Morphos port by Diego Casorran.

Note from uploader: pngrewrite is best used to preprocess pngs (8 bits depth or below)
 before processing them with further optimizers like PngCrush or OptiPng (both available
 on Morphos). Many thanks to Diego Casorran for doing this port and allowing me to
 spread it. Visit his homepage at http://amiga.sourceforge.net for more of his portings
 and feel free to donate on his PayPal account to keep him doing this great service to
 the Amiga and clones community.

  pngrewrite
   version 1.2.1  - 8 Feb 2003

  A quick and dirty utility to reduce unnecessarily large palettes 
  and bit depths in PNG image files.


  ** To compile in a unix-like environment, type something like:
  **   cc -o pngrewrite pngrewrite.c -lpng -lz -lm

  Web site: <http://www.pobox.com/~jason1/pngrewrite/>
  This program and source code may be used without restriction.

  Primary author: Jason Summers  <jason1@pobox.com>

  Contributing authors:

     Wayne Schlitt
       - Write grayscale images when possible
	   - Ability to sort palette by color usage
	   - Improved find_pal_entry performance

     Soren Anderson
	   - Changes to allow use in a unix-style pipeline
	   - Improved compatibility with MinGW and Cygwin      
	   - Maintain tIME chunks
  Pngrewrite will:  
  * Remove any unused palette entries, and write a palette that is only as    large as needed.  
  * Remove (collapse) any duplicate palette entries.  
  * Convert non-palette image to palette images, provided they contain no
    more than 256 different colors.
  * Write images as grayscale when possible.  
  * Move any colors with transparency to the beginning of the palette, and    write a tRNS chunk that is a small as possible.  
  * Reduce the bit-depth (bits per pixel) as much as possible.  All of this is just basic stuff that any respectable image
   writing program  should always do automatically, but for some reason, many of them do not.

  Under no circumstances does pngrewrite change the actual pixel colors, or
  background color, or transparency of the image. If it ever does, that's a
  bug.

  --WARNING--  
  This version of pngrewrite removes most extra (ancillary) information from
  the PNG file, such as text comments. Although this does make the file size 
  smaller, the removed information may sometimes be important. For that reason,
  you should only use pngrewrite on image that were created by you.  The only
  ancillary chunks that are NOT removed are:     
  gAMA  - Image gamma setting     
  sRGB  - srgb color space indicator	 
  tIME  - creation time
  pHYs  - physical pixel size
  bKGD and tRNS - Background color and transparency are maintained.
   The actual chunk may be modified according to the new color structure.
  If the original image was interlaced, the new one will also be interlaced.
  Pngrewrite will not work at all on images that have more than 256 colors.
  Colors with the same RGB values but a different level of transparency count as different colors.
  The background color counts as an extra color  if it does not occur in the image.
  It will also not work at all on images that have a color depth of 16 bits, since they cannot have a palette.
  This is a very inefficient program. It is (relatively) slow, and uses tons of memory. 
  To be specific, it uses about 5 bytes per pixel, no matter what the bit depth of the image is.
  This program is (hopefully) reasonably portable, and should compile
  without too much effort on most ANSI C compilers. It requires the libpng
  and zlib libraries.

 PERMSSN    UID  GID    PACKED    SIZE  RATIO     CRC       STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[generic]               104409  217696  48.0% -lh5- 1da8 Apr 26  2005 pngrewrite
[generic]                 1868    3827  48.8% -lh5- 6bc1 Jul 25 03:54 pngrewrite-mos.readme
[generic]                 7010   21045  33.3% -lh5- c232 Jul 24 15:38 pngrewrite.c
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total         3 files  113287  242568  46.7%            Jul 27 20:49