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pgmtopbm.1
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1994-08-27
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pgmtopbm(1) USER COMMANDS pgmtopbm(1)
NAME
pgmtopbm - convert a portable graymap into a portable bitmap
SYNOPSIS
pgmtopbm [-floyd|-fs|-threshold [-value _✓v_✓a_✓l] [_✓p_✓g_✓m_✓f_✓i_✓l_✓e]
DESCRIPTION
Reads a portable graymap as input. Produces a portable bit-
map 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). Also available are sim-
ple 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 _✓p_✓n_✓m_✓c_✓o_✓n_✓v_✓o_✓l 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 pre-
fix.
REFERENCES
The only reference you need for this stuff is "Digital Half-
toning" 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.
Sun Release 4.0 Last change: 26 July 1988 1