have_tRNS)
         {
@@ -5634,11 +5553,9 @@ image_pixel_add_alpha(image_pixel *this, PNG_CONST standard_display *display)
               this->alphaf = 0;
            else
               this->alphaf = 1;
-         }
-         else
-            this->alphaf = 1;

-         this->colour_type = PNG_COLOR_TYPE_RGB_ALPHA;
+            this->colour_type = PNG_COLOR_TYPE_RGB_ALPHA;
+         }
      }

      /* The error in the alpha is zero and the sBIT value comes from the
@@ -5931,9 +5848,8 @@ transform_info_imp(transform_display *dp, png_structp pp, png_infop pi)
   /* If png_set_filler is in action then fake the output color type to include
    * an alpha channel where appropriate.
    */
-   if (dp->output_bit_depth >= 8 &&
-       (dp->output_colour_type == PNG_COLOR_TYPE_RGB ||
-        dp->output_colour_type == PNG_COLOR_TYPE_GRAY) && dp->this.filler)
+   if (dp->output_bit_depth >= 8 && (dp->output_colour_type == PNG_COLOR_TYPE_RGB ||
+       dp->output_colour_type == PNG_COLOR_TYPE_GRAY) && dp->this.filler)
       dp->output_colour_type |= 4;

   /* Validate the combination of colour type and bit depth that we are getting
@@ -6456,13 +6372,6 @@ image_transform_png_set_tRNS_to_alpha_set(PNG_CONST image_transform *this,
   transform_display *that, png_structp pp, png_infop pi)
 {
   png_set_tRNS_to_alpha(pp);
-
-   /* If there was a tRNS chunk that would get expanded and add an alpha
-    * channel is_transparent must be updated:
-    */
-   if (that->this.has_tRNS)
-      that->this.is_transparent = 1;
-
   this->next->set(this->next, that, pp, pi);
 }

@@ -6521,7 +6430,6 @@ image_transform_png_set_gray_to_rgb_set(PNG_CONST image_transform *this,
    transform_display *that, png_structp pp, png_infop pi)
 {
   png_set_gray_to_rgb(pp);
-   /* NOTE: this doesn't result in tRNS expansion. */
   this->next->set(this->next, that, pp, pi);
 }

@@ -6581,10 +6489,6 @@ image_transform_png_set_expand_set(PNG_CONST image_transform *this,
    transform_display *that, png_structp pp, png_infop pi)
 {
   png_set_expand(pp);
-
-   if (that->this.has_tRNS)
-      that->this.is_transparent = 1;
-
   this->next->set(this->next, that, pp, pi);
 }

@@ -6635,7 +6539,6 @@ image_transform_png_set_expand_gray_1_2_4_to_8_set(
    png_infop pi)
 {
   png_set_expand_gray_1_2_4_to_8(pp);
-   /* NOTE: don't expect this to expand tRNS */
   this->next->set(this->next, that, pp, pi);
 }

@@ -6667,11 +6570,6 @@ image_transform_png_set_expand_16_set(PNG_CONST image_transform *this,
    transform_display *that, png_structp pp, png_infop pi)
 {
   png_set_expand_16(pp);
-
-   /* NOTE: at present libpng does SET_EXPAND as well, so tRNS is expanded. */
-   if (that->this.has_tRNS)
-      that->this.is_transparent = 1;
-
   this->next->set(this->next, that, pp, pi);
 }

@@ -7042,14 +6940,14 @@ image_transform_png_set_rgb_to_gray_ini(PNG_CONST image_transform *this,
          * When DIGITIZE is set because a pre-1.7 version of libpng is being
          * tested allow a bigger slack.
          *
-          * NOTE: this magic number was determined by experiment to be about
-          * 1.263.  There's no great merit to the value below, however it only
-          * affects the limit used for checking for internal calculation errors,
-          * not the actual limit imposed by pngvalid on the output errors.
+          * NOTE: this magic number was determined by experiment to be 1.25.
+          * There's no great merit to the value below, however it only affects
+          * the limit used for checking for internal calculation errors, not
+          * the actual limit imposed by pngvalid on the output errors.
          */
         that->pm->limit += pow(
 #        if DIGITIZE
-            1.3
+            1.25
 #        else
            1.0
 #        endif
@@ -7213,8 +7111,7 @@ image_transform_png_set_rgb_to_gray_mod(PNG_CONST image_transform *this,
         const unsigned int sample_depth = that->sample_depth;
         const unsigned int calc_depth = (pm->assume_16_bit_calculations ? 16 :
            sample_depth);
-         const unsigned int gamma_depth = (sample_depth == 16 ?
-            PNG_MAX_GAMMA_8 :
+         const unsigned int gamma_depth = (sample_depth == 16 ? 16 :
            (pm->assume_16_bit_calculations ? PNG_MAX_GAMMA_8 : sample_depth));
         int isgray;
         double r, g, b;
@@ -7228,73 +7125,56 @@ image_transform_png_set_rgb_to_gray_mod(PNG_CONST image_transform *this,
          * will be identical after this operation if there is only one
          * transform, feel free to delete the png_error checks on this below in
          * the future (this is just me trying to ensure it works!)
-          *
-          * Interval arithmetic is exact, but to implement it it must be
-          * possible to control the floating point implementation rounding mode.
-          * This cannot be done in ANSI-C, so instead I reduce the 'lo' values
-          * by DBL_EPSILON and increase the 'hi' values by the same.
          */
-#        define DD(v,d,r) (digitize(v*(1-DBL_EPSILON), d, r) * (1-DBL_EPSILON))
-#        define DU(v,d,r) (digitize(v*(1+DBL_EPSILON), d, r) * (1+DBL_EPSILON))
-
         r = rlo = rhi = that->redf;
         rlo -= that->rede;
-         rlo = DD(rlo, calc_depth, 1/*round*/);
+         rlo = digitize(rlo, calc_depth, 1/*round*/);
         rhi += that->rede;
-         rhi = DU(rhi, calc_depth, 1/*round*/);
+         rhi = digitize(rhi, calc_depth, 1/*round*/);

         g = glo = ghi = that->greenf;
         glo -= that->greene;
-         glo = DD(glo, calc_depth, 1/*round*/);
+         glo = digitize(glo, calc_depth, 1/*round*/);
         ghi += that->greene;
-         ghi = DU(ghi, calc_depth, 1/*round*/);
+         ghi = digitize(ghi, calc_depth, 1/*round*/);

         b = blo = bhi = that->bluef;
         blo -= that->bluee;
-         blo = DD(blo, calc_depth, 1/*round*/);
+         blo = digitize(blo, calc_depth, 1/*round*/);
         bhi += that->greene;
-         bhi = DU(bhi, calc_depth, 1/*round*/);
+         bhi = digitize(bhi, calc_depth, 1/*round*/);

         isgray = r==g && g==b;

         if (data.gamma != 1)
         {
            PNG_CONST double power = 1/data.gamma;
-            PNG_CONST double abse = .5/(sample_depth == 16 ? 65535 : 255);
+            PNG_CONST double abse = calc_depth == 16 ? .5/65535 : .5/255;

-            /* If a gamma calculation is done it is done using lookup tables of
-             * precision gamma_depth, so the already digitized value above may
-             * need to be further digitized here.
+            /* 'abse' is the absolute error permitted in linear calculations. It
+             * is used here to capture the error permitted in the handling
+             * (undoing) of the gamma encoding.  Once again digitization occurs
+             * to handle the upper and lower bounds of the values.  This is
+             * where the real errors are introduced.
             */
-            if (gamma_depth != calc_depth)
-            {
-               rlo = DD(rlo, gamma_depth, 0/*truncate*/);
-               rhi = DU(rhi, gamma_depth, 0/*truncate*/);
-               glo = DD(glo, gamma_depth, 0/*truncate*/);
-               ghi = DU(ghi, gamma_depth, 0/*truncate*/);
-               blo = DD(blo, gamma_depth, 0/*truncate*/);
-               bhi = DU(bhi, gamma_depth, 0/*truncate*/);
-            }
-
-            /* 'abse' is the error in the gamma table calculation itself. */
            r = pow(r, power);
-            rlo = DD(pow(rlo, power)-abse, calc_depth, 1);
-            rhi = DU(pow(rhi, power)+abse, calc_depth, 1);
+            rlo = digitize(pow(rlo, power)-abse, calc_depth, 1);
+            rhi = digitize(pow(rhi, power)+abse, calc_depth, 1);

            g = pow(g, power);
-            glo = DD(pow(glo, power)-abse, calc_depth, 1);
-            ghi = DU(pow(ghi, power)+abse, calc_depth, 1);
+            glo = digitize(pow(glo, power)-abse, calc_depth, 1);
+            ghi = digitize(pow(ghi, power)+abse, calc_depth, 1);

            b = pow(b, power);
-            blo = DD(pow(blo, power)-abse, calc_depth, 1);
-            bhi = DU(pow(bhi, power)+abse, calc_depth, 1);
+            blo = digitize(pow(blo, power)-abse, calc_depth, 1);
+            bhi = digitize(pow(bhi, power)+abse, calc_depth, 1);
         }

         /* Now calculate the actual gray values.  Although the error in the
          * coefficients depends on whether they were specified on the command
          * line (in which case truncation to 15 bits happened) or not (rounding
          * was used) the maxium error in an individual coefficient is always
-          * 2/32768, because even in the rounding case the requirement that
+          * 1/32768, because even in the rounding case the requirement that
          * coefficients add up to 32768 can cause a larger rounding error.
          *
          * The only time when rounding doesn't occur in 1.5.5 and later is when
@@ -7305,19 +7185,19 @@ image_transform_png_set_rgb_to_gray_mod(PNG_CONST image_transform *this,

         {
            PNG_CONST int do_round = data.gamma != 1 || calc_depth == 16;
-            PNG_CONST double ce = 2. / 32768;
+            PNG_CONST double ce = 1. / 32768;

-            graylo = DD(rlo * (data.red_coefficient-ce) +
+            graylo = digitize(rlo * (data.red_coefficient-ce) +
               glo * (data.green_coefficient-ce) +
-               blo * (data.blue_coefficient-ce), calc_depth, do_round);
-            if (graylo > gray) /* always accept the right answer */
-               graylo = gray;
+               blo * (data.blue_coefficient-ce), gamma_depth, do_round);
+            if (graylo <= 0)
+               graylo = 0;

-            grayhi = DU(rhi * (data.red_coefficient+ce) +
+            grayhi = digitize(rhi * (data.red_coefficient+ce) +
               ghi * (data.green_coefficient+ce) +
-               bhi * (data.blue_coefficient+ce), calc_depth, do_round);
-            if (grayhi < gray)
-               grayhi = gray;
+               bhi * (data.blue_coefficient+ce), gamma_depth, do_round);
+            if (grayhi >= 1)
+               grayhi = 1;
         }

         /* And invert the gamma. */
@@ -7325,25 +7205,11 @@ image_transform_png_set_rgb_to_gray_mod(PNG_CONST image_transform *this,
         {
            PNG_CONST double power = data.gamma;

-            /* And this happens yet again, shifting the values once more. */
-            if (gamma_depth != sample_depth)
-            {
-               rlo = DD(rlo, gamma_depth, 0/*truncate*/);
-               rhi = DU(rhi, gamma_depth, 0/*truncate*/);
-               glo = DD(glo, gamma_depth, 0/*truncate*/);
-               ghi = DU(ghi, gamma_depth, 0/*truncate*/);
-               blo = DD(blo, gamma_depth, 0/*truncate*/);
-               bhi = DU(bhi, gamma_depth, 0/*truncate*/);
-            }
-
            gray = pow(gray, power);
-            graylo = DD(pow(graylo, power), sample_depth, 1);
-            grayhi = DU(pow(grayhi, power), sample_depth, 1);
+            graylo = digitize(pow(graylo, power), sample_depth, 1);
+            grayhi = digitize(pow(grayhi, power), sample_depth, 1);
         }

-#        undef DD
-#        undef DU
-
         /* Now the error can be calculated.
          *
          * If r==g==b because there is no overall gamma correction libpng
@@ -7394,28 +7260,16 @@ image_transform_png_set_rgb_to_gray_mod(PNG_CONST image_transform *this,
         {
            /* There is no need to do the conversions to and from linear space,
             * so the calculation should be a lot more accurate.  There is a
-             * built in error in the coefficients because they only have 15 bits
-             * and are adjusted to make sure they add up to 32768.  This
-             * involves a integer calculation with truncation of the form:
-             *
-             *     ((int)(coefficient * 100000) * 32768)/100000
-             *
-             * This is done to the red and green coefficients (the ones
-             * provided to the API) then blue is calculated from them so the
-             * result adds up to 32768.  In the worst case this can result in
-             * a -1 error in red and green and a +2 error in blue.  Consequently
-             * the worst case in the calculation below is 2/32768 error.
-             *
-             * TODO: consider fixing this in libpng by rounding the calculation
-             * limiting the error to 1/32768.
-             *
-             * Handling this by adding 2/32768 here avoids needing to increase
-             * the global error limits to take this into account.)
+             * built in 1/32768 error in the coefficients because they only have
+             * 15 bits and are adjusted to make sure they add up to 32768, so
+             * the result may have an additional error up to 1/32768.  (Note
+             * that adding the 1/32768 here avoids needing to increase the
+             * global error limits to take this into account.)
             */
            gray = r * data.red_coefficient + g * data.green_coefficient +
               b * data.blue_coefficient;
            err = re * data.red_coefficient + ge * data.green_coefficient +
-               be * data.blue_coefficient + 2./32768 + gray * 5 * DBL_EPSILON;
+               be * data.blue_coefficient + 1./32768 + gray * 5 * DBL_EPSILON;
         }

         else
@@ -7450,7 +7304,7 @@ image_transform_png_set_rgb_to_gray_mod(PNG_CONST image_transform *this,
             * previously added input quantization error at this point.
             */
            gray = r * data.red_coefficient + g * data.green_coefficient +
-               b * data.blue_coefficient - 2./32768 - out_qe;
+               b * data.blue_coefficient - 1./32768 - out_qe;
            if (gray <= 0)
               gray = 0;
            else
@@ -7460,7 +7314,7 @@ image_transform_png_set_rgb_to_gray_mod(PNG_CONST image_transform *this,
            }

            grayhi = rhi * data.red_coefficient + ghi * data.green_coefficient +
-               bhi * data.blue_coefficient + 2./32768 + out_qe;
+               bhi * data.blue_coefficient + 1./32768 + out_qe;
            grayhi *= (1 + 6 * DBL_EPSILON);
            if (grayhi >= 1)
               grayhi = 1;
@@ -7575,9 +7429,6 @@ image_transform_png_set_background_set(PNG_CONST image_transform *this,

   else
   {
-      if (that->this.has_tRNS)
-         that->this.is_transparent = 1;
-
      bit_depth = that->this.bit_depth;
      expand = 1;
   }
@@ -7655,13 +7506,13 @@ image_transform_png_set_background_mod(PNG_CONST image_transform *this,
      /* Remove the alpha type and set the alpha (not in that order.) */
      that->alphaf = 1;
      that->alphae = 0;
-   }

