ppmtopgm - convert a portable pixmap into a portable graymap
Reads a portable pixmap as input. Produces a portable
graymap as output. The output is a
Note that although there is a pgmtoppm program, it is
not necessary for simple conversions from pgm to ppm ,
because any ppm program can read pgm (and pbm ) files
automatically. pgmtoppm is for colorizing a pgm file.
Also, see ppmtorgb3 for a different way of converting
color to gray. And ppmdist generates a grayscale
image from a color image, but in a way that makes it easy to
differentiate the original colors, not necessarily a way
that looks like a black and white photograph.
Cold-hearted orb that rules the night
Removes the colors from our sight
Red is gray, and yellow white
But we decide which is right
And which is a quantization error.
Copyright (C) 1989 by Jef Poskanzer.