pngcrush.c

It was built with libpng version 1.2.35, and is running with libpng version 1.2.35

/*
 * pngcrush.c - recompresses png files
 * Copyright (C) 1998-2002,2006-2009 Glenn Randers-Pehrson
 *                                   (glennrp at users.sf.net)
 * Copyright (C) 2005      Greg Roelofs
 *
 * The most recent version of pngcrush can be found at SourceForge in
 * http://pmt.sf.net/pngcrush/
 *
 * This program reads in a PNG image, and writes it out again, with the
 * optimum filter_method and zlib_level.  It uses brute force (trying
 * filter_method none, and libpng adaptive filtering, with compression
 * levels 3 and 9).  It does the most time-consuming method last in case
 * it turns out to be the best.
 *
 * Optionally, it can remove unwanted chunks or add gAMA, sRGB, bKGD,
 * tEXt/zTXt, and tRNS chunks.  It will remove some chunks such as gAMA,
 * cHRM, pHYs, and oFFs when their data fields contain all zero, which is a
 * mistake.
 *
 * Uses libpng and zlib.  This program was based upon libpng's pngtest.c.
 *
 * Thanks to Greg Roelofs for various bug fixes, suggestions, and
 * occasionally creating Linux executables.
 *
 * Thanks to Stephan Levavej for some helpful suggestions about gcc compiler
 * options and for a suggestion to increase the Z_MEM_LEVEL from default.
 *
 * Caution: there is another version of pngcrush that has been distributed by
 * Apple since mid-2008 as a part of the Xcode SDK.   Although it claims
 * to be pngcrush by Glenn Randers-Pehrson, it has additional options
 * "-iPhone" * and "-speed".  It writes files that have the PNG 8-byte signature
 * but are not valid PNG files, due to at least
 *
 *   o the presence of the CgBI chunk ahead of the IHDR chunk,
 *   o nonstandard deflate compression in IDAT, iCCP, and perhaps zTXt chunks,
 *   o the use of premultiplied alpha in color_type 6 files, and
 *   o the sample order is ARGB instead of RGBA in color_type 6 files.
 *
 * The original PNG file cannot be losslessly recovered from such files
 * because of the use of premultiplied alpha.
 *
 * Most PNG decoders will recognize the fact that an unknown critical
 * chunk "CgBI" is present and will immediately reject the file.
 *
 * It is said that the Xcode version of pngcrush is automatically applied
 * when PNG files are prepared for downloading to the iPhone unless the
 * user takes special measures to prevent it.
 *
 * I have not seen the source for the Xcode version of pngcrush.  All I
 * know, for now, is from running "strings -a" on a copy of the executable,
 * looking at two Xcode-PNG files, and reading Apple's patent application
 * <http://www.freepatentsonline.com/y2008/0177769.html>.
 *
 */

#define PNGCRUSH_VERSION "1.6.17"

/*
#define PNGCRUSH_COUNT_COLORS
*/

/*
 * NOTICES
 *
 * If you have modified this source, you may insert additional notices
 * immediately after this sentence.
 *
 * COPYRIGHT:
 *
 * Copyright (C) 1998-2002,2006-2009 Glenn Randers-Pehrson
 *                                   (glennrp at users.sf.net)
 * Copyright (C) 2005      Greg Roelofs
 *
 * DISCLAIMERS:
 *
 * The pngcrush computer program is supplied "AS IS".  The Author disclaims all
 * warranties, expressed or implied, including, without limitation, the
 * warranties of merchantability and of fitness for any purpose.  The
 * Author assumes no liability for direct, indirect, incidental, special,
 * exemplary, or consequential damages, which may result from the use of
 * the computer program, even if advised of the possibility of such damage.
 * There is no warranty against interference with your enjoyment of the
 * computer program or against infringement.  There is no warranty that my
 * efforts or the computer program will fulfill any of your particular purposes
 * or needs.  This computer program is provided with all faults, and the entire
 * risk of satisfactory quality, performance, accuracy, and effort is with
 * the user.
 *
 * LICENSE:
 *
 * Permission is hereby irrevocably granted to everyone to use, copy, modify,
 * and distribute this source code, or portions hereof, or executable programs
 * compiled from it, for any purpose, without payment of any fee, subject to
 * the following restrictions:
 *
 * 1. The origin of this source code must not be misrepresented.
 *
 * 2. Altered versions must be plainly marked as such and must not be
 *    misrepresented as being the original source.
 *
 * 3. This Copyright notice, disclaimer, and license may not be removed
 *    or altered from any source or altered source distribution.
 */

