rgb3toppm - combine three portable graymaps into one
portable pixmap
rgb3toppm redpgmfile greenpgmfile bluepgmfile
Reads three portable graymaps as input. Combines them and
produces one portable pixmap as output.
ppmtorgb3(1), pgmtoppm(1), ppmtopgm(1), ppm(5), pgm(5)
Copyright (C) 1991 by Jef Poskanzer.