-   if (that->colour_type == PNG_COLOR_TYPE_RGB_ALPHA)
-      that->colour_type = PNG_COLOR_TYPE_RGB;
-   else if (that->colour_type == PNG_COLOR_TYPE_GRAY_ALPHA)
-      that->colour_type = PNG_COLOR_TYPE_GRAY;
-   /* PNG_COLOR_TYPE_PALETTE is not changed */
+      if (that->colour_type == PNG_COLOR_TYPE_RGB_ALPHA)
+         that->colour_type = PNG_COLOR_TYPE_RGB;
+      else if (that->colour_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+         that->colour_type = PNG_COLOR_TYPE_GRAY;
+      /* PNG_COLOR_TYPE_PALETTE is not changed */
+   }

   this->next->mod(this->next, that, pp, display);
 }
@@ -8450,8 +8301,7 @@ perform_transform_test(png_modifier *pm)
   png_byte bit_depth = 0;
   unsigned int palette_number = 0;

-   while (next_format(&colour_type, &bit_depth, &palette_number, pm->test_lbg,
-            pm->test_tRNS))
+   while (next_format(&colour_type, &bit_depth, &palette_number, 0))
   {
      png_uint_32 counter = 0;
      size_t base_pos;
@@ -8754,9 +8604,7 @@ init_validate_info(validate_info *vi, gamma_display *dp, png_const_structp pp,
   vi->outlog = outlog(dp->pm, in_depth, out_depth);

   if ((dp->this.colour_type & PNG_COLOR_MASK_ALPHA) != 0 ||
-      (dp->this.colour_type == 3 && dp->this.is_transparent) ||
-      ((dp->this.colour_type == 0 || dp->this.colour_type == 2) &&
-       dp->this.has_tRNS))
+      (dp->this.colour_type == 3 && dp->this.is_transparent))
   {
      vi->do_background = dp->do_background;

@@ -8786,7 +8634,7 @@ init_validate_info(validate_info *vi, gamma_display *dp, png_const_structp pp,
         vi->background_blue = b;
      }
   }
-   else /* Do not expect any background processing */
+   else
      vi->do_background = 0;

   if (vi->do_background == 0)
@@ -9502,7 +9350,6 @@ gamma_image_validate(gamma_display *dp, png_const_structp pp,
   png_uint_32 y;
   PNG_CONST store_palette_entry *in_palette = dp->this.palette;
   PNG_CONST int in_is_transparent = dp->this.is_transparent;
-   int process_tRNS;
   int out_npalette = -1;
   int out_is_transparent = 0; /* Just refers to the palette case */
   store_palette out_palette;
@@ -9518,7 +9365,6 @@ gamma_image_validate(gamma_display *dp, png_const_structp pp,

   processing = (vi.gamma_correction > 0 && !dp->threshold_test)
      || in_bd != out_bd || in_ct != out_ct || vi.do_background;
-   process_tRNS = dp->this.has_tRNS && vi.do_background;

   /* TODO: FIX THIS: MAJOR BUG!  If the transformations all happen inside
    * the palette there is no way of finding out, because libpng fails to
@@ -9557,8 +9403,8 @@ gamma_image_validate(gamma_display *dp, png_const_structp pp,
            /* Handle input alpha - png_set_background will cause the output
             * alpha to disappear so there is nothing to check.
             */
-            if ((in_ct & PNG_COLOR_MASK_ALPHA) != 0 ||
-                (in_ct == 3 && in_is_transparent))
+            if ((in_ct & PNG_COLOR_MASK_ALPHA) != 0 || (in_ct == 3 &&
+               in_is_transparent))
            {
               PNG_CONST unsigned int input_alpha = in_ct == 3 ?
                  dp->this.palette[in_index].alpha :
@@ -9590,35 +9436,6 @@ gamma_image_validate(gamma_display *dp, png_const_structp pp,
               }
            }

-            else if (process_tRNS)
-            {
-               /* alpha needs to be set appropriately for this pixel, it is
-                * currently 1 and needs to be 0 for an input pixel which matches
-                * the values in tRNS.
-                */
-               switch (in_ct)
-               {
-                  case 0: /* gray */
-                     if (sample(std, in_ct, in_bd, x, 0, 0, 0) ==
-                           dp->this.transparent.red)
-                        alpha = 0;
-                     break;
-
-                  case 2: /* RGB */
-                     if (sample(std, in_ct, in_bd, x, 0, 0, 0) ==
-                           dp->this.transparent.red &&
-                         sample(std, in_ct, in_bd, x, 1, 0, 0) ==
-                           dp->this.transparent.green &&
-                         sample(std, in_ct, in_bd, x, 2, 0, 0) ==
-                           dp->this.transparent.blue)
-                        alpha = 0;
-                     break;
-
-                  default:
-                     break;
-               }
-            }
-
            /* Handle grayscale or RGB components. */
            if ((in_ct & PNG_COLOR_MASK_COLOR) == 0) /* grayscale */
               (void)gamma_component_validate("gray", &vi,
@@ -9728,7 +9545,7 @@ gamma_test(png_modifier *pmIn, PNG_CONST png_byte colour_typeIn,

      modification_reset(d.pm->modifications);

-      /* Get a png_struct for reading the image. */
+      /* Get a png_struct for writing the image. */
      pp = set_modifier_for_read(d.pm, &pi, d.this.id, name);
      standard_palette_init(&d.this);

@@ -9867,13 +9684,9 @@ perform_gamma_threshold_tests(png_modifier *pm)
   /* Don't test more than one instance of each palette - it's pointless, in
    * fact this test is somewhat excessive since libpng doesn't make this
    * decision based on colour type or bit depth!
-    *
-    * CHANGED: now test two palettes and, as a side effect, images with and
-    * without tRNS.
    */
-   while (next_format(&colour_type, &bit_depth, &palette_number,
-                      pm->test_lbg_gamma_threshold, pm->test_tRNS))
-      if (palette_number < 2)
+   while (next_format(&colour_type, &bit_depth, &palette_number, 1/*gamma*/))
+      if (palette_number == 0)
   {
      double test_gamma = 1.0;
      while (test_gamma >= .4)
@@ -9933,8 +9746,7 @@ static void perform_gamma_transform_tests(png_modifier *pm)
   png_byte bit_depth = 0;
   unsigned int palette_number = 0;

-   while (next_format(&colour_type, &bit_depth, &palette_number,
-                      pm->test_lbg_gamma_transform, pm->test_tRNS))
+   while (next_format(&colour_type, &bit_depth, &palette_number, 1/*gamma*/))
   {
      unsigned int i, j;

@@ -9964,8 +9776,7 @@ static void perform_gamma_sbit_tests(png_modifier *pm)
      png_byte colour_type = 0, bit_depth = 0;
      unsigned int npalette = 0;

-      while (next_format(&colour_type, &bit_depth, &npalette,
-                         pm->test_lbg_gamma_sbit, pm->test_tRNS))
+      while (next_format(&colour_type, &bit_depth, &npalette, 1/*gamma*/))
         if ((colour_type & PNG_COLOR_MASK_ALPHA) == 0 &&
            ((colour_type == 3 && sbit < 8) ||
            (colour_type != 3 && sbit < bit_depth)))
@@ -10156,17 +9967,8 @@ static void gamma_composition_test(png_modifier *pm,
   }

   background.index = 193; /* rgb(193,193,193) to detect errors */
-
   if (!(colour_type & PNG_COLOR_MASK_COLOR))
   {
-      /* Because, currently, png_set_background is always called with
-       * 'need_expand' false in this case and because the gamma test itself
-       * doesn't cause an expand to 8-bit for lower bit depths the colour must
-       * be reduced to the correct range.
-       */
-      if (bit_depth < 8)
-         background.gray &= (png_uint_16)((1U << bit_depth)-1);
-
      /* Grayscale input, we do not convert to RGB (TBD), so we must set the
       * background to gray - else libpng seems to fail.
       */
@@ -10215,18 +10017,9 @@ perform_gamma_composition_tests(png_modifier *pm, int do_background,

   /* Skip the non-alpha cases - there is no setting of a transparency colour at
    * present.
-    *
-    * TODO: incorrect; the palette case sets tRNS and, now RGB and gray do,
-    * however the palette case fails miserably so is commented out below.
    */
-   while (next_format(&colour_type, &bit_depth, &palette_number,
-                      pm->test_lbg_gamma_composition, pm->test_tRNS))
-      if ((colour_type & PNG_COLOR_MASK_ALPHA) != 0
-#if 0 /* TODO: FIXME */
-          /*TODO: FIXME: this should work */
-          || colour_type == 3
-#endif
-          || (colour_type != 3 && palette_number != 0))
+   while (next_format(&colour_type, &bit_depth, &palette_number, 1/*gamma*/))
+      if ((colour_type & PNG_COLOR_MASK_ALPHA) != 0)
   {
      unsigned int i, j;

@@ -10958,18 +10751,6 @@ int main(int argc, char **argv)
   pm.ngammas = ARRAY_SIZE(gammas);
   pm.ngamma_tests = 0; /* default to off */

-   /* Low bit depth gray images don't do well in the gamma tests, until
-    * this is fixed turn them off for some gamma cases:
-    */
-#  ifdef PNG_WRITE_tRNS_SUPPORTED
-      pm.test_tRNS = 1;
-#  endif
-   pm.test_lbg = 0;
-   pm.test_lbg_gamma_threshold = 1;
-   pm.test_lbg_gamma_transform = 0/*PNG_LIBPNG_VER >= 10700*/;
-   pm.test_lbg_gamma_sbit = 1;
-   pm.test_lbg_gamma_composition = 0;
-
   /* And the test encodings */
   pm.encodings = test_encodings;
   pm.nencodings = ARRAY_SIZE(test_encodings);
@@ -11082,7 +10863,7 @@ int main(int argc, char **argv)
         pm.test_gamma_transform = 1;
         pm.test_gamma_sbit = 1;
         pm.test_gamma_scale16 = 1;
-         pm.test_gamma_background = 1; /* composition */
+         pm.test_gamma_background = 1;
         pm.test_gamma_alpha_mode = 1;
         }

@@ -11131,24 +10912,6 @@ int main(int argc, char **argv)
      else if (strcmp(*argv, "--noexpand16") == 0)
         pm.test_gamma_expand16 = 0;

-      else if (strcmp(*argv, "--low-depth-gray") == 0)
-         pm.test_lbg = pm.test_lbg_gamma_threshold =
-            pm.test_lbg_gamma_transform = pm.test_lbg_gamma_sbit =
-            pm.test_lbg_gamma_composition = 1;
-
-      else if (strcmp(*argv, "--nolow-depth-gray") == 0)
-         pm.test_lbg = pm.test_lbg_gamma_threshold =
-            pm.test_lbg_gamma_transform = pm.test_lbg_gamma_sbit =
-            pm.test_lbg_gamma_composition = 0;
-
-#     ifdef PNG_WRITE_tRNS_SUPPORTED
-         else if (strcmp(*argv, "--tRNS") == 0)
-            pm.test_tRNS = 1;
-#     endif
-
-      else if (strcmp(*argv, "--notRNS") == 0)
-         pm.test_tRNS = 0;
-
      else if (strcmp(*argv, "--more-gammas") == 0)
         pm.ngamma_tests = 3U;

@@ -11339,7 +11102,7 @@ int main(int argc, char **argv)
   Try
   {
      /* Make useful base images */
-      make_transform_images(&pm);
+      make_transform_images(&pm.this);

