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PGMTOPBM.MAN
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pgmtopbm(1) Unix Programmer's Manual pgmtopbm(1)
NNNAAAMMMEEE
pgmtopbm - convert a portable graymap into a portable bitmap
SSSYYYNNNOOOPPPSSSIIISSS
pppgggmmmtttooopppbbbmmm [-fffllloooyyyddd|-fffsss|-ttthhhrrreeessshhhooolllddd|-dddiiittthhheeerrr888| [-vvvaaallluuueee _v_a_l] [_p_g_m_f_i_l_e]
DDDEEESSSCCCRRRIIIPPPTTTIIIOOONNN
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.
OOOPPPTTTIIIOOONNNSSS
The default quantization method is boustrophedonic Floyd-Steinberg error
diffusion (-fffllloooyyyddd). Also available are simple thresholding (-ttthhhrrreeessshhhooolllddd);
Bayer's ordered dither (-dddiiittthhheeerrr888) with a 16x16 matrix; and three
different sizes of 45-degree clustered-dot dither (-cccllluuusssttteeerrr333, ---cccllluuusssttteeerrr444,
---cccllluuusssttteeerrr888).
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 ---vvvaaallluuueee 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.
RRREEEFFFEEERRREEENNNCCCEEESSS
The only reference you need for this stuff is "Digital Halftoning" by
Robert Ulichney, MIT Press, ISBN 0-262-21009-6.
SSSEEEEEE AAALLLSSSOOO
pbmreduce(1), pgm(5), pbm(5), pnmconvol(1)
AAAUUUTTTHHHOOORRR
Copyright (C) 1989 by Jef Poskanzer.
26 July 1988 1