This demonstrates the use of PNG_USER_CONFIG and pngusr.h The makefile builds a minimal read-only progressive decoder with embedded libpng, zlib and your system's X library. Specify the location of the zlib source (1.2.1 or later) as ZLIBSRC on the make command line. Edit makefile if required, to find your X library and include files, then make ZLIBSRC=directory If you prefer to use the shared libraries, go to contrib/gregbook and build the rpng2-x application there.