NAME¶
ppmtopgm - convert a portable pixmap into a portable graymap
SYNOPSIS¶
ppmtopgm [
ppmfile]
DESCRIPTION¶
Reads 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
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.
QUOTE¶
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.
SEE ALSO¶
pgmtoppm(1),
ppmtorgb3(1),
rgb3toppm(1),
ppmdist(1),
ppm(5),
pgm(5)
AUTHOR¶
Copyright (C) 1989 by Jef Poskanzer.