      /* Perform the standard and gamma tests. */
      if (pm.test_standard)
--- a/contrib/tools/genpng.c
+++ b/contrib/tools/genpng.c
@@ -1,864 +0,0 @@
-/*- genpng
- *
- * COPYRIGHT: Written by John Cunningham Bowler, 2015.
- * To the extent possible under law, the author has waived all copyright and
- * related or neighboring rights to this work.  This work is published from:
- * United States.
- *
- * Generate a PNG with an alpha channel, correctly.
- *
- * This is a test case generator; the resultant PNG files are only of interest
- * to those of us who care about whether the edges of circles are green, red,
- * or yellow.
- *
- * The program generates an RGB+Alpha PNG of a given size containing the given
- * shapes on a transparent background:
- *
- *  genpng width height { shape }
- *    shape ::= color width shape x1 y1 x2 y2
- *
- * 'color' is:
- *
- *  black white red green yellow blue brown purple pink orange gray cyan
- *
- * The point is to have colors that are linguistically meaningful plus that old
- * bugbear of the department store dress murders, Cyan, the only color we argue
- * about.
- *
- * 'shape' is:
- *
- *  circle: an ellipse
- *  square: a rectangle
- *  line: a straight line
- *
- * Each shape is followed by four numbers, these are two points in the output
- * coordinate space (as real numbers) which describe the circle, square, or
- * line.  The shape is filled if it is preceded by 'filled' (not valid for
- * 'line') or is drawn with a line, in which case the width of the line must
- * precede the shape.
- *
- * The whole set of information can be repeated as many times as desired:
- *
- *    shape ::= color width shape x1 y1 x2 y2
- *
- *    color ::= black|white|red|green|yellow|blue
- *    color ::= brown|purple|pink|orange|gray|cyan
- *    width ::= filled
- *    width ::= <number>
- *    shape ::= circle|square|line
- *    x1    ::= <number>
- *    x2    ::= <number>
- *    y1    ::= <number>
- *    y2    ::= <number>
- *
- * The output PNG is generated by down-sampling a 4x supersampled image using
- * a bi-cubic filter.  The bi-cubic has a 2 (output) pixel width, so an 8x8
- * array of super-sampled points contribute to each output pixel.  The value of
- * a super-sampled point is found using an unfiltered, aliased, infinite
- * precision image: Each shape from the last to the first is checked to see if
- * the point is in the drawn area and, if it is, the color of the point is the
- * color of the shape and the alpha is 1, if not the previous shape is checked.
- *
- * This is an aliased algorithm because no filtering is done; a point is either
- * inside or outside each shape and 'close' points do not contribute to the
- * sample.  The down-sampling is relied on to correct the error of not using
- * a filter.
- *
- * The line end-caps are 'flat'; they go through the points.  The square line
- * joins are mitres; the outside of the lines are continued to the point of
- * intersection.
- */
-#include <stddef.h>
-#include <stdlib.h>
-#include <string.h>
-#include <stdio.h>
-#include <math.h>
-
-/* Normally use <png.h> here to get the installed libpng, but this is done to
- * ensure the code picks up the local libpng implementation:
- */
-#include "../../png.h"
-
-static const struct color
-{
-   const char *name;
-   double      red;
-   double      green;
-   double      blue;
-} colors[] =
-/* color ::= black|white|red|green|yellow|blue
- * color ::= brown|purple|pink|orange|gray|cyan
- */
-{
-   { "black",   0,    0,  0 },
-   { "white",   1,    1,  1 },
-   { "red",     1,    0,  0 },
-   { "green",   0,    1,  0 },
-   { "yellow",  1,    1,  0 },
-   { "blue",    0,    0,  1 },
-   { "brown",  .5, .125,  0 },
-   { "purple",  1,    0,  1 },
-   { "pink",    1,   .5, .5 },
-   { "orange",  1,   .5,  0 },
-   { "gray",    0,   .5, .5 },
-   { "cyan",    0,    1,  1 }
-};
-#define color_count ((sizeof colors)/(sizeof colors[0]))
-
-static const struct color *
-color_of(const char *arg)
-{
-   int icolor = color_count;
-
-   while (--icolor >= 0)
-   {
-      if (strcmp(colors[icolor].name, arg) == 0)
-         return colors+icolor;
-   }
-
-   fprintf(stderr, "genpng: invalid color %s\n", arg);
-   exit(1);
-}
-
-static double
-width_of(const char *arg)
-{
-   if (strcmp(arg, "filled") == 0)
-      return 0;
-
-   else
-   {
-      char *ep = NULL;
-      double w = strtod(arg, &ep);
-
-      if (ep != NULL && *ep == 0 && w > 0)
-         return w;
-   }
-
-   fprintf(stderr, "genpng: invalid line width %s\n", arg);
-   exit(1);
-}
-
-static double
-coordinate_of(const char *arg)
-{
-   char *ep = NULL;
-   double w = strtod(arg, &ep);
-
-   if (ep != NULL && *ep == 0)
-      return w;
-
-   fprintf(stderr, "genpng: invalid coordinate value %s\n", arg);
-   exit(1);
-}
-
-struct arg; /* forward declaration */
-
-typedef int (*shape_fn_ptr)(const struct arg *arg, double x, double y);
-   /* A function to determine if (x,y) is inside the shape.
-    *
-    * There are two implementations:
-    *
-    *    inside_fn: returns true if the point is inside
-    *    check_fn:  returns;
-    *       -1: the point is outside the shape by more than the filter width (2)
-    *        0: the point may be inside the shape
-    *       +1: the point is inside the shape by more than the filter width
-    */
-#define OUTSIDE (-1)
-#define INSIDE  (1)
-
-struct arg
-{
-   const struct color *color;
-   shape_fn_ptr        inside_fn;
-   shape_fn_ptr        check_fn;
-   double              width; /* line width, 0 for 'filled' */
-   double              x1, y1, x2, y2;
-};
-
-/* IMPLEMENTATION NOTE:
- *
- * We want the contribution of each shape to the sample corresponding to each
- * pixel.  This could be obtained by super sampling the image to infinite
- * dimensions, finding each point within the shape and assigning that a value
- * '1' while leaving every point outside the shape with value '0' then
- * downsampling to the image size with sinc; computationally very expensive.
- *
- * Approximations are as follows:
- *
- * 1) If the pixel coordinate is within the shape assume the sample has the
- *    shape color and is opaque, else assume there is no contribution from
- *    the shape.
- *
- *    This is the equivalent of aliased rendering or resampling an image with
- *    a block filter.  The maximum error in the calculated alpha (which will
- *    always be 0 or 1) is 0.5.
- *
- * 2) If the shape is within a square of size 1x1 centered on the pixel assume
- *    that the shape obscures an amount of the pixel equal to its area within
- *    that square.
- *
- *    This is the equivalent of 'pixel coverage' alpha calculation or resampling
- *    an image with a bi-linear filter.  The maximum error is over 0.2, but the
- *    results are often acceptable.
- *
- *    This can be approximated by applying (1) to a super-sampled image then
- *    downsampling with a bi-linear filter.  The error in the super-sampled
- *    image is 0.5 per sample, but the resampling reduces this.
- *
- * 3) Use a better filter with a super-sampled image; in the limit this is the
- *    sinc() approach.
- *
- * 4) Do the geometric calculation; a bivariate definite integral across the
- *    shape, unfortunately this means evaluating Si(x), the integral of sinc(x),
- *    which is still a lot of math.
- *
- * This code uses approach (3) with a bi-cubic filter and 8x super-sampling
- * and method (1) for the super-samples.  This means that the sample is either
- * 0 or 1, depending on whether the sub-pixel is within or outside the shape.
- * The bi-cubic weights are also fixed and the 16 required weights are
- * pre-computed here (note that the 'scale' setting will need to be changed if
- * 'super' is increased).
- *
- * The code also calculates a sum to the edge of the filter. This is not
- * currently used by could be used to optimize the calculation.
- */
-#if 0 /* bc code */
-scale=10
-super=8
-define bicubic(x) {
-   if (x <= 1) return (1.5*x - 2.5)*x*x + 1;
-   if (x <  2) return (((2.5 - 0.5*x)*x - 4)*x + 2);
-   return 0;
-}
-define sum(x) {
-   auto s;
-   s = 0;
-   while (x < 2*super) {
-      s = s + bicubic(x/super);
-      x = x + 1;
-   }
-   return s;
-}
-define results(x) {
-   auto b, s;
-   b = bicubic(x/super);
-   s = sum(x);
-
-   print "   /*", x, "*/ { ", b, ", ", s, " }";
-   return 1;
-}
-x=0
-while (x<2*super) {
-   x = x + results(x)
-   if (x < 2*super) print ","
-   print "\n"
-}
-quit
-#endif
-
-#define BICUBIC1(x) /*     |x| <= 1 */ ((1.5*(x)* - 2.5)*(x)*(x) + 1)
-#define BICUBIC2(x) /* 1 < |x| <  2 */ (((2.5 - 0.5*(x))*(x) - 4)*(x) + 2)
-#define FILTER_WEIGHT 9 /* Twice the first sum below */
-#define FILTER_WIDTH  2 /* Actually half the width; -2..+2 */
-#define FILTER_STEPS  8 /* steps per filter unit */
-static const double
-bicubic[16][2] =
-{
-   /* These numbers are exact; the weight for the filter is 1/9, but this
-    * would make the numbers inexact, so it is not included here.
-    */
-   /*          bicubic      sum        */
-   /* 0*/ { 1.0000000000, 4.5000000000 },
-   /* 1*/ {  .9638671875, 3.5000000000 },
-   /* 2*/ {  .8671875000, 2.5361328125 },
-   /* 3*/ {  .7275390625, 1.6689453125 },
-   /* 4*/ {  .5625000000,  .9414062500 },
-   /* 5*/ {  .3896484375,  .3789062500 },
-   /* 6*/ {  .2265625000, -.0107421875 },
-   /* 7*/ {  .0908203125, -.2373046875 },
-   /* 8*/ {            0, -.3281250000 },
-   /* 9*/ { -.0478515625, -.3281250000 },
-   /*10*/ { -.0703125000, -.2802734375 },
-   /*11*/ { -.0732421875, -.2099609375 },
-   /*12*/ { -.0625000000, -.1367187500 },
-   /*13*/ { -.0439453125, -.0742187500 },
-   /*14*/ { -.0234375000, -.0302734375 },
-   /*15*/ { -.0068359375, -.0068359375 }
-};
-
-static double
-alpha_calc(const struct arg *arg, double x, double y)
-{
-   /* For [x-2..x+2],[y-2,y+2] calculate the weighted bicubic given a function
-    * which tells us whether a point is inside or outside the shape.  First
-    * check if we need to do this at all:
-    */
-   switch (arg->check_fn(arg, x, y))
-   {
-      case OUTSIDE:
-         return 0; /* all samples outside the shape */
-
-      case INSIDE:
-         return 1; /* all samples inside the shape */
-
-      default:
-      {
-         int dy;
-         double alpha = 0;
-
-#        define FILTER_D (FILTER_WIDTH*FILTER_STEPS-1)
-         for (dy=-FILTER_D; dy<=FILTER_D; ++dy)
-         {
-            double wy = bicubic[abs(dy)][0];
-
-            if (wy != 0)
-            {
-               double alphay = 0;
-               int dx;
-
-               for (dx=-FILTER_D; dx<=FILTER_D; ++dx)
-               {
-                  double wx = bicubic[abs(dx)][0];
-
-                  if (wx != 0 && arg->inside_fn(arg, x+dx/16, y+dy/16)) 
-                     alphay += wx;
-               }
-
-               alpha += wy * alphay;
-            }
-         }
-
-         /* This needs to be weighted for each dimension: */
-         return alpha / (FILTER_WEIGHT*FILTER_WEIGHT);
-      }
-   }
-}
-
-/* These are the shape functions. */
-/* "square",
- * { inside_square_filled, check_square_filled },
- * { inside_square, check_square }
- */
-static int
-square_check(double x, double y, double x1, double y1, double x2, double y2)
-   /* Is x,y inside the square (x1,y1)..(x2,y2)? */
-{
-   /* Do a modified Cohen-Sutherland on one point, bit patterns that indicate
-    * 'outside' are:
-    *
-    *   x<x1 | x<y1 | x<x2 | x<y2
-    *    0      x      0      x     To the right
-    *    1      x      1      x     To the left
-    *    x      0      x      0     Below
-    *    x      1      x      1     Above
-    *
-    * So 'inside' is (x<x1) != (x<x2) && (y<y1) != (y<y2);
-    */
-   return ((x<x1) ^ (x<x2)) & ((y<y1) ^ (y<y2));
-}
-
-static int
-inside_square_filled(const struct arg *arg, double x, double y)
-{
-   return square_check(x, y, arg->x1, arg->y1, arg->x2, arg->y2);
-}
-
-static int
-square_check_line(const struct arg *arg, double x, double y, double w)
-   /* Check for a point being inside the boundaries implied by the given arg
-    * and assuming a width 2*w each side of the boundaries.  This returns the
-    * 'check' INSIDE/OUTSIDE/0 result but note the semantics:
-    *
-    *          +--------------+
-    *          |              |   OUTSIDE
-    *          |   INSIDE     |
-    *          |              |
-    *          +--------------+
-    *
-    * And '0' means within the line boundaries.
-    */
-{
-   double cx = (arg->x1+arg->x2)/2;
-   double wx = fabs(arg->x1-arg->x2)/2;
-   double cy = (arg->y1+arg->y2)/2;
-   double wy = fabs(arg->y1-arg->y2)/2;
-
-   if (square_check(x, y, cx-wx-w, cy-wy-w, cx+wx+w, cy+wy+w))
-   {
-      /* Inside, but maybe too far; check for the redundant case where
-       * the lines overlap:
-       */
-      wx -= w;
-      wy -= w;
-      if (wx > 0 && wy > 0 && square_check(x, y, cx-wx, cy-wy, cx+wx, cy+wy))
-         return INSIDE; /* between (inside) the boundary lines. */
-
-      return 0; /* inside the lines themselves. */
-   }
-
-   return OUTSIDE; /* outside the boundary lines. */
-}
-
-static int
-check_square_filled(const struct arg *arg, double x, double y)
-{
-   /* The filter extends +/-FILTER_WIDTH each side of each output point, so
-    * the check has to expand and contract the square by that amount; '0'
-    * means close enough to the edge of the square that the bicubic filter has
-    * to be run, OUTSIDE means alpha==0, INSIDE means alpha==1.
-    */
-   return square_check_line(arg, x, y, FILTER_WIDTH);
-}
-
-static int
-inside_square(const struct arg *arg, double x, double y)
-{
-   /* Return true if within the drawn lines, else false, no need to distinguish
-    * INSIDE vs OUTSIDE here:
-    */
-   return square_check_line(arg, x, y, arg->width/2) == 0;
-}
-
-static int
-check_square(const struct arg *arg, double x, double y)
-{
-   /* So for this function a result of 'INSIDE' means inside the actual lines.
-    */
-   double w = arg->width/2;
-
-   if (square_check_line(arg, x, y, w+FILTER_WIDTH) == 0)
-   {
-      /* Somewhere close to the boundary lines. If far enough inside one of
-       * them then we can return INSIDE:
-       */
-      w -= FILTER_WIDTH;
-
-      if (w > 0 && square_check_line(arg, x, y, w) == 0)
-         return INSIDE;
-
-      /* Point is somewhere in the filter region: */
-      return 0;
-   }
-
-   else /* Inside or outside the square by more than w+FILTER_WIDTH. */
-      return OUTSIDE;
-}
-
-/* "circle",
- * { inside_circle_filled, check_circle_filled },
- * { inside_circle, check_circle }
- *
- * The functions here are analoguous to the square ones; however, they check
- * the corresponding ellipse as opposed to the rectangle.
- */
-static int
-circle_check(double x, double y, double x1, double y1, double x2, double y2)
-{
-   if (square_check(x, y, x1, y1, x2, y2))
-   {
-      /* Inside the square, so maybe inside the circle too: */
-      const double cx = (x1 + x2)/2;
-      const double cy = (y1 + y2)/2;
-      const double dx = x1 - x2;
-      const double dy = y1 - y2;
-
-      x = (x - cx)/dx;
-      y = (y - cy)/dy;
-
-      /* It is outside if the distance from the center is more than half the
-       * diameter:
-       */
-      return x*x+y*y < .25;
-   }
-
-   return 0; /* outside */
-}
-
-static int
-inside_circle_filled(const struct arg *arg, double x, double y)
-{
-   return circle_check(x, y, arg->x1, arg->y1, arg->x2, arg->y2);
-}
-
-static int
-circle_check_line(const struct arg *arg, double x, double y, double w)
-   /* Check for a point being inside the boundaries implied by the given arg
-    * and assuming a width 2*w each side of the boundaries.  This function has
-    * the same semantic as square_check_line but tests the circle.
-    */
-{
-   double cx = (arg->x1+arg->x2)/2;
-   double wx = fabs(arg->x1-arg->x2)/2;
-   double cy = (arg->y1+arg->y2)/2;
-   double wy = fabs(arg->y1-arg->y2)/2;
-
-   if (circle_check(x, y, cx-wx-w, cy-wy-w, cx+wx+w, cy+wy+w))
-   {
-      /* Inside, but maybe too far; check for the redundant case where
-       * the lines overlap:
-       */
-      wx -= w;
-      wy -= w;
-      if (wx > 0 && wy > 0 && circle_check(x, y, cx-wx, cy-wy, cx+wx, cy+wy))
-         return INSIDE; /* between (inside) the boundary lines. */
-
-      return 0; /* inside the lines themselves. */
-   }
-
-   return OUTSIDE; /* outside the boundary lines. */
-}
-
-static int
-check_circle_filled(const struct arg *arg, double x, double y)
-{
-   return circle_check_line(arg, x, y, FILTER_WIDTH);
-}
-
-static int
-inside_circle(const struct arg *arg, double x, double y)
-{
-   return circle_check_line(arg, x, y, arg->width/2) == 0;
-}
-
-static int
-check_circle(const struct arg *arg, double x, double y)
-{
-   /* Exactly as the 'square' code.  */
-   double w = arg->width/2;
-
-   if (circle_check_line(arg, x, y, w+FILTER_WIDTH) == 0)
-   {
-      w -= FILTER_WIDTH;
-
-      if (w > 0 && circle_check_line(arg, x, y, w) == 0)
-         return INSIDE;
-
-      /* Point is somewhere in the filter region: */
-      return 0;
-   }
-
-   else /* Inside or outside the square by more than w+FILTER_WIDTH. */
-      return OUTSIDE;
-}
-
-/* "line",
- * { NULL, NULL },  There is no 'filled' line.
- * { inside_line, check_line }
- */
-static int
-line_check(double x, double y, double x1, double y1, double x2, double y2,
-   double w, double expand)
-{
-   /* Shift all the points to (arg->x1, arg->y1) */
-   double lx = x2 - x1;
-   double ly = y2 - y1;
-   double len2 = lx*lx + ly*ly;
-   double cross, dot;
-
-   x -= x1;
-   y -= y1;
-
-   /* The dot product is the distance down the line, the cross product is
-    * the distance away from the line:
-    *
-    *    distance = |cross| / sqrt(len2) 
-    */
-   cross = x * ly - y * lx;
-
-   /* If 'distance' is more than w the point is definitely outside the line:
-    *
-    *     distance >= w
-    *     |cross|  >= w * sqrt(len2)
-    *     cross^2  >= w^2 * len2:
-    */
-   if (cross*cross >= (w+expand)*(w+expand)*len2)
-      return 0; /* outside */
-
-   /* Now find the distance *along* the line; this comes from the dot product
-    * lx.x+ly.y. The actual distance (in pixels) is:
-    *
-    *   distance = dot / sqrt(len2)
-    */
-   dot = lx * x + ly * y;
-
-   /* The test for 'outside' is:
-    *
-    *    distance < 0 || distance > sqrt(len2)
-    *                 -> dot / sqrt(len2) > sqrt(len2)
-    *                 -> dot > len2
-    *
-    * But 'expand' is used for the filter width and needs to be handled too:
-    */
-   return dot > -expand && dot < len2+expand;
-}
-
-static int
-inside_line(const struct arg *arg, double x, double y)
-{
-   return line_check(x, y, arg->x1, arg->y1, arg->x2, arg->y2, arg->width/2, 0);
-}
-
-static int
-check_line(const struct arg *arg, double x, double y)
-{
-   /* The end caps of the line must be checked too; it's not enough just to
-    * widen the line by FILTER_WIDTH; 'expand' exists for this purpose:
-    */
-   if (line_check(x, y, arg->x1, arg->y1, arg->x2, arg->y2, arg->width/2,
-       FILTER_WIDTH))
-   {
-      /* Inside the line+filter; far enough inside that the filter isn't
-       * required?
-       */
-      if (arg->width > 2*FILTER_WIDTH &&
-          line_check(x, y, arg->x1, arg->y1, arg->x2, arg->y2, arg->width/2,
-             -FILTER_WIDTH))
-         return INSIDE;
-
-      return 0;
-   }
-
-   return OUTSIDE;
-}
-
-static const struct
-{
-   const char    *name;
-   shape_fn_ptr   function[2/*fill,line*/][2];
-#  define         FN_INSIDE 0
-#  define         FN_CHECK 1
-} shape_defs[] =
-{
-   {  "square",
-      {  { inside_square_filled, check_square_filled },
-         { inside_square, check_square } }
-   },
-   {  "circle",
-      {  { inside_circle_filled, check_circle_filled },
-         { inside_circle, check_circle } }
-   },
-   {  "line",
-      {  { NULL, NULL },
-         { inside_line, check_line } }
-   }
-};
-
-#define shape_count ((sizeof shape_defs)/(sizeof shape_defs[0]))
-
-static shape_fn_ptr
-shape_of(const char *arg, double width, int f)
-{
-   unsigned int i;
-
-   for (i=0; i<shape_count; ++i) if (strcmp(shape_defs[i].name, arg) == 0)
-   {
-      shape_fn_ptr fn = shape_defs[i].function[width != 0][f];
-
-      if (fn != NULL)
-         return fn;
-
-      fprintf(stderr, "genpng: %s %s not supported\n",
-         width == 0 ? "filled" : "unfilled", arg);
-      exit(1);
-   }
-
-   fprintf(stderr, "genpng: %s: not a valid shape name\n", arg);
-   exit(1);
-}
-
-static void
-parse_arg(struct arg *arg, const char **argv/*7 arguments*/)
-{
-   /* shape ::= color width shape x1 y1 x2 y2 */
-   arg->color = color_of(argv[0]);
-   arg->width = width_of(argv[1]);
-   arg->inside_fn = shape_of(argv[2], arg->width, FN_INSIDE);
-   arg->check_fn = shape_of(argv[2], arg->width, FN_CHECK);
-   arg->x1 = coordinate_of(argv[3]);
-   arg->y1 = coordinate_of(argv[4]);
-   arg->x2 = coordinate_of(argv[5]);
-   arg->y2 = coordinate_of(argv[6]);
-}
-
-static png_uint_32
-read_wh(const char *name, const char *str)
-   /* read a PNG width or height */
-{
-   char *ep = NULL;
-   unsigned long ul = strtoul(str, &ep, 10);
-
-   if (ep != NULL && *ep == 0 && ul > 0 && ul <= 0x7fffffff)
-      return (png_uint_32)/*SAFE*/ul;
-
-   fprintf(stderr, "genpng: %s: invalid number %s\n", name, str);
-   exit(1);
-}
-
-static void
-pixel(png_uint_16p p, struct arg *args, int nargs, double x, double y)
-{
-   /* Fill in the pixel by checking each shape (args[nargs]) for effects on
-    * the corresponding sample:
-    */
-   double r=0, g=0, b=0, a=0;
-
-   while (--nargs >= 0 && a != 1)
-   {
-      /* NOTE: alpha_calc can return a value outside the range 0..1 with the
-       * bicubic filter.
-       */
-      const double alpha = alpha_calc(args+nargs, x, y) * (1-a);
-
-      r += alpha * args[nargs].color->red;
-      g += alpha * args[nargs].color->green;
-      b += alpha * args[nargs].color->blue;
-      a += alpha;
-   }
-
-   /* 'a' may be negative or greater than 1; if it is, negative clamp the
-    * pixel to 0 if >1 clamp r/g/b:
-    */
-   if (a > 0) 
-   {
-      if (a > 1)
-      {
-         if (r > 1) r = 1;
-         if (g > 1) g = 1;
-         if (b > 1) b = 1;
-         a = 1;
-      }
-
-      /* And fill in the pixel: */
-      p[0] = (png_uint_16)/*SAFE*/round(r * 65535);
-      p[1] = (png_uint_16)/*SAFE*/round(g * 65535);
-      p[2] = (png_uint_16)/*SAFE*/round(b * 65535);
-      p[3] = (png_uint_16)/*SAFE*/round(a * 65535);
-   }
-
-   else
-      p[3] = p[2] = p[1] = p[0] = 0;
-}
-
-int
-main(int argc, const char **argv)
-{
-   int convert_to_8bit = 0;
-
-   /* There is one option: --8bit: */
-   if (argc > 1 && strcmp(argv[1], "--8bit") == 0)
-      --argc, ++argv, convert_to_8bit = 1;
-
-   if (argc >= 3)
-   {
-      png_uint_16p buffer;
-      int nshapes;
-      png_image image;
-#     define max_shapes 256
-      struct arg arg_list[max_shapes];
-
-      /* The libpng Simplified API write code requires a fully initialized
-       * structure.
-       */
-      memset(&image, 0, sizeof image);
-      image.version = PNG_IMAGE_VERSION;
-      image.opaque = NULL;
-      image.width = read_wh("width", argv[1]);
-      image.height = read_wh("height", argv[2]);
-      image.format = PNG_FORMAT_LINEAR_RGB_ALPHA;
-      image.flags = 0;
-      image.colormap_entries = 0;
-
-      /* Check the remainder of the arguments */
-      for (nshapes=0; 3+7*(nshapes+1) <= argc && nshapes < max_shapes;
-           ++nshapes)
-         parse_arg(arg_list+nshapes, argv+3+7*nshapes);
-
-      if (3+7*nshapes != argc)
-      {
-         fprintf(stderr, "genpng: %s: too many arguments\n", argv[3+7*nshapes]);
-         return 1;
-      }
-
-      /* Create the buffer: */
-      buffer = malloc(PNG_IMAGE_SIZE(image));
-
-      if (buffer != NULL)
-      {
-         png_uint_32 y;
-
-         /* Write each row... */
-         for (y=0; y<image.height; ++y)
-         {
-            png_uint_32 x;
-
-            /* Each pixel in each row: */
-            for (x=0; x<image.width; ++x)
-               pixel(buffer + 4*(x + y*image.width), arg_list, nshapes, x, y);
-         }
-
-         /* Write the result (to stdout) */
-         if (png_image_write_to_stdio(&image, stdout, convert_to_8bit,
-             buffer, 0/*row_stride*/, NULL/*colormap*/))
-         {
-            free(buffer);
-            return 0; /* success */
-         }
-
-         else
-            fprintf(stderr, "genpng: write stdout: %s\n", image.message);
-
-         free(buffer);
-      }
-
-      else
-         fprintf(stderr, "genpng: out of memory: %lu bytes\n",
-               (unsigned long)PNG_IMAGE_SIZE(image));
-   }
-
-   else
-   {
-      /* Wrong number of arguments */
-      fprintf(stderr, "genpng: usage: genpng [--8bit] width height {shape}\n"
-         " Generate a transparent PNG in RGBA (truecolor+alpha) format\n"
-         " containing the given shape or shapes.  Shapes are defined:\n"
-         "\n"
-         "  shape ::= color width shape x1 y1 x2 y2\n"
-         "  color ::= black|white|red|green|yellow|blue\n"
-         "  color ::= brown|purple|pink|orange|gray|cyan\n"
-         "  width ::= filled|<number>\n"
-         "  shape ::= circle|square|line\n"
-         "  x1,x2 ::= <number>\n"
-         "  y1,y2 ::= <number>\n"
-         "\n"
-         " Numbers are floating point numbers describing points relative to\n"
-         " the top left of the output PNG as pixel coordinates.  The 'width'\n"
-         " parameter is either the width of the line (in output pixels) used\n"
-         " to draw the shape or 'filled' to indicate that the shape should\n"
-         " be filled with the color.\n"
-         "\n"
-         " Colors are interpreted loosely to give access to the eight full\n"
-         " intensity RGB values:\n"
-         "\n"
-         "  black, red, green, blue, yellow, cyan, purple, white,\n"
-         "\n"
-         " Cyan is full intensity blue+green; RGB(0,1,1), plus the following\n"
-         " lower intensity values:\n"
-         "\n"
-         "  brown:  red+orange:  RGB(0.5, 0.125, 0) (dark red+orange)\n"
-         "  pink:   red+white:   RGB(1.0, 0.5,   0.5)\n"
-         "  orange: red+yellow:  RGB(1.0, 0.5,   0)\n"
-         "  gray:   black+white: RGB(0.5, 0.5,   0.5)\n"
-         "\n"
-         " The RGB values are selected to make detection of aliasing errors\n"
-         " easy. The names are selected to make the description of errors\n"
-         " easy.\n"
-         "\n"
-         " The PNG is written to stdout, if --8bit is given a 32bpp RGBA sRGB\n"
-         " file is produced, otherwise a 64bpp RGBA linear encoded file is\n"
-         " written.\n");
-   }
-
-   return 1;
-}
--- 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 1.6.17 [March 26, 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) constcast(char*,s)
-#  define PNGZ_INPUT_CAST(b) constcast(png_bytep,b)
+#  define PNGZ_MSG_CAST(s) png_constcast(char*,s)
+#  define PNGZ_INPUT_CAST(b) png_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 voidcast(type, value) static_cast<type>(value)
-#  define constcast(type, value) const_cast<type>(value)
-#  define aligncast(type, value) \
+#  define png_voidcast(type, value) static_cast<type>(value)
+#  define png_constcast(type, value) const_cast<type>(value)
+#  define png_aligncast(type, value) \
   static_cast<type>(static_cast<void*>(value))
-#  define aligncastconst(type, value) \
+#  define png_aligncastconst(type, value) \
   static_cast<type>(static_cast<const void*>(value))
 #else
-#  define voidcast(type, value) (value)
-#  define constcast(type, value) ((type)(value))
-#  define aligncast(type, value) ((void*)(value))
-#  define aligncastconst(type, value) ((const void*)(value))
+#  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))
 #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 = voidcast(png_bytep, pv);
+   png_bytep bytes = png_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 = voidcast(IDAT_list*, malloc(IDAT_list_size(NULL, length)));
+      next = png_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 = voidcast(struct control*,
+   struct control *control = png_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 = voidcast(struct control*, file->alloc_ptr);
+   struct control *control = png_voidcast(struct control*, file->alloc_ptr);

