NAMEppmtopgm - convert a portable pixmap into a portable graymap
DESCRIPTIONReads a portable pixmap as input. Produces a portable graymap as output. The output is a "black and white" rendering of the original image, as in a black and white photograph. The quantization formula used is .299 r + .587 g + .114 b.
Note that although there is a
program, it is not necessary for simple conversions from pgm to ppm ,
because any ppm program can read pgm (and pbm ) files automatically.
is for colorizing a pgm file. Also, see
for a different way of converting color to gray. And
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.