** PNMTOPNG / PNGTOPNM
** version 2.38 - 16 June 2002

This is another in a set of semi-official bug-fix/enhancement releases.
I sort of took over maintenance of this package while Willem was on an
extended bike trip several years ago, and for now I'm continuing with
periodic, small updates.  (The code really should be rewritten to avoid
directly messing with libpng's internal structures, but I haven't yet
found time to do that.)

Brief changelog:

  2.37   - (March 1998) never publicly released, partly because Willem had
           hoped to quiet gcc's "<var> might be clobbered by `longjmp'"

  2.37.2 - fixed gcc "clobber" warnings; under Solaris, they resulted in
           stack corruption even when there was no error in the image files
           or libraries

  2.37.3 - fixed a minor bug with respect to error exits; generally cleaner
           error exits (close files, etc.)

  2.37.4 - fixed a bug that caused 16-shade grayscale images to be written
           as 8-bit grayscale instead of (smaller) 4-bit colormapped images
           (bug report, analysis and fix by Rafal Rzeczkowski); added support
           for the new/upcoming pbmplus release (based on 1999-11-28 beta).

  2.37.5 - fixed a bug in -transparent handling (pnmtopng no longer chooses
           an approximate color if the specified one isn't present); quieted
           a gcc warning in the non-16-bit version; added optional support
           for warning-level return codes (define PNMTOPNG_WARNING_LEVEL 2
           to enable) to pnmtopng

  2.37.6 - fixed a bug in -background handling for low-bit-depth grayscale
           images; renamed version.h to pnmtopng_version.h

  2.38   - forced explicit binary mode on stdin/stdout for DOS-like OSes;
           added same (optional) support for warning-level return codes to
           pngtopnm (see 2.37.5 above); plugged some memory leaks; documented
           palette-remapping code better; added support for custom (ordered)
           palette (new -palette option); added some checks for malloc()
           failure; extended syntax of text-comment files by allowing blank
           lines and keywords on separate lines from main text (tenthumbs at
           cybernex.net); abandoned silly "ultra-minor" version number

                   -- [end of Greg Roelofs commentary] --


The utilities pnmtopng and pngtopnm are based on other pbm tools and require
the libraries included in the pbmplus/netpbm package. Also required are the
png library and the zlib compression library.

These can be found at:
	ftp://swrinde.nde.swri.edu/pub/png/src/libpng-*
	ftp://swrinde.nde.swri.edu/pub/png/src/zlib-*
	ftp://ftp.x.org/contrib/utilities/netpbm-1mar1994*
or see
	http://www.libpng.org/pub/png/apps/pnmtopng.html
	http://www.libpng.org/pub/png/libpng.html
	http://www.zlib.org/
	http://netpbm.sourceforge.net/
	http://www.acme.com/software/pbmplus/	[update coming someday?]

To compile and install, a makefile is provided. Do check the directories
where you have put the required libraries. Then either accommodate the 
makefile or make links from generic names (e.g., zlib) to version-specific
directories (e.g., zlib-1.1.4), which is the recommended way.

For testing purposes, have a look at the test-set PngSuite.tar.gz, which
contains a small test-image for every PNG color type and for most PNG chunk
types. It can be found at:
	http://www.schaik.com/pngsuite/pngsuite.html
	ftp://swrinde.nde.swri.edu/pub/png/images/suite/

Other web pages with PNG images are at:
	http://www.libpng.org/pub/png/png-textures.html
	http://www.libpng.org/pub/png/pngs-img.html
	http://www.libpng.org/pub/png/pngpic2.html
	http://www.libpng.org/pub/png/colorcube/
	http://www.libpng.org/pub/png/pngmisc.html#images

------
Alexander Lehmann <lehmann@usa.net>
Willem van Schaik <willem@schaik.com>
Greg Roelofs <newt@pobox.com>