   if (allocate_idat)
   {
--- 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 1.6.18beta06 - June 1, 2015
+ libpng version 1.6.17 - March 26, 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 1.6.18beta06 - June 1, 2015
+ libpng versions 0.97, January 1998, through 1.6.17 - March 26, 2015
 Updated and distributed by Glenn Randers-Pehrson
 Copyright (c) 1998-2015 Glenn Randers-Pehrson

@@ -4065,11 +4065,10 @@ a 16-bit linear encoded PNG file is written.

 With all APIs row_stride is handled as in the read APIs - it is the spacing
 from one row to the next in component sized units (float) and if negative
-indicates a bottom-up row layout in the buffer.  If you pass zero, libpng will
-calculate the row_stride for you from the width and number of channels.
+indicates a bottom-up row layout in the buffer.

 Note that the write API does not support interlacing, sub-8-bit pixels,
-indexed (paletted) images, or most ancillary chunks.
+and indexed (paletted) images.

 VI. Modifying/Customizing libpng

@@ -5110,23 +5109,6 @@ length, which resulted in PNG files that cannot be read beyond the bad iTXt
 chunk.  This error was fixed in libpng-1.6.3, and a tool (called
 contrib/tools/png-fix-itxt) has been added to the libpng distribution.

-Starting with libpng-1.6.17, the PNG_SAFE_LIMITS macro was eliminated
-and safe limits are used by default (users who need larger limits
-can still override them at compile time or run time, as described above).
-
-The new limits are
-                                default   spec limit
-   png_user_width_max         1,000,000  2,147,483,647
-   png_user_height_max        1,000,000  2,147,483,647
-   png_user_chunk_cache_max         128  unlimited
-   png_user_chunk_malloc_max  8,000,000  unlimited
-
-Starting with libpng-1.6.18, a PNG_RELEASE_BUILD macro was added, which allows
-library builders to control compilation for an installed system (a release build).
-It can be set for testing debug or beta builds to ensure that they will compile
-when the build type is switched to RC or STABLE. In essence this overrides the
-PNG_LIBPNG_BUILD_BASE_TYPE definition which is not directly user controllable.
-
 XIII.  Detecting libpng

 The png_get_io_ptr() function has been present since libpng-0.88, has never
@@ -5297,13 +5279,13 @@ Other rules can be inferred by inspecting the libpng source.

 XVI. Y2K Compliance in libpng

-June 1, 2015
+March 26, 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 1.6.18beta06 are Y2K compliant.  It is my belief that earlier
+upward through 1.6.17 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 "June 1, 2015"
+.TH LIBPNG 3 "March 26, 2015"
 .SH NAME
-libpng \- Portable Network Graphics (PNG) Reference Library 1.6.18beta06
+libpng \- Portable Network Graphics (PNG) Reference Library 1.6.17
 .SH SYNOPSIS
 \fB
 #include <png.h>\fP
@@ -504,7 +504,7 @@ 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 1.6.18beta06 - June 1, 2015
+ libpng version 1.6.17 - March 26, 2015
 Updated and distributed by Glenn Randers-Pehrson
 <glennrp at users.sourceforge.net>
 Copyright (c) 1998-2015 Glenn Randers-Pehrson
@@ -515,7 +515,7 @@ libpng-manual.txt - A description on how to use and modify libpng

 Based on:

- libpng versions 0.97, January 1998, through 1.6.18beta06 - June 1, 2015
+ libpng versions 0.97, January 1998, through 1.6.17 - March 26, 2015
 Updated and distributed by Glenn Randers-Pehrson
 Copyright (c) 1998-2015 Glenn Randers-Pehrson

@@ -4569,11 +4569,10 @@ a 16-bit linear encoded PNG file is written.

