# ppmtopgm

Updated: 10 April 2000
Index

## 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,ppmtorgb3,rgb3toppm,ppmdist,ppm,pgm

## AUTHOR

Copyright (C) 1989 by Jef Poskanzer.

## Index

NAME
SYNOPSIS
DESCRIPTION
QUOTE
SEE ALSO
AUTHOR