PNG library:
------------
Included is version 0.96, also called 1.0 beta 6 (May 16 '97).
WARNING: this version is binary incompatible (but source
comparible) with earlier versions than 0.90. So, if you
already have linpng v0.89c or earlier, better replace it and
be prepared to recompile existing applications!!!! The
distribution is downloaded from:
    ftp://swrinde.nde.swri.edu/pub/png/src/libpng-0.96.tgz

The PNG library depends on the libz library. If your system
doesn't have this library already, it should be built as well.

more info about the PNG format: http://www.cdrom.com/pub/png/