 With all APIs row_stride is handled as in the read APIs - it is the spacing
 from one row to the next in component sized units (float) and if negative
-indicates a bottom-up row layout in the buffer.  If you pass zero, libpng will
-calculate the row_stride for you from the width and number of channels.
+indicates a bottom-up row layout in the buffer.

 Note that the write API does not support interlacing, sub-8-bit pixels,
-indexed (paletted) images, or most ancillary chunks.
+and indexed (paletted) images.

 .SH VI. Modifying/Customizing libpng

@@ -5614,23 +5613,6 @@ length, which resulted in PNG files that cannot be read beyond the bad iTXt
 chunk.  This error was fixed in libpng-1.6.3, and a tool (called
 contrib/tools/png-fix-itxt) has been added to the libpng distribution.

-Starting with libpng-1.6.17, the PNG_SAFE_LIMITS macro was eliminated
-and safe limits are used by default (users who need larger limits
-can still override them at compile time or run time, as described above).
-
-The new limits are
-                                default   spec limit
-   png_user_width_max         1,000,000  2,147,483,647
-   png_user_height_max        1,000,000  2,147,483,647
-   png_user_chunk_cache_max         128  unlimited
-   png_user_chunk_malloc_max  8,000,000  unlimited
-
-Starting with libpng-1.6.18, a PNG_RELEASE_BUILD macro was added, which allows
-library builders to control compilation for an installed system (a release build).
-It can be set for testing debug or beta builds to ensure that they will compile
-when the build type is switched to RC or STABLE. In essence this overrides the
-PNG_LIBPNG_BUILD_BASE_TYPE definition which is not directly user controllable.
-
 .SH XIII.  Detecting libpng

 The png_get_io_ptr() function has been present since libpng-0.88, has never
@@ -5801,13 +5783,13 @@ Other rules can be inferred by inspecting the libpng source.

 .SH XVI. Y2K Compliance in libpng

-June 1, 2015
+March 26, 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 1.6.18beta06 are Y2K compliant.  It is my belief that earlier
+upward through 1.6.17 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 +6044,6 @@ 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]
- 1.6.18beta01-06     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 +6100,7 @@ possible without all of you.

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

-Libpng version 1.6.18beta06 - June 1, 2015:
+Libpng version 1.6.17 - March 26, 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).

@@ -6142,7 +6123,7 @@ this sentence.

 This code is released under the libpng license.

-libpng versions 1.2.6, August 15, 2004, through 1.6.18beta06, June 1, 2015, are
+libpng versions 1.2.6, August 15, 2004, through 1.6.17, March 26, 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
@@ -6241,7 +6222,7 @@ certification mark of the Open Source Initiative.

 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-June 1, 2015
+March 26, 2015

 .\" end of man page

--- a/libpngpf.3
+++ b/libpngpf.3
@@ -1,6 +1,6 @@
-.TH LIBPNGPF 3 "June 1, 2015"
+.TH LIBPNGPF 3 "March 26, 2015"
 .SH NAME
-libpng \- Portable Network Graphics (PNG) Reference Library 1.6.18beta06
+libpng \- Portable Network Graphics (PNG) Reference Library 1.6.17
 (private functions)
 .SH SYNOPSIS
 \fB#include \fI"pngpriv.h"
--- a/png.5
+++ b/png.5
@@ -1,4 +1,4 @@
-.TH PNG 5 "June 1, 2015"
+.TH PNG 5 "March 26, 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 1.6.17 [March 26, 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_18beta06 Your_png_h_is_not_version_1_6_18beta06;
+typedef png_libpng_version_1_6_17 Your_png_h_is_not_version_1_6_17;

 /* 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
@@ -101,7 +101,7 @@ png_zfree(voidpf png_ptr, voidpf ptr)
 void /* PRIVATE */
 png_reset_crc(png_structrp png_ptr)
 {
-   /* The cast is safe because the crc is a 32-bit value. */
+   /* The cast is safe because the crc is a 32 bit value. */
   png_ptr->crc = (png_uint_32)crc32(0, Z_NULL, 0);
 }

@@ -129,7 +129,7 @@ png_calculate_crc(png_structrp png_ptr, png_const_bytep ptr, png_size_t length)
   }

   /* 'uLong' is defined in zlib.h as unsigned long; this means that on some
-    * systems it is a 64-bit value.  crc32, however, returns 32 bits so the
+    * systems it is a 64 bit value.  crc32, however, returns 32 bits so the
    * following cast is safe.  'uInt' may be no more than 16 bits, so it is
    * necessary to perform a loop here.
    */
@@ -275,9 +275,7 @@ png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr,

 #  ifdef PNG_SETJMP_SUPPORTED
      if (!setjmp(create_jmp_buf))
-#  endif
      {
-#  ifdef PNG_SETJMP_SUPPORTED
         /* Temporarily fake out the longjmp information until we have
          * successfully completed this function.  This only works if we have
          * setjmp() support compiled in, but it is safe - this stuff should
@@ -286,6 +284,8 @@ png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
         create_struct.jmp_buf_ptr = &create_jmp_buf;
         create_struct.jmp_buf_size = 0; /*stack allocation*/
         create_struct.longjmp_fn = longjmp;
+#  else
+      {
 #  endif
         /* Call the general version checker (shared with read and write code):
          */
@@ -766,13 +766,13 @@ png_get_copyright(png_const_structrp png_ptr)
 #else
 #  ifdef __STDC__
   return PNG_STRING_NEWLINE \
-     "libpng version 1.6.18beta06 - June 1, 2015" PNG_STRING_NEWLINE \
+     "libpng version 1.6.17 - March 26, 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 1.6.18beta06 - June 1, 2015\
+      return "libpng version 1.6.17 - March 26, 2015\
      Copyright (c) 1998-2015 Glenn Randers-Pehrson\
      Copyright (c) 1996-1997 Andreas Dilger\
      Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
@@ -1235,17 +1235,16 @@ png_XYZ_from_xy(png_XYZ *XYZ, const png_xy *xy)

   /* Check xy and, implicitly, z.  Note that wide gamut color spaces typically
    * have end points with 0 tristimulus values (these are impossible end
-    * points, but they are used to cover the possible colors).  We check
-    * xy->whitey against 5, not 0, to avoid a possible integer overflow.
+    * points, but they are used to cover the possible colors.)
    */
-   if (xy->redx   < 0 || xy->redx > PNG_FP_1) return 1;
-   if (xy->redy   < 0 || xy->redy > PNG_FP_1-xy->redx) return 1;
+   if (xy->redx < 0 || xy->redx > PNG_FP_1) return 1;
+   if (xy->redy < 0 || xy->redy > PNG_FP_1-xy->redx) return 1;
   if (xy->greenx < 0 || xy->greenx > PNG_FP_1) return 1;
   if (xy->greeny < 0 || xy->greeny > PNG_FP_1-xy->greenx) return 1;
-   if (xy->bluex  < 0 || xy->bluex > PNG_FP_1) return 1;
-   if (xy->bluey  < 0 || xy->bluey > PNG_FP_1-xy->bluex) return 1;
+   if (xy->bluex < 0 || xy->bluex > PNG_FP_1) return 1;
+   if (xy->bluey < 0 || xy->bluey > PNG_FP_1-xy->bluex) return 1;
   if (xy->whitex < 0 || xy->whitex > PNG_FP_1) return 1;
-   if (xy->whitey < 5 || xy->whitey > PNG_FP_1-xy->whitex) return 1;
+   if (xy->whitey < 0 || xy->whitey > PNG_FP_1-xy->whitex) return 1;

   /* The reverse calculation is more difficult because the original tristimulus
    * value had 9 independent values (red,green,blue)x(X,Y,Z) however only 8
@@ -2277,7 +2276,7 @@ png_compare_ICC_profile_with_sRGB(png_const_structrp png_ptr,

         /* Length *and* intent must match */
         if (length == png_sRGB_checks[i].length &&
-            intent == (png_uint_32) png_sRGB_checks[i].intent)
+            intent == png_sRGB_checks[i].intent)
         {
            /* Now calculate the adler32 if not done already. */
            if (adler == 0)
@@ -4237,7 +4236,7 @@ png_set_option(png_structrp png_ptr, int option, int onoff)
 * contrib/tools/makesRGB.c.  The actual sRGB transfer curve defined in the
 * specification (see the article at http://en.wikipedia.org/wiki/SRGB)
 * is used, not the gamma=1/2.2 approximation use elsewhere in libpng.
- * The sRGB to linear table is exact (to the nearest 16-bit linear fraction).
+ * The sRGB to linear table is exact (to the nearest 16 bit linear fraction).
 * The inverse (linear to sRGB) table has accuracies as follows:
 *
 * For all possible (255*65535+1) input values:
--- a/png.h
+++ b/png.h
@@ -1,7 +1,7 @@

 /* png.h - header file for PNG reference library
 *
- * libpng version 1.6.18beta06, June 1, 2015
+ * libpng version 1.6.17, March 26, 2015
 *
 * Copyright (c) 1998-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
@@ -12,7 +12,7 @@
 * Authors and maintainers:
 *   libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
 *   libpng versions 0.89c, June 1996, through 0.96, May 1997: Andreas Dilger
- *   libpng versions 0.97, January 1998, through 1.6.18beta06, June 1, 2015: Glenn
+ *   libpng versions 0.97, January 1998, through 1.6.17, March 26, 2015: Glenn
 *   See also "Contributing Authors", below.
 *
 * Note about libpng version numbers:
@@ -216,7 +216,6 @@
 *    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]
- *    1.6.18beta01-06         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
@@ -248,7 +247,7 @@
 *
 * This code is released under the libpng license.
 *
- * libpng versions 1.2.6, August 15, 2004, through 1.6.18beta06, June 1, 2015, are
+ * libpng versions 1.2.6, August 15, 2004, through 1.6.17, March 26, 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:
@@ -360,13 +359,13 @@
 * Y2K compliance in libpng:
 * =========================
 *
- *    June 1, 2015
+ *    March 26, 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 1.6.18beta06 are Y2K compliant.  It is my belief that
+ *    upward through 1.6.17 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 "1.6.18beta06"
+#define PNG_LIBPNG_VER_STRING "1.6.17"
 #define PNG_HEADER_VERSION_STRING \
-     " libpng version 1.6.18beta06 - June 1, 2015\n"
+     " libpng version 1.6.17 - March 26, 2015\n"

 #define PNG_LIBPNG_VER_SONUM   16
 #define PNG_LIBPNG_VER_DLLNUM  16
@@ -438,13 +437,13 @@
 /* These should match the first 3 components of PNG_LIBPNG_VER_STRING: */
 #define PNG_LIBPNG_VER_MAJOR   1
 #define PNG_LIBPNG_VER_MINOR   6
-#define PNG_LIBPNG_VER_RELEASE 18
+#define PNG_LIBPNG_VER_RELEASE 17

 /* This should match the numeric part of the final component of
 * PNG_LIBPNG_VER_STRING, omitting any leading zero:
 */

-#define PNG_LIBPNG_VER_BUILD  06
+#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.
@@ -469,7 +468,7 @@
 * version 1.0.0 was mis-numbered 100 instead of 10000).  From
 * version 1.0.1 it's    xxyyzz, where x=major, y=minor, z=release
 */
-#define PNG_LIBPNG_VER 10618 /* 1.6.18 */
+#define PNG_LIBPNG_VER 10617 /* 1.6.17 */

 /* Library configuration: these options cannot be changed after
 * the library has been built.
@@ -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_18beta06;
+typedef char* png_libpng_version_1_6_17;

 /* Basic control structions.  Read libpng-manual.txt or libpng.3 for more info.
 *
@@ -1624,7 +1623,35 @@ 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 /* DEPRECATED */
+#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.
+ */
 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))
@@ -2756,9 +2783,8 @@ PNG_EXPORT(207, void, png_save_uint_16, (png_bytep buf, unsigned int i));
 *
 * To read a PNG file using the simplified API:
 *
- * 1) Declare a 'png_image' structure (see below) on the stack, set the
- *    version field to PNG_IMAGE_VERSION and the 'opaque' pointer to NULL
- *    (this is REQUIRED, your program may crash if you don't do it.)
+ * 1) Declare a 'png_image' structure (see below) on the stack and set the
+ *    version field to PNG_IMAGE_VERSION.
 * 2) Call the appropriate png_image_begin_read... function.
 * 3) Set the png_image 'format' member to the required sample format.
 * 4) Allocate a buffer for the image and, if required, the color-map.
@@ -3183,11 +3209,9 @@ PNG_EXPORT(240, int, png_image_write_to_stdio, (png_imagep image, FILE *file,
 *
 * With all APIs row_stride is handled as in the read APIs - it is the spacing
 * from one row to the next in component sized units (1 or 2 bytes) and if
- * negative indicates a bottom-up row layout in the buffer.  If row_stride is zero,
- * libpng will calculate it for you from the image width and number of channels.
+ * negative indicates a bottom-up row layout in the buffer.
 *
- * Note that the write API does not support interlacing, sub-8-bit pixels, indexed
- * PNG (color_type 3) or most ancillary chunks.
+ * Note that the write API does not support interlacing or sub-8-bit pixels.
 */
 #endif /* STDIO */
 #endif /* SIMPLIFIED_WRITE */
--- a/pngconf.h
+++ b/pngconf.h
@@ -1,7 +1,7 @@

 /* pngconf.h - machine configurable file for libpng
 *
- * libpng version 1.6.18beta06, (PENDING RELEASE)
+ * libpng version 1.6.17, March 26, 2015
 *
 * Copyright (c) 1998-2015 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
--- a/pngmem.c
+++ b/pngmem.c
@@ -77,9 +77,6 @@ png_malloc_base,(png_const_structrp png_ptr, png_alloc_size_t size),
   PNG_UNUSED(png_ptr)
 #endif

