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pgmtopbm.man
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1995-03-17
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pgmtopbm(1) AMIGA (26 July 1988) pgmtopbm(1)
NAME
pgmtopbm - convert a portable graymap into a portable bitmap
SYNOPSIS
pgmtopbm [-floyd|-fs|-threshold |-dither8|-d8|-cluster3 |-
c3|-cluster4|-c4 |-cluster8|-c8] [-value val] [pgmfile]
DESCRIPTION
Reads a portable graymap as input. Produces a portable
bitmap as output.
Note that there is no pbmtopgm converter, because any pgm
program can read pbm files automagically.
OPTIONS
The default quantization method is boustrophedonic Floyd-
Steinberg error diffusion (-floyd or -fs). Also available
are simple thresholding (-threshold); Bayer's ordered dither
(-dither8) with a 16x16 matrix; and three different sizes of
45-degree clustered-dot dither (-cluster3, -cluster4, -
cluster8).
Floyd-Steinberg will almost always give the best looking
results; however, looking good is not always what you want.
For instance, thresholding can be used in a pipeline with
the pnmconvol tool, for tasks like edge and peak detection.
And clustered-dot dithering gives a newspaper-ish look, a
useful special effect.
The -value flag alters the thresholding value for Floyd-
Steinberg and simple thresholding. It should be a real
number between 0 and 1. Above 0.5 means darker images;
below 0.5 means lighter.
All flags can be abbreviated to their shortest unique
prefix.
REFERENCES
The only reference you need for this stuff is "Digital
Halftoning" by Robert Ulichney, MIT Press, ISBN 0-262-
21009-6.
SEE ALSO
pbmreduce(1), pgm(5), pbm(5), pnmconvol(1)
AUTHOR
Copyright (C) 1989 by Jef Poskanzer.
Page 1 (printed 10/19/91)