This demonstrates the use of PNG_USER_CONFIG, pngusr.h and pngusr.dfa

The makefile builds a minimal read-only decoder with embedded libpng

and zlib.

Specify the location of the zlib source (1.2.1 or later) as ZLIBSRC

on the make command line.

If you prefer to use the shared libraries, go to contrib/pngminus

and build the png2pnm application there.