-   /* Some compilers complain that this is always true.  However, it
-    * can be false when integer overflow happens.
-    */
   if (size > 0 && size <= PNG_SIZE_MAX
 #     ifdef PNG_MAX_MALLOC_64K
         && size <= 65536U
--- 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 1.6.17 [March 26, 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.)
@@ -584,11 +584,13 @@ png_push_save_buffer(png_structrp png_ptr)
      if (png_ptr->save_buffer == NULL)
      {
         png_free(png_ptr, old_buffer);
+         old_buffer = NULL;
         png_error(png_ptr, "Insufficient memory for save_buffer");
      }

      memcpy(png_ptr->save_buffer, old_buffer, png_ptr->save_buffer_size);
      png_free(png_ptr, old_buffer);
+      old_buffer = NULL;
      png_ptr->save_buffer_max = new_max;
   }
   if (png_ptr->current_buffer_size)
--- 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 1.6.17 [March 26, 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.)
@@ -118,12 +118,8 @@
    * to compile with an appropriate #error if ALIGNED_MEMORY has been turned
    * off.
    *
-    * Note that gcc-4.9 defines __ARM_NEON instead of the deprecated
-    * __ARM_NEON__, so we check both variants.
-    *
-    * To disable ARM_NEON optimizations entirely, and skip compiling the
-    * associated assembler code, pass --enable-arm-neon=no to configure
-    * or put -DPNG_ARM_NEON_OPT=0 in CPPFLAGS.
+    * Note that gcc-4.9 defines __ARM_NEON instead of __ARM_NEON__, so we
+    * check both variants.
    */
 #  if (defined(__ARM_NEON__) || defined(__ARM_NEON)) && \
   defined(PNG_ALIGNED_MEMORY_SUPPORTED)
@@ -300,22 +296,6 @@
 #  define PNG_DLL_EXPORT
 #endif

-/* This is a global switch to set the compilation for an installed system
- * (a release build).  It can be set for testing debug builds to ensure that
- * they will compile when the build type is switched to RC or STABLE, the
- * default is just to use PNG_LIBPNG_BUILD_BASE_TYPE.  Set this in CPPFLAGS
- * with either:
- *
- *   -DPNG_RELEASE_BUILD Turns on the release compile path
- *   -DPNG_RELEASE_BUILD=0 Turns it off
- * or in your pngusr.h with
- *   #define PNG_RELEASE_BUILD=1 Turns on the release compile path
- *   #define PNG_RELEASE_BUILD=0 Turns it off
- */
-#ifndef PNG_RELEASE_BUILD
-#  define PNG_RELEASE_BUILD (PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC)
-#endif
-
 /* SECURITY and SAFETY:
 *
 * libpng is built with support for internal limits on image dimensions and
--- a/pngread.c
+++ b/pngread.c
@@ -63,7 +63,7 @@ png_create_read_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
         /* In stable builds only warn if an application error can be completely
          * handled.
          */
-#        if PNG_RELEASE_BUILD
+#        if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
            png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;
 #        endif
 #     endif
--- 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 1.6.17 [March 26, 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 == gray)
                     *dp-- = 0;

                  else
@@ -4478,8 +4478,7 @@ 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) == gray_high && *(sp) == 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 1.6.17 [March 26, 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.)
@@ -341,7 +341,7 @@ png_inflate_claim(png_structrp png_ptr, png_uint_32 owner)
       * are minimal.
       */
      (void)png_safecat(msg, (sizeof msg), 4, " using zstream");
-#if PNG_RELEASE_BUILD
+#if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
      png_chunk_warning(png_ptr, msg);
      png_ptr->zowner = 0;
 #else
@@ -575,7 +575,7 @@ png_decompress_chunk(png_structrp png_ptr,
    */
   png_alloc_size_t limit = PNG_SIZE_MAX;

-# ifdef PNG_SET_USER_LIMITS_SUPPORTED
+# ifdef PNG_SET_CHUNK_MALLOC_LIMIT_SUPPORTED
   if (png_ptr->user_chunk_malloc_max > 0 &&
       png_ptr->user_chunk_malloc_max < limit)
      limit = png_ptr->user_chunk_malloc_max;
@@ -670,6 +670,7 @@ png_decompress_chunk(png_structrp png_ptr,
                   * success)
                   */
                  png_free(png_ptr, text);
+                  text = NULL;

                  /* This really is very benign, but it's still an error because
                   * the extra space may otherwise be used as a Trojan Horse.
@@ -1816,8 +1817,7 @@ png_handle_tRNS(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
         return;
      }

-      if (length > png_ptr->num_palette ||
-         length > (unsigned int) PNG_MAX_PALETTE_LENGTH ||
+      if (length > png_ptr->num_palette || length > PNG_MAX_PALETTE_LENGTH ||
         length == 0)
      {
         png_crc_finish(png_ptr, length);
@@ -1980,7 +1980,7 @@ png_handle_hIST(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)

   num = length / 2 ;

-   if (num != png_ptr->num_palette || num > (unsigned int) PNG_MAX_PALETTE_LENGTH)
+   if (num != png_ptr->num_palette || num > PNG_MAX_PALETTE_LENGTH)
   {
      png_crc_finish(png_ptr, length);
      png_chunk_benign_error(png_ptr, "invalid");
@@ -2715,7 +2715,7 @@ png_cache_unknown_chunk(png_structrp png_ptr, png_uint_32 length)
      png_ptr->unknown_chunk.data = NULL;
   }

-#  ifdef PNG_SET_USER_LIMITS_SUPPORTED
+#  ifdef PNG_SET_CHUNK_MALLOC_LIMIT_SUPPORTED
      if (png_ptr->user_chunk_malloc_max > 0 &&
          png_ptr->user_chunk_malloc_max < limit)
         limit = png_ptr->user_chunk_malloc_max;
--- 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 1.6.17 [March 26, 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.)
@@ -673,6 +673,7 @@ png_set_iCCP(png_const_structrp png_ptr, png_inforp info_ptr,
   if (new_iccp_profile == NULL)
   {
      png_free(png_ptr, new_iccp_name);
+      new_iccp_name = NULL;
      png_benign_error(png_ptr,
          "Insufficient memory to process iCCP profile");

@@ -709,7 +710,7 @@ png_set_text_2(png_const_structrp png_ptr, png_inforp info_ptr,
 {
   int i;

-   png_debug1(1, "in %lx storage function", png_ptr == NULL ? 0xabadca11 :
+   png_debug1(1, "in %lx storage function", png_ptr == NULL ? "unexpected" :
      (unsigned long)png_ptr->chunk_name);

   if (png_ptr == NULL || info_ptr == NULL || num_text <= 0 || text_ptr == NULL)
@@ -1521,9 +1522,6 @@ png_set_compression_buffer_size(png_structrp png_ptr, png_size_t size)
         }

 #ifndef __COVERITY__
-         /* Some compilers complain that this is always false.  However, it
-          * can be true when integer overflow happens.
-          */
         if (size > ZLIB_IO_MAX)
         {
            png_warning(png_ptr,
--- a/pngstruct.h
+++ b/pngstruct.h
@@ -1,8 +1,8 @@

 /* pngstruct.h - header file for PNG reference library
 *
- * Last changed in libpng 1.6.18 [(PENDING RELEASE)]
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.1 [March 28, 2013]
+ * Copyright (c) 1998-2013 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.)
 *
@@ -219,18 +219,16 @@ 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.
-                               * While reading this is a pointer into
-                               * big_prev_row; while writing it is separately
-                               * allocated if needed.
+                               * This is a pointer into big_prev_row
                               */
   png_bytep row_buf;         /* buffer to save current (unfiltered) row.
-                               * While reading, this is a pointer into
-                               * big_row_buf; while writing it is separately
-                               * allocated.
+                               * This is a pointer into big_row_buf
                               */
-#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 */
+#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 */
 #endif
   png_size_t info_rowbytes;  /* Added in 1.5.4: cache of updated row bytes */

--- 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 1.6.17 [March 26, 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.)
@@ -565,7 +565,6 @@ png_debug_free(png_structp png_ptr, png_voidp ptr)
   }

   /* Unlink the element from the list. */
-   if (pinformation != NULL)
   {
      memory_infop *ppinfo = &pinformation;

@@ -582,7 +581,8 @@ png_debug_free(png_structp png_ptr, png_voidp ptr)
            /* We must free the list element too, but first kill
               the memory that is to be freed. */
            memset(ptr, 0x55, pinfo->size);
-            free(pinfo);
+            if (pinfo != NULL)
+               free(pinfo);
            pinfo = NULL;
            break;
         }
@@ -1833,10 +1833,10 @@ main(int argc, char *argv[])
                     k, (unsigned long)filters_used[k]);
 #endif
 #ifdef PNG_TIME_RFC1123_SUPPORTED
-            if (tIME_chunk_present != 0)
-               fprintf(STDERR, " tIME = %s\n", tIME_string);
+         if (tIME_chunk_present != 0)
+            fprintf(STDERR, " tIME = %s\n", tIME_string);

-            tIME_chunk_present = 0;
+         tIME_chunk_present = 0;
 #endif /* TIME_RFC1123 */
         }

@@ -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_18beta06 Your_png_h_is_not_version_1_6_18beta06;
+typedef png_libpng_version_1_6_17 Your_png_h_is_not_version_1_6_17;
--- 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 1.6.17 [March 26, 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.)
@@ -704,7 +704,7 @@ png_do_check_palette_indexes(png_structrp png_ptr, png_row_infop row_info)
             */
            for (; rp > png_ptr->row_buf; rp--)
            {
-              if ((*rp >> padding) != 0)
+              if (*rp >> padding != 0)
                 png_ptr->num_palette_max = 1;
              padding = 0;
            }
--- a/pngwrite.c
+++ b/pngwrite.c
@@ -1,7 +1,7 @@

 /* pngwrite.c - general routines to write a PNG file
 *
- * Last changed in libpng 1.6.18 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.17 [March 26, 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.)
@@ -216,13 +216,8 @@ png_write_info(png_structrp png_ptr, png_const_inforp info_ptr)
      if ((png_ptr->transformations & PNG_INVERT_ALPHA) != 0 &&
          info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
      {
-         int j, jend;
-
-         jend = info_ptr->num_trans;
-         if (jend > PNG_MAX_PALETTE_LENGTH)
-            jend = PNG_MAX_PALETTE_LENGTH;
-
-         for (j = 0; j<jend; ++j)
+         int j;
+         for (j = 0; j<(int)info_ptr->num_trans; j++)
            info_ptr->trans_alpha[j] =
               (png_byte)(255 - info_ptr->trans_alpha[j]);
      }
@@ -543,7 +538,7 @@ png_create_write_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
      /* App warnings are warnings in release (or release candidate) builds but
       * are errors during development.
       */
-#if PNG_RELEASE_BUILD
+#if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
      png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;
 #endif

@@ -922,6 +917,10 @@ 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)
@@ -938,11 +937,24 @@ 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->try_row);
-   png_free(png_ptr, png_ptr->tst_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_ptr->prev_row = NULL;
-   png_ptr->try_row = NULL;
-   png_ptr->tst_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;
 #endif

 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
@@ -1040,67 +1052,75 @@ 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)
      {
-         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)
+#ifdef PNG_WRITE_FILTER_SUPPORTED
+         if ((png_ptr->do_filter & PNG_FILTER_SUB) != 0 &&
+             png_ptr->sub_row == NULL)
         {
-            /* 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);
+            png_ptr->sub_row = (png_bytep)png_malloc(png_ptr,
+                (png_ptr->rowbytes + 1));
+            png_ptr->sub_row[0] = PNG_FILTER_VALUE_SUB;
         }

-         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_malloc(png_ptr, buf_size);
-
-         if (num_filters > 1)
+         if ((png_ptr->do_filter & PNG_FILTER_UP) != 0 &&
+              png_ptr->up_row == NULL)
         {
-            if (png_ptr->tst_row == NULL)
-               png_ptr->tst_row = png_malloc(png_ptr, buf_size);
+            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->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;
   }
   else
      png_error(png_ptr, "Unknown custom filter method");
@@ -1114,18 +1134,174 @@ png_set_filter(png_structrp png_ptr, int method, int filters)
 * better compression.
 */
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED      /* GRR 970116 */
-/* Provide floating and fixed point APIs (DEPRECATED) */
+/* 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;
+   }
+}
+
+/* Provide floating and fixed point APIs */
 #ifdef PNG_FLOATING_POINT_SUPPORTED
 void PNGAPI
 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_UNUSED(png_ptr)
-   PNG_UNUSED(heuristic_method)
-   PNG_UNUSED(num_weights)
-   PNG_UNUSED(filter_weights)
-   PNG_UNUSED(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);
+      }
+   }
 }
 #endif /* FLOATING_POINT */

@@ -1135,11 +1311,63 @@ 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_UNUSED(png_ptr)
-   PNG_UNUSED(heuristic_method)
-   PNG_UNUSED(num_weights)
-   PNG_UNUSED(filter_weights)
-   PNG_UNUSED(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;
+      }
+   }
 }
 #endif /* FIXED_POINT */
 #endif /* WRITE_WEIGHTED_FILTER */
--- 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 1.6.17 [March 26, 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.)
@@ -422,7 +422,7 @@ png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
               *(dp++) = *(sp++);
               */
               sp+=3; dp = sp;
-               *dp = (png_byte)(255 - *(sp++));
+               *(dp++) = (png_byte)(255 - *(sp++));
            }
         }

@@ -446,7 +446,7 @@ png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
               */
               sp+=6; dp = sp;
               *(dp++) = (png_byte)(255 - *(sp++));
-               *dp     = (png_byte)(255 - *(sp++));
+               *(dp++) = (png_byte)(255 - *(sp++));
            }
         }
 #endif /* WRITE_16BIT */
@@ -484,7 +484,7 @@ png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
               */
               sp+=2; dp = sp;
               *(dp++) = (png_byte)(255 - *(sp++));
-               *dp     = (png_byte)(255 - *(sp++));
+               *(dp++) = (png_byte)(255 - *(sp++));
            }
         }
 #endif /* WRITE_16BIT */
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -1,7 +1,7 @@

 /* pngwutil.c - utilities to write a PNG file
 *
- * Last changed in libpng 1.6.18 [(PENDING RELEASE)]
+ * Last changed in libpng 1.6.17 [March 26, 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.)
@@ -308,7 +308,7 @@ png_deflate_claim(png_structrp png_ptr, png_uint_32 owner,
       */
      (void)png_safecat(msg, (sizeof msg), 10, " using zstream");
 #endif
-#if PNG_RELEASE_BUILD
+#if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
         png_warning(png_ptr, msg);

         /* Attempt sane error recovery */
@@ -1961,10 +1961,6 @@ png_write_start_row(png_structrp png_ptr)
   png_alloc_size_t buf_size;
   int usr_pixel_depth;

-#ifdef PNG_WRITE_FILTER_SUPPORTED
-   int filters;
-#endif
-
   png_debug(1, "in png_write_start_row");

   usr_pixel_depth = png_ptr->usr_channels * png_ptr->usr_bit_depth;
@@ -1975,53 +1971,50 @@ png_write_start_row(png_structrp png_ptr)
   png_ptr->maximum_pixel_depth = (png_byte)usr_pixel_depth;

   /* Set up row buffer */
-   png_ptr->row_buf = png_voidcast(png_bytep, png_malloc(png_ptr, buf_size));
+   png_ptr->row_buf = (png_bytep)png_malloc(png_ptr, buf_size);

   png_ptr->row_buf[0] = PNG_FILTER_VALUE_NONE;

 #ifdef PNG_WRITE_FILTER_SUPPORTED
-   filters = png_ptr->do_filter;
-
-   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 == 0)
-      filters = PNG_FILTER_NONE;
-
-   png_ptr->do_filter = filters;
-
-   if (((filters & (PNG_FILTER_SUB | PNG_FILTER_UP | PNG_FILTER_AVG |
-       PNG_FILTER_PAETH)) != 0) && png_ptr->try_row == NULL)
+   /* Set up filtering buffer, if using this filter */
+   if (png_ptr->do_filter & PNG_FILTER_SUB)
   {
-      int num_filters = 0;
+      png_ptr->sub_row = (png_bytep)png_malloc(png_ptr, png_ptr->rowbytes + 1);

