pngzop_README.txt

/*
  This is the pngzop branch of the "pmt" tree.
  Code for supporting the "zopfli" compression method
  in PNG files will appear here.

  Eventually this collection of scripts might be incorporated
  into pngcrush.

  Copyright 2013 by Glenn Randers-Pehrson
  Released under the pngcrush license (which is equivalent to the libpng
  license plus required UCITA disclaimers). See DISCLAIMERS and LICENSE below.

  Usage:
  pngzop [-b|--blacken] [-d|--directory dir] [-e|--extension ext] *.png

  Input: *.png
  Output (default): *_pngzop.png (to overwrite the input, use "-e .png")

  Pngzop does the following:

    1. Preprocesses the input file(s) with pngcrush -reduce
       (and optionally -blacken to clean up "dirty" transparent pixels)

    2. Uses pngcrush to write 6 test files, with 5 PNG filters and adaptive
       filtering.

    3. Extracts the IDAT contents from each of the 6 files.

    4. Recompresses the IDAT contents with zopfli (25 iterations).

    5. Reassembles the PNG file using the smallest of the zopfli-compressed
       results.

    6. Postprocesses the PNG file with "pngfix" to optimize the windowBits
       field, to minimize memory use during later decompression.

  Pngzop requires zopfli, pngcrush (version 1.7.65 or later), zpipe (from the
  "examples" directory of the zlib-1.2.7 or later distribution,), pngfix
  (from the libpng-1.6.3 or later distribution), and "mkdir -p",
  along with these programs that should have been installed from their "C"
  sources along with this "pngzop" script:
 
         pngzop_get_ihdr.exe
         pngzop_get_idat.exe
         pngzop_get_iend.exe
         pngzop_zlib_to_idat.exe

  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.
*/