ppmtorgb3 - separate a portable pixmap into three portable graymaps
Reads a portable pixmap as input. Writes three portable
graymaps as output, one each for red, green, and
The output filenames are constructed by taking the input
filename, stripping off any extension, and appending
rgb3toppm(1), ppmtopgm(1), pgmtoppm(1), ppm(5),
Copyright (C) 1991 by Jef Poskanzer.