-      png_ptr->try_row = png_voidcast(png_bytep, png_malloc(png_ptr, buf_size));
-
-      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++;
-
-      if (num_filters > 1)
-         png_ptr->tst_row = png_voidcast(png_bytep, png_malloc(png_ptr,
-             buf_size));
+      png_ptr->sub_row[0] = PNG_FILTER_VALUE_SUB;
   }

-   /* We only need to keep the previous row if we are using one of the following
-    * filters.
-    */
-   if ((filters & (PNG_FILTER_AVG | PNG_FILTER_UP | PNG_FILTER_PAETH)) != 0)
-      png_ptr->prev_row = png_calloc(png_ptr, buf_size);
+   /* We only need to keep the previous row if we are using one of these. */
+   if ((png_ptr->do_filter &
+      (PNG_FILTER_AVG | PNG_FILTER_UP | PNG_FILTER_PAETH)) != 0)
+   {
+      /* Set up previous row buffer */
+      png_ptr->prev_row = (png_bytep)png_calloc(png_ptr, buf_size);
+
+      if ((png_ptr->do_filter & PNG_FILTER_UP) != 0)
+      {
+         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->do_filter & PNG_FILTER_AVG) != 0)
+      {
+         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 = (png_bytep)png_malloc(png_ptr,
+             png_ptr->rowbytes + 1);
+
+         png_ptr->paeth_row[0] = PNG_FILTER_VALUE_PAETH;
+      }
+   }
 #endif /* WRITE_FILTER */

 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
@@ -2317,7 +2310,6 @@ png_do_write_interlace(png_row_infop row_info, png_bytep row, int pass)
 }
 #endif

-
 /* This filters the row, chooses which filter to use, if it has not already
 * been specified by the application, and then writes the row out with the
 * chosen filter.
@@ -2326,172 +2318,42 @@ static void /* PRIVATE */
 png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
   png_size_t row_bytes);

-#ifdef PNG_WRITE_FILTER_SUPPORTED
-static png_size_t /* PRIVATE */
-png_setup_sub_row(png_structrp png_ptr, const png_uint_32 bpp,
-    const png_size_t row_bytes, const png_size_t lmins)
-{
-   png_bytep rp, dp, lp;
-   png_size_t i;
-   png_size_t sum = 0;
-   int v;
-
-   png_ptr->try_row[0] = PNG_FILTER_VALUE_SUB;
-
-   for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1; i < bpp;
-        i++, rp++, dp++)
-   {
-      v = *dp = *rp;
-      sum += (v < 128) ? v : 256 - v;
-   }
-
-   for (lp = png_ptr->row_buf + 1; i < row_bytes;
-      i++, rp++, lp++, dp++)
-   {
-      v = *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
-      sum += (v < 128) ? v : 256 - v;
-
-      if (sum > lmins)  /* We are already worse, don't continue. */
-        break;
-   }
-
-   return (sum);
-}
-
-static png_size_t /* PRIVATE */
-png_setup_up_row(png_structrp png_ptr, const png_size_t row_bytes,
-    const png_size_t lmins)
-{
-   png_bytep rp, dp, pp;
-   png_size_t i;
-   png_size_t sum = 0;
-   int v;
-
-   png_ptr->try_row[0] = PNG_FILTER_VALUE_UP;
-
-   for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
-       pp = png_ptr->prev_row + 1; i < row_bytes;
-       i++, rp++, pp++, dp++)
-   {
-      v = *dp = (png_byte)(((int)*rp - (int)*pp) & 0xff);
-      sum += (v < 128) ? v : 256 - v;
-
-      if (sum > lmins)  /* We are already worse, don't continue. */
-        break;
-   }
-
-   return (sum);
-}
-
-static png_size_t /* PRIVATE */
-png_setup_avg_row(png_structrp png_ptr, const png_uint_32 bpp,
-      const png_size_t row_bytes, const png_size_t lmins)
-{
-   png_bytep rp, dp, pp, lp;
-   png_uint_32 i;
-   png_size_t sum = 0;
-   int v;
-
-   png_ptr->try_row[0] = PNG_FILTER_VALUE_AVG;
-
-   for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
-        pp = png_ptr->prev_row + 1; i < bpp; i++)
-   {
-      v = *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
-
-      sum += (v < 128) ? v : 256 - v;
-   }
-
-   for (lp = png_ptr->row_buf + 1; i < row_bytes; i++)
-   {
-      v = *dp++ = (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2))
-          & 0xff);
-
-      sum += (v < 128) ? v : 256 - v;
-
-      if (sum > lmins)  /* We are already worse, don't continue. */
-        break;
-   }
-
-   return (sum);
-}
-
-static png_size_t /* PRIVATE */
-png_setup_paeth_row(png_structrp png_ptr, const png_uint_32 bpp,
-    const png_size_t row_bytes, const png_size_t lmins)
-{
-   png_bytep rp, dp, pp, cp, lp;
-   png_size_t i;
-   png_size_t sum = 0;
-   int v;
-
-   png_ptr->try_row[0] = PNG_FILTER_VALUE_PAETH;
-
-   for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
-       pp = png_ptr->prev_row + 1; i < bpp; i++)
-   {
-      v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
-
-      sum += (v < 128) ? v : 256 - v;
-   }
-
-   for (lp = png_ptr->row_buf + 1, cp = png_ptr->prev_row + 1; i < row_bytes;
-        i++)
-   {
-      int a, b, c, pa, pb, pc, p;
-
-      b = *pp++;
-      c = *cp++;
-      a = *lp++;
-
-      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
-
-      p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
-
-      v = *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
-
-      sum += (v < 128) ? v : 256 - v;
-
-      if (sum > lmins)  /* We are already worse, don't continue. */
-        break;
-   }
-
-   return (sum);
-}
-#endif /* WRITE_FILTER */
-
+#define PNG_MAXSUM (((png_uint_32)(-1)) >> 1)
+#define PNG_HISHIFT 10
+#define PNG_LOMASK ((png_uint_32)0xffffL)
+#define PNG_HIMASK ((png_uint_32)(~PNG_LOMASK >> PNG_HISHIFT))
 void /* PRIVATE */
 png_write_find_filter(png_structrp png_ptr, png_row_infop row_info)
 {
-#ifndef PNG_WRITE_FILTER_SUPPORTED
-   png_write_filtered_row(png_ptr, png_ptr->row_buf, row_info->rowbytes+1);
-#else
-   png_byte filter_to_do = png_ptr->do_filter;
-   png_bytep row_buf;
   png_bytep best_row;
-   png_uint_32 bpp;
-   png_size_t mins;
+#ifdef PNG_WRITE_FILTER_SUPPORTED
+   png_bytep prev_row, row_buf;
+   png_uint_32 mins, bpp;
+   png_byte filter_to_do = png_ptr->do_filter;
   png_size_t row_bytes = row_info->rowbytes;
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+   int num_p_filters = png_ptr->num_prev_filters;
+#endif

   png_debug(1, "in png_write_find_filter");

+#ifndef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+  if (png_ptr->row_number == 0 && filter_to_do == PNG_ALL_FILTERS)
+  {
+     /* These will never be selected so we need not test them. */
+     filter_to_do &= ~(PNG_FILTER_UP | PNG_FILTER_PAETH);
+  }
+#endif
+
   /* Find out how many bytes offset each pixel is */
   bpp = (row_info->pixel_depth + 7) >> 3;

-   row_buf = png_ptr->row_buf;
-   mins = PNG_SIZE_MAX - 256/* so we can detect potential overflow of the
-                               running sum */;
+   prev_row = png_ptr->prev_row;
+#endif
+   best_row = png_ptr->row_buf;
+#ifdef PNG_WRITE_FILTER_SUPPORTED
+   row_buf = best_row;
+   mins = PNG_MAXSUM;

   /* The prediction method we use is to find which method provides the
    * smallest value when summing the absolute values of the distances
@@ -2521,37 +2383,57 @@ png_write_find_filter(png_structrp png_ptr, png_row_infop row_info)
   /* We don't need to test the 'no filter' case if this is the only filter
    * that has been chosen, as it doesn't actually do anything to the data.
    */
-   best_row = png_ptr->row_buf;
-
-
   if ((filter_to_do & PNG_FILTER_NONE) != 0 && filter_to_do != PNG_FILTER_NONE)
   {
      png_bytep rp;
-      png_size_t sum = 0;
+      png_uint_32 sum = 0;
      png_size_t i;
      int v;

-      if (PNG_SIZE_MAX/128 <= row_bytes)
+      for (i = 0, rp = row_buf + 1; i < row_bytes; i++, rp++)
      {
-         for (i = 0, rp = row_buf + 1; i < row_bytes; i++, rp++)
-         {
-            /* Check for overflow */
-            if (sum > PNG_SIZE_MAX/128 - 256)
-               break;
-
-            v = *rp;
-            sum += (v < 128) ? v : 256 - v;
-         }
-      }
-      else /* Overflow is not possible */
-      {
-         for (i = 0, rp = row_buf + 1; i < row_bytes; i++, rp++)
-         {
-            v = *rp;
-            sum += (v < 128) ? v : 256 - v;
-         }
+         v = *rp;
+         sum += (v < 128) ? v : 256 - v;
      }

+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+      if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+      {
+         png_uint_32 sumhi, sumlo;
+         int j;
+         sumlo = sum & PNG_LOMASK;
+         sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK; /* Gives us some footroom */
+
+         /* Reduce the sum if we match any of the previous rows */
+         for (j = 0; j < num_p_filters; j++)
+         {
+            if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_NONE)
+            {
+               sumlo = (sumlo * png_ptr->filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+
+               sumhi = (sumhi * png_ptr->filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+            }
+         }
+
+         /* Factor in the cost of this filter (this is here for completeness,
+          * but it makes no sense to have a "cost" for the NONE filter, as
+          * it has the minimum possible computational cost - none).
+          */
+         sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_NONE]) >>
+             PNG_COST_SHIFT;
+
+         sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_NONE]) >>
+             PNG_COST_SHIFT;
+
+         if (sumhi > PNG_HIMASK)
+            sum = PNG_MAXSUM;
+
+         else
+            sum = (sumhi << PNG_HISHIFT) + sumlo;
+      }
+#endif
      mins = sum;
   }

@@ -2559,110 +2441,553 @@ png_write_find_filter(png_structrp png_ptr, png_row_infop row_info)
   if (filter_to_do == PNG_FILTER_SUB)
   /* It's the only filter so no testing is needed */
   {
-      (void) png_setup_sub_row(png_ptr, bpp, row_bytes, mins); 
-      best_row = png_ptr->try_row;
+      png_bytep rp, lp, dp;
+      png_size_t i;
+
+      for (i = 0, rp = row_buf + 1, dp = png_ptr->sub_row + 1; i < bpp;
+           i++, rp++, dp++)
+      {
+         *dp = *rp;
+      }
+
+      for (lp = row_buf + 1; i < row_bytes;
+         i++, rp++, lp++, dp++)
+      {
+         *dp = (png_byte)((int)*rp - (int)*lp);
+      }
+
+      best_row = png_ptr->sub_row;
   }

   else if ((filter_to_do & PNG_FILTER_SUB) != 0)
   {
-      png_size_t sum;
-      png_size_t lmins = mins;
+      png_bytep rp, dp, lp;
+      png_uint_32 sum = 0, lmins = mins;
+      png_size_t i;
+      int v;

-      sum = png_setup_sub_row(png_ptr, bpp, row_bytes, lmins); 
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+      /* We temporarily increase the "minimum sum" by the factor we
+       * would reduce the sum of this filter, so that we can do the
+       * early exit comparison without scaling the sum each time.
+       */
+      if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+      {
+         int j;
+         png_uint_32 lmhi, lmlo;
+         lmlo = lmins & PNG_LOMASK;
+         lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
+
+         for (j = 0; j < num_p_filters; j++)
+         {
+            if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_SUB)
+            {
+               lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+
+               lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+            }
+         }
+
+         lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
+             PNG_COST_SHIFT;
+
+         lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
+             PNG_COST_SHIFT;
+
+         if (lmhi > PNG_HIMASK)
+            lmins = PNG_MAXSUM;
+
+         else
+            lmins = (lmhi << PNG_HISHIFT) + lmlo;
+      }
+#endif
+
+      for (i = 0, rp = row_buf + 1, dp = png_ptr->sub_row + 1; i < bpp;
+           i++, rp++, dp++)
+      {
+         v = *dp = *rp;
+
+         sum += (v < 128) ? v : 256 - v;
+      }
+
+      for (lp = row_buf + 1; i < row_bytes;
+         i++, rp++, lp++, dp++)
+      {
+         v = *dp = (png_byte)((int)*rp - (int)*lp);
+
+         sum += (v < 128) ? v : 256 - v;
+
+         if (sum > lmins)  /* We are already worse, don't continue. */
+            break;
+      }
+
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+      if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+      {
+         int j;
+         png_uint_32 sumhi, sumlo;
+         sumlo = sum & PNG_LOMASK;
+         sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
+
+         for (j = 0; j < num_p_filters; j++)
+         {
+            if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_SUB)
+            {
+               sumlo = (sumlo * png_ptr->inv_filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+
+               sumhi = (sumhi * png_ptr->inv_filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+            }
+         }
+
+         sumlo = (sumlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
+             PNG_COST_SHIFT;
+
+         sumhi = (sumhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
+             PNG_COST_SHIFT;
+
+         if (sumhi > PNG_HIMASK)
+            sum = PNG_MAXSUM;
+
+         else
+            sum = (sumhi << PNG_HISHIFT) + sumlo;
+      }
+#endif

      if (sum < mins)
      {
         mins = sum;
-         best_row = png_ptr->try_row;
-         if (png_ptr->tst_row != NULL)
-         {
-            png_ptr->try_row = png_ptr->tst_row;
-            png_ptr->tst_row = best_row;
-         }
+         best_row = png_ptr->sub_row;
      }
   }

   /* Up filter */
   if (filter_to_do == PNG_FILTER_UP)
   {
-      (void) png_setup_up_row(png_ptr, row_bytes, mins);
-      best_row = png_ptr->try_row;
+      png_bytep rp, dp, pp;
+      png_size_t i;
+
+      for (i = 0, rp = row_buf + 1, dp = png_ptr->up_row + 1,
+          pp = prev_row + 1; i < row_bytes;
+          i++, rp++, pp++, dp++)
+      {
+         *dp = (png_byte)((int)*rp - (int)*pp);
+      }
+
+      best_row = png_ptr->up_row;
   }

   else if ((filter_to_do & PNG_FILTER_UP) != 0)
   {
-      png_size_t sum;
-      png_size_t lmins = mins;
+      png_bytep rp, dp, pp;
+      png_uint_32 sum = 0, lmins = mins;
+      png_size_t i;
+      int v;