/* To do:
 *
 *   Reset CINFO to reflect decoder's required window size (instead of
 *   libz-1.1.3 encoder's required window size, which is 262 bytes larger).
 *   See discussion about zlib in png-list archives for April 2001.
 *
 *   Add a "pcRu" ancillary chunk that keeps track of the best method,
 *   methods already tried, and whether "loco crushing" was effective.
 *
 *   Try both transformed and untransformed colors when "-loco" is used.
 *
 *   Check for unused alpha channel and ok-to-reduce-depth.
 *   Take care that sBIT and bKGD data aren't lost when reducing images
 *   from truecolor to grayscale.
 *
 *   Rearrange palette to put most-used color first and transparent color
 *   second (see ImageMagick 5.1.1 and later).
 *
 *   Finish pplt (partial palette) feature.
 *
 *   Allow in-place file replacement or as a filter, as in
 *    "pngcrush -overwrite file.png"
 *    "pngcreator | pngcrush > output.png"
 *
 *   Use an alternate write function for the trial passes, that
 *   simply counts bytes rather than actually writing to a file, to save wear
 *   and tear on disk drives.
 *
 *   Remove text-handling and color-handling features and put
 *   those in a separate program or programs, to avoid unnecessary
 *   recompressing.
 *
 *   Move the Photoshop-fixing stuff into a separate program.
 *
 *   GRR: More generally (superset of previous 3 items):  split into separate
 *   "edit" and "crush" programs (or functions).  Former is fully libpng-
 *   aware, much like current pngcrush; latter makes little or no use of
 *   libpng (maybe IDAT-compression parts only?), instead handling virtually
 *   all chunks as opaque binary blocks that are copied to output file _once_,
 *   with IDATs alone replaced (either by best in-memory result or by original
 *   _data_ resplit into bigger IDATs, if pngcrush can't match/beat).  "edit"
 *   version should be similar to current code but more efficient:  make
 *   _one_ pass through args list, creating table of PNG_UINTs for removal;
 *   then make initial pass through PNG image, creating (in-order) table of
 *   all chunks (and byte offsets?) and marking each as "keep" or "remove"
 *   according to args table.  Can start with static table of ~20-30 slots,
 *   then double size & copy if run out of room:  still O(n) algorithm.
 */

#if 0 /* changelog */

Change log:

Version 1.6.17 (built with libpng-1.2.36and zlib-1.2.3.2)
  Defined TOO_FAR == 32767 in deflate.c (again).  The definition
    has continually been inadvertently omitted during zlib updates
    since pngcrush version 1.6.4.
  Revised handling of xcode files so at least we can get printout
    of IHDR values with "pngcrush -fix -n -v xcode.png".
  Moved ChangeLog.txt back into pngcrush.c so it does not get lost.
  Removed single quotes from the ChangeLog.

Version 1.6.16 (built with libpng-1.2.35 and zlib-1.2.3.2)
  Added -newtimestamp and -oldtimestamp options and changed
    default condition to timestamping the output file with
    the current time (i.e., -newtimestamp is default)
  If the -oldtimestamp option is used then the output file
    has the same timestamp as the input file.
  Added CgBI chunk detection.

Version 1.6.15 (built with libpng-1.2.35 and zlib-1.2.3.2)
  Fixes some missing typecasts on png_malloc() calls, patch from
    an anonymous reporter to the SourceForge bug tracker.
  Added -time_stamp option to change time stamping from default
    condition.

Version 1.6.14 (built with libpng-1.2.35 and zlib-1.2.3.2)
  Avoids CVE-2009-0040.

