rgb3toppm - combine three PGM images (R, G, B) into one PPM image
redpgmfile greenpgmfile bluepgmfile
This program is part of Netpbm(1).
rgb3toppm reads three PGM images as input, taking each to represent one component (red, green, and blue) of a color image. It produces a PPM image as output.
Copyright (C) 1991 by Jef Poskanzer.