AC_ARG_WITH([system-pnglib], [ --with-system-pnglib use installed pnglib library]) AC_ARG_WITH([pnglib_libdir], [ --with-pnglib-libdir=DIR Specify directory where the png library (libpng.a) resides.]) AC_ARG_WITH([pnglib_include], [ --with-pnglib-include=DIR Specify the pnglib header files location.])