Version 1.6.12 (built with libpng-1.2.34 and zlib-1.2.3.2)

Version 1.6.11 (built with libpng-1.2.33 and zlib-1.2.3.2)
  Eliminated a memory leak in libpng with writing bad tEXt chunks.

Version 1.6.10 (built with libpng-1.2.31 and zlib-1.2.3.2)
  Add sTER chunk support.

Version 1.6.9 (built with libpng-1.2.31 and zlib-1.2.3.2)
  Updated cexcept.h to version 2.0.1
  Add missing curly brackets.

Version 1.6.8 (built with libpng-1.2.29 and zlib-1.2.3.2)
  Fixed bug with handling of -z and -zi options.

Version 1.6.7 (built with libpng-1.2.29 and zlib-1.2.3.2)
  Moved PNG_UINT_CHNK and some other defines from pngcrush.h to pngcrush.c
  Reject invalid color_type or bit_depth.

Version 1.6.6 (built with libpng-1.2.29 and zlib-1.2.3.2)
  Added dSIG support.  Pngcrush will not rewrite an image containing
  a dSIG chunk immediately following the IHDR chunk, unless the
  dSIG is explicitly removed with "-rem dSIG" or explicitly kept
  with "-keep dSIG".  In the latter case the saved dSIG chunks will
  become invalid if any changes are made to the datastream.

  Fixed bug in writing unknown chunks from the end_info_ptr.

Version 1.6.5 (built with libpng-1.2.29 and zlib-1.2.3.2)
  Discontinued adding a new gAMA chunk when writing sRGB chunk.

Version 1.6.4 (built with libpng-1.2.9rc1 and zlib-1.2.3)
  Fixed bug in handling of undocumented -trns_a option (Michal Politowski).
  Fixed bug with "nosave" handling of unknown chunks.

Version 1.6.3 (built with libpng-1.2.9beta11 and zlib-1.2.3)

  Fixed documentation of iTXt input (Shlomi Tal).
  Removed #define PNG_INTERNAL and provided prototypes for some
  internal libpng functions that are duplicated in pngcrush.c

Version 1.6.2 (built with libpng-1.2.8 and zlib-1.2.3)

  Fixed bug with "PNG_ROWBYTES" usage, introduced in version 1.6.0.
  The bug could cause a crash and only affects the "nolib" builds.

  Converted C++ style (// ...) comments to C style (/* ... */).

  Defined TOO_FAR == 32767 in deflate.c (again).  The definition was
  omitted from version 1.6.0 when zlib was upgraded to version 1.2.3.

Version 1.6.1 (distributed as 1.6.0, built with libpng-1.2.8 and zlib-1.2.3)

  Copied non-exported libpng functions from libpng into pngcrush, to make
  pngcrush play more nicely with shared libpng.  These are not compiled
  when a static library is being built with the bundled libpng and
  pngcrush.h is included.

Version 1.6.0-grr (built with libpng-1.2.4 and zlib-1.1.4pc or zlib-1.2.2)

  Moved ChangeLog out of pngcrush.c comments and into a separate file.

  Filtered pngcrush.c through "indent -kr" and "expand" for readability.

  Moved 550 lines of usage/help/copyright/license/version info to separate
  function(s) and cleaned up significantly.

  Added some comments for ease of navigation and readability.

  Stripped out a bunch of ancient-libpng compatibility stuff.

  Defined PNG_UINT_* macros (pngcrush.h for now).

  Fixed unknown-chunk handling ("-rem alla" and "-rem gifx" now work).

  Created modified version of makefile that supports external zlib.

  Added support for methods using Z_RLE zlib strategy (zlib 1.2.x only).

  Documented -huffman option in usage screen.

  Added IDAT statistics to final per-file summary.

  Added utime() support to give output files same timestamps as input files.

Version 1.5.10 (built with libpng-1.2.4 and zlib-1.1.4pc)

  Fixed bug, introduced in 1.5.9, that caused defaults for method 0 to
  be used instead of copying the original image, when the original was
  already smallest.