-      sum = png_setup_up_row(png_ptr, row_bytes, lmins); 
+
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+      if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+      {
+         int j;
+         png_uint_32 lmhi, lmlo;
+         lmlo = lmins & PNG_LOMASK;
+         lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
+
+         for (j = 0; j < num_p_filters; j++)
+         {
+            if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_UP)
+            {
+               lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+
+               lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+            }
+         }
+
+         lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_UP]) >>
+             PNG_COST_SHIFT;
+
+         lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_UP]) >>
+             PNG_COST_SHIFT;
+
+         if (lmhi > PNG_HIMASK)
+            lmins = PNG_MAXSUM;
+
+         else
+            lmins = (lmhi << PNG_HISHIFT) + lmlo;
+      }
+#endif
+
+      for (i = 0, rp = row_buf + 1, dp = png_ptr->up_row + 1,
+          pp = prev_row + 1; i < row_bytes; i++)
+      {
+         v = *dp++ = (png_byte)((int)*rp++ - (int)*pp++);
+
+         sum += (v < 128) ? v : 256 - v;
+
+         if (sum > lmins)  /* We are already worse, don't continue. */
+            break;
+      }
+
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+      if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+      {
+         int j;
+         png_uint_32 sumhi, sumlo;
+         sumlo = sum & PNG_LOMASK;
+         sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
+
+         for (j = 0; j < num_p_filters; j++)
+         {
+            if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_UP)
+            {
+               sumlo = (sumlo * png_ptr->filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+
+               sumhi = (sumhi * png_ptr->filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+            }
+         }
+
+         sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_UP]) >>
+             PNG_COST_SHIFT;
+
+         sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_UP]) >>
+             PNG_COST_SHIFT;
+
+         if (sumhi > PNG_HIMASK)
+            sum = PNG_MAXSUM;
+
+         else
+            sum = (sumhi << PNG_HISHIFT) + sumlo;
+      }
+#endif

      if (sum < mins)
      {
         mins = sum;
-         best_row = png_ptr->try_row;
-         if (png_ptr->tst_row != NULL)
-         {
-            png_ptr->try_row = png_ptr->tst_row;
-            png_ptr->tst_row = best_row;
-         }
+         best_row = png_ptr->up_row;
      }
   }

   /* Avg filter */
   if (filter_to_do == PNG_FILTER_AVG)
   {
-      (void) png_setup_avg_row(png_ptr, bpp, row_bytes, mins);
-      best_row = png_ptr->try_row;
+      png_bytep rp, dp, pp, lp;
+      png_uint_32 i;
+
+      for (i = 0, rp = row_buf + 1, dp = png_ptr->avg_row + 1,
+           pp = prev_row + 1; i < bpp; i++)
+      {
+         *dp++ = (png_byte)((int)*rp++ - ((int)*pp++ / 2));
+      }
+
+      for (lp = row_buf + 1; i < row_bytes; i++)
+      {
+         *dp++ =
+             (png_byte)((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2));
+      }
+      best_row = png_ptr->avg_row;
   }

   else if ((filter_to_do & PNG_FILTER_AVG) != 0)
   {
-      png_size_t sum;
-      png_size_t lmins = mins;
+      png_bytep rp, dp, pp, lp;
+      png_uint_32 sum = 0, lmins = mins;
+      png_size_t i;
+      int v;

-      sum= png_setup_avg_row(png_ptr, bpp, row_bytes, lmins);
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+      if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+      {
+         int j;
+         png_uint_32 lmhi, lmlo;
+         lmlo = lmins & PNG_LOMASK;
+         lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
+
+         for (j = 0; j < num_p_filters; j++)
+         {
+            if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_AVG)
+            {
+               lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+
+               lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+            }
+         }
+
+         lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_AVG]) >>
+             PNG_COST_SHIFT;
+
+         lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_AVG]) >>
+             PNG_COST_SHIFT;
+
+         if (lmhi > PNG_HIMASK)
+            lmins = PNG_MAXSUM;
+
+         else
+            lmins = (lmhi << PNG_HISHIFT) + lmlo;
+      }
+#endif
+
+      for (i = 0, rp = row_buf + 1, dp = png_ptr->avg_row + 1,
+           pp = prev_row + 1; i < bpp; i++)
+      {
+         v = *dp++ = (png_byte)((int)*rp++ - ((int)*pp++ / 2));
+
+         sum += (v < 128) ? v : 256 - v;
+      }
+
+      for (lp = row_buf + 1; i < row_bytes; i++)
+      {
+         v = *dp++ =
+             (png_byte)(((int)*rp++ - ((int)*pp++ + (int)*lp++) / 2));
+
+         sum += (v < 128) ? v : 256 - v;
+
+         if (sum > lmins)  /* We are already worse, don't continue. */
+            break;
+      }
+
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+      if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+      {
+         int j;
+         png_uint_32 sumhi, sumlo;
+         sumlo = sum & PNG_LOMASK;
+         sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
+
+         for (j = 0; j < num_p_filters; j++)
+         {
+            if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_NONE)
+            {
+               sumlo = (sumlo * png_ptr->filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+
+               sumhi = (sumhi * png_ptr->filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+            }
+         }
+
+         sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_AVG]) >>
+             PNG_COST_SHIFT;
+
+         sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_AVG]) >>
+             PNG_COST_SHIFT;
+
+         if (sumhi > PNG_HIMASK)
+            sum = PNG_MAXSUM;
+
+         else
+            sum = (sumhi << PNG_HISHIFT) + sumlo;
+      }
+#endif

      if (sum < mins)
      {
         mins = sum;
-         best_row = png_ptr->try_row;
-         if (png_ptr->tst_row != NULL)
-         {
-            png_ptr->try_row = png_ptr->tst_row;
-            png_ptr->tst_row = best_row;
-         }
+         best_row = png_ptr->avg_row;
      }
   }

   /* Paeth filter */
   if ((filter_to_do == PNG_FILTER_PAETH) != 0)
   {
-      (void) png_setup_paeth_row(png_ptr, bpp, row_bytes, mins);
-      best_row = png_ptr->try_row;
+      png_bytep rp, dp, pp, cp, lp;
+      png_size_t i;
+
+      for (i = 0, rp = row_buf + 1, dp = png_ptr->paeth_row + 1,
+          pp = prev_row + 1; i < bpp; i++)
+      {
+         *dp++ = (png_byte)((int)*rp++ - (int)*pp++);
+      }
+
+      for (lp = row_buf + 1, cp = prev_row + 1; i < row_bytes; i++)
+      {
+         int a, b, c, pa, pb, pc, p;
+
+         b = *pp++;
+         c = *cp++;
+         a = *lp++;
+
+         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
+
+         p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
+
+         *dp++ = (png_byte)((int)*rp++ - p);
+      }
+      best_row = png_ptr->paeth_row;
   }

   else if ((filter_to_do & PNG_FILTER_PAETH) != 0)
   {
-      png_size_t sum;
-      png_size_t lmins = mins;
+      png_bytep rp, dp, pp, cp, lp;
+      png_uint_32 sum = 0, lmins = mins;
+      png_size_t i;
+      int v;

-      sum = png_setup_paeth_row(png_ptr, bpp, row_bytes, lmins);
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+      if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+      {
+         int j;
+         png_uint_32 lmhi, lmlo;
+         lmlo = lmins & PNG_LOMASK;
+         lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
+
+         for (j = 0; j < num_p_filters; j++)
+         {
+            if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_PAETH)
+            {
+               lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+
+               lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+            }
+         }
+
+         lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_PAETH]) >>
+             PNG_COST_SHIFT;
+
+         lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_PAETH]) >>
+             PNG_COST_SHIFT;
+
+         if (lmhi > PNG_HIMASK)
+            lmins = PNG_MAXSUM;
+
+         else
+            lmins = (lmhi << PNG_HISHIFT) + lmlo;
+      }
+#endif
+
+      for (i = 0, rp = row_buf + 1, dp = png_ptr->paeth_row + 1,
+          pp = prev_row + 1; i < bpp; i++)
+      {
+         v = *dp++ = (png_byte)((int)*rp++ - (int)*pp++);
+
+         sum += (v < 128) ? v : 256 - v;
+      }
+
+      for (lp = row_buf + 1, cp = prev_row + 1; i < row_bytes; i++)
+      {
+         int a, b, c, pa, pb, pc, p;
+
+         b = *pp++;
+         c = *cp++;
+         a = *lp++;
+
+#ifndef PNG_SLOW_PAETH
+         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
+         p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
+#else /* SLOW_PAETH */
+         p = a + b - c;
+         pa = abs(p - a);
+         pb = abs(p - b);
+         pc = abs(p - c);
+
+         if (pa <= pb && pa <= pc)
+            p = a;
+
+         else if (pb <= pc)
+            p = b;
+
+         else
+            p = c;
+#endif /* SLOW_PAETH */
+
+         v = *dp++ = (png_byte)((int)*rp++ - p);
+
+         sum += (v < 128) ? v : 256 - v;
+
+         if (sum > lmins)  /* We are already worse, don't continue. */
+            break;
+      }
+
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+      if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+      {
+         int j;
+         png_uint_32 sumhi, sumlo;
+         sumlo = sum & PNG_LOMASK;
+         sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
+
+         for (j = 0; j < num_p_filters; j++)
+         {
+            if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_PAETH)
+            {
+               sumlo = (sumlo * png_ptr->filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+
+               sumhi = (sumhi * png_ptr->filter_weights[j]) >>
+                   PNG_WEIGHT_SHIFT;
+            }
+         }
+
+         sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_PAETH]) >>
+             PNG_COST_SHIFT;
+
+         sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_PAETH]) >>
+             PNG_COST_SHIFT;
+
+         if (sumhi > PNG_HIMASK)
+            sum = PNG_MAXSUM;
+
+         else
+            sum = (sumhi << PNG_HISHIFT) + sumlo;
+      }
+#endif

      if (sum < mins)
      {
-         mins = sum;
-         best_row = png_ptr->try_row;
-         if (png_ptr->tst_row != NULL)
-         {
-            png_ptr->try_row = png_ptr->tst_row;
-            png_ptr->tst_row = best_row;
-         }
+         best_row = png_ptr->paeth_row;
      }
   }
+#endif /* WRITE_FILTER */

   /* Do the actual writing of the filtered row data from the chosen filter. */
   png_write_filtered_row(png_ptr, best_row, row_info->rowbytes+1);

+#ifdef PNG_WRITE_FILTER_SUPPORTED
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+   /* Save the type of filter we picked this time for future calculations */
+   if (png_ptr->num_prev_filters > 0)
+   {
+      int j;
+
+      for (j = 1; j < num_p_filters; j++)
+      {
+         png_ptr->prev_filters[j] = png_ptr->prev_filters[j - 1];
+      }
+
+      png_ptr->prev_filters[j] = best_row[0];
+   }
+#endif
 #endif /* WRITE_FILTER */
 }

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

 VisualStudio instructions

-libpng version 1.6.18beta06 - June 1, 2015
+libpng version 1.6.17 - March 26, 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 1.6.18beta06 - June 1, 2015
+ * libpng version 1.6.17 - March 26, 2015
 *
 * Copyright (c) 1998-2011 Glenn Randers-Pehrson
 *
--- a/scripts/README.txt
+++ b/scripts/README.txt
@@ -1,9 +1,9 @@

-Makefiles for  libpng version 1.6.18beta06 - June 1, 2015
+Makefiles for  libpng version 1.6.17 - March 26, 2015

 pnglibconf.h.prebuilt       =>  Stores configuration settings
 makefile.linux    =>  Linux/ELF makefile
-                       (gcc, creates libpng16.so.16.1.6.18beta06)
+                       (gcc, creates libpng16.so.16.1.6.17)
 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.16.1.6.18beta06)
+                       creates libpng16.so.16.1.6.17)
 makefile.sgi      =>  Silicon Graphics IRIX makefile (cc, creates static lib)
 makefile.solaris  =>  Solaris 2.X makefile (gcc,
-                       creates libpng16.so.16.1.6.18beta06)
+                       creates libpng16.so.16.1.6.17)
 makefile.so9      =>  Solaris 9 makefile (gcc,
-                       creates libpng16.so.16.1.6.18beta06)
+                       creates libpng16.so.16.1.6.17)
 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 1.6.18beta06"
+PNG_DFN ";Version 1.6.17"

 #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=1.6.18beta06
+version=1.6.17
 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: 1.6.18beta06
+Version: 1.6.17
 Libs: -L${libdir} -lpng16
 Cflags: -I${includedir}
--- a/scripts/makefile.cegcc
+++ b/scripts/makefile.cegcc
@@ -23,7 +23,7 @@

 VERMAJ = 1
 VERMIN = 6
-VERMIC = 18
+VERMIC = 17
 VER = $(VERMAJ).$(VERMIN).$(VERMIC)
 NAME = libpng
 PACKAGE = $(NAME)-$(VER)
--- a/scripts/makefile.linux
+++ b/scripts/makefile.linux
@@ -10,7 +10,7 @@
 # Library name:
 LIBNAME = libpng16
 PNGMAJ = 16
-RELEASE = 18
+RELEASE = 17

 # Shared library names:
 LIBSO=$(LIBNAME).so
--- a/scripts/makefile.msys
+++ b/scripts/makefile.msys
@@ -18,7 +18,7 @@ exec_prefix=$(prefix)
 # Library name:
 LIBNAME = libpng16
 PNGMAJ = 16
-RELEASE = 18
+RELEASE = 17

 # Shared library names:
 LIBSO=$(LIBNAME).dll
--- a/scripts/makefile.ne12bsd
+++ b/scripts/makefile.ne12bsd
@@ -17,7 +17,7 @@ INCSDIR=${LOCALBASE}/include/libpng16

 LIB=	png16
 SHLIB_MAJOR=	0
-SHLIB_MINOR=	1.6.18beta06
+SHLIB_MINOR=	1.6.17
 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=	1.6.18beta06
+SHLIB_MINOR=	1.6.17
 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=	1.6.18beta06
+SHLIB_MINOR=	1.6.17

 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
-#                 deprecated - use the png_set_option API.
+#                 deprectated - 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
--- a/scripts/pnglibconf.h.prebuilt
+++ b/scripts/pnglibconf.h.prebuilt
@@ -1,8 +1,8 @@
-/* libpng 1.6.18beta06 STANDARD API DEFINITION */
+/* libpng 1.6.17 STANDARD API DEFINITION */

 /* pnglibconf.h - library build configuration */

-/* Libpng version 1.6.18beta06 - June 1, 2015 */
+/* Libpng version 1.6.17 - March 26, 2015 */

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

@@ -101,6 +101,8 @@
 #define PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
 #define PNG_SEQUENTIAL_READ_SUPPORTED
 #define PNG_SETJMP_SUPPORTED
+#define PNG_SET_CHUNK_CACHE_LIMIT_SUPPORTED
+#define PNG_SET_CHUNK_MALLOC_LIMIT_SUPPORTED
 #define PNG_SET_OPTION_SUPPORTED
 #define PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
 #define PNG_SET_USER_LIMITS_SUPPORTED
--- a/scripts/symbols.def
+++ b/scripts/symbols.def
@@ -1,4 +1,4 @@
-;Version 1.6.18beta06
+;Version 1.6.17
 ;--------------------------------------------------------------
 ; LIBPNG symbol list as a Win32 DEF file
 ; Contains all the symbols that can be exported from libpng