usage            1057 contrib/libtests/pngunknown.c usage(const char *program, const char *reason)
usage             169 contrib/pngminus/png2pnm.c void usage()
usage             167 contrib/pngminus/pnm2png.c void usage()
usage              25 contrib/tools/cvtcolor.c usage(const char *prog)
usage            3674 contrib/tools/pngfix.c usage(const char *prog)