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Ppmtopgm User Manual
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ppmtopgm
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Updated: 10 April 2000
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Table Of Contents
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NAME
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ppmtopgm - convert a PPM image to a PGM image
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SYNOPSIS
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\fBppmtopgm\fR
[\fIppmfile\fR]
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DESCRIPTION
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This program is part of Netpbm.
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\fBppmtopgm\fR reads a PPM as input and produces a PGM as output.
The output is a "black and white" rendering of the original
image, as in a black and white photograph.  The quantization formula
\fBppmtopgm\fR uses is g = .299 r + .587 g + .114 b.
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Note that although there is a \fBpgmtoppm\fR program, it is not
necessary for simple conversions from pgm to ppm , because any ppm
program can read pgm (and pbm ) files automatically.  \fBpgmtoppm\fR
is for colorizing a pgm file.  Also, see \fBppmtorgb3\fR for a
different way of converting color to gray.  And \fBppmdist\fR
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.
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QUOTE
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.DS L
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.
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SEE ALSO
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\fBpgmtoppm\fR,
\fBppmtorgb3\fR,
\fBrgb3toppm\fR,
\fBppmdist\fR,
\fBppm\fR,
\fBpgm\fR
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AUTHOR
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Copyright (C) 1989 by Jef Poskanzer.
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\l'5i'
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Table Of Contents
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