1Ppmtopgm User Manual(0)                                Ppmtopgm User Manual(0)
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NAME

6       ppmtopgm - convert a PPM image to a PGM image
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SYNOPSIS

10       ppmtopgm
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12       [ppmfile]
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DESCRIPTION

16       This program is part of Netpbm(1).
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18       ppmtopgm reads a PPM as input and produces a PGM as output.  The output
19       is a 'black and white' rendering of the original image, as in  a  black
20       and  white  photograph.   The quantization formula ppmtopgm uses is g =
21       .299 r + .587 g + .114 b.
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23       Note that although there is a pgmtoppm program, it is not necessary for
24       simple  conversions  from pgm to ppm , because any ppm program can read
25       pgm (and pbm ) files automatically.  pgmtoppm is for colorizing  a  pgm
26       file.   Also,  see ppmtorgb3 for a different way of converting color to
27       gray.  And ppmdist generates a grayscale image from a color image,  but
28       in  a  way that makes it easy to differentiate the original colors, not
29       necessarily a way that looks like a black and white photograph.
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QUOTE

33       Cold-hearted orb that rules the night
34       Removes the colors from our sight
35       Red is gray, and yellow white
36       But we decide which is right
37       And which is a quantization error.
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SEE ALSO

41       pgmtoppm(1), ppmtorgb3(1), rgb3toppm(1), ppmdist(1), ppm(1), pgm(1)
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AUTHOR

45       Copyright (C) 1989 by Jef Poskanzer.
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49netpbm documentation             10 April 2000         Ppmtopgm User Manual(0)