Version 1.5.9 (built with libpng-1.2.4beta3 and zlib-1.1.4pc)

  Work around CPU timer wraparound at 2G microseconds.

  Upgraded zlib from 1.1.3 to 1.1.4.  Pngcrush is believed not to
  be vulnerable to the zlib-1.1.3 buffer-overflow bug.

  Choose the first instance of smallest IDAT instead of the last,
  for faster final recompression, suggested by TSamuel.

Version 1.5.8 (built with libpng-1.2.1)

  Added -trns_a option for entering a tRNS array.

Version 1.5.7 (built with libpng-1.2.0)

  Added setargv.obj to Makefile.msc to expand wildcards, e.g., *.png

  Use constant string "pngcrush" instead of argv[0] when appropriate.

  Only check stats for infile==outfile once per input file, or not at all
  if "-nofilecheck" option is present or if a directory was created.

  Fixed bugs with changing bit_depth of grayscale images.

Version 1.5.6 (built with libpng-1.0.12)

  Eliminated extra "Removed the cHNK chunk" messages generated by version
  1.5.5 when "-rem alla" or "-rem allb" is used.

  All unknown chunks including safe-to-copy chunks are now removed in
  response to the "-rem alla" or "-rem allb" options.

  Issue a warning if the user tries "-cc" option when it is not supported.

Version 1.5.5 (built with libpng-1.0.12)

  Reset reduce_to_gray and it_is_opaque flags prior to processing each
  image.

  Enable removal of safe-to-copy chunks that are being handled as unknown
  e.g., "-rem time".

Version 1.5.4 (built with libpng-1.0.11)

  Added 262 to the length of uncompressed data when calculating
  required_window_size, to account for zlib/deflate implementation.

  Added "-bit_depth n" to the help screen.

  Call png_set_packing() when increasing bit_depth to 2 or 4.

  Added warning about not overwriting an existing tRNS chunk.

  Reduced the memory usage

  Write 500K IDAT chunks even when system libpng is being used.

  Ignore all-zero cHRM chunks, with a warning.

Version 1.5.3 (built with libpng-1.0.9beta5)

  Added "-loco" option (writes MNG files with filter_method 64)

  "-dir" and "-ext" options are no longer mutually exclusive, e.g.:
  pngcrush -loco -dir Crushed -ext .mng *.png

Version 1.5.2 (built with libpng-1.0.9beta1)

  Added "-iccp" option.

  Increased the zlib memory level, which improves compression (typically
  about 1.3 percent for photos) at the expense of increased memory usage.

  Enabled the "-max max_idat_size" option, even when max_idat_size
  exceeds the default 1/2 megabyte size.

  Added missing "png_ptr" argument to png_error() call

  Added "-loco" option, to enable the LOCO color transformation
  (R->R-G, G, B->B-G) while writing a MNG with filter_method 64. Undo
  the transformation and write the regular PNG filter_method (0) if the
  MNG filter_method 64 is detected.

  Revised the "-help" output slightly and improved the "-version" output.

  The "-already[_crushed]" option is now ignored if the "-force" option
  is present or if chunks are being added, deleted, or modified.

  Improved "things_have_changed" behavior (now, when set in a particular
  file, it is not set for all remaining files)

Version 1.5.1 (built with libpng-1.0.8)

  Disabled color counting by default and made it controllable with new
  -cc and -no_cc commandline arguments.

  Added some #ifdef PNGCRUSH_COUNT_COLORS around code that needs it.

  Revised count_colors() attempting to avoid stack corruption that has
  been observed on RedHat 6.2

  Added the word "irrevocably" to the license and changed "without fee"
  to "without payment of any fee".

Version 1.5.0 (built with libpng-1.0.8)

  After encountering an image with a bad Photoshop iCCP chunk, pngcrush
  1.4.5 through 1.4.8 write sRGB and gAMA=45455 chunks in all
  remaining PNG files on the command line.  This has been fixed so the
  correction is only applied to the particular bad input file.

Version 1.4.8 (built with libpng-1.0.8rc1)

  Detect and remove all-opaque alpha channel.
  Detect and reduce all-gray truecolor images to grayscale.