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pgmtopbm.1
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1995-07-25
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3KB
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67 lines
ppppggggmmmmttttooooppppbbbbmmmm((((1111)))) XXXXEEEENNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((22226666 JJJJuuuullllyyyy 1111999988888888)))) ppppggggmmmmttttooooppppbbbbmmmm((((1111))))
NNNNAAAAMMMMEEEE
pgmtopbm - convert a portable graymap into a portable bitmap
SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
ppppggggmmmmttttooooppppbbbbmmmm [----ffffllllooooyyyydddd|----ffffssss|----tttthhhhrrrreeeesssshhhhoooolllldddd |----ddddiiiitttthhhheeeerrrr8888|----dddd8888|----cccclllluuuusssstttteeeerrrr3333 |----
cccc3333|----cccclllluuuusssstttteeeerrrr4444|----cccc4444 |----cccclllluuuusssstttteeeerrrr8888|----cccc8888] [----vvvvaaaalllluuuueeee _v_a_l] [_p_g_m_f_i_l_e]
DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
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.
OOOOPPPPTTTTIIIIOOOONNNNSSSS
The default quantization method is boustrophedonic Floyd-
Steinberg error diffusion (----ffffllllooooyyyydddd or ----ffffssss). Also available
are simple thresholding (----tttthhhhrrrreeeesssshhhhoooolllldddd); Bayer's ordered dither
(----ddddiiiitttthhhheeeerrrr8888) with a 16x16 matrix; and three different sizes of
45-degree clustered-dot dither (----cccclllluuuusssstttteeeerrrr3333, ----cccclllluuuusssstttteeeerrrr4444, ----
cccclllluuuusssstttteeeerrrr8888).
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 ----vvvvaaaalllluuuueeee 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.
RRRREEEEFFFFEEEERRRREEEENNNNCCCCEEEESSSS
The only reference you need for this stuff is "Digital
Halftoning" by Robert Ulichney, MIT Press, ISBN 0-262-
21009-6.
SSSSEEEEEEEE AAAALLLLSSSSOOOO
pbmreduce(1), pgm(5), pbm(5), pnmconvol(1)
AAAAUUUUTTTTHHHHOOOORRRR
Copyright (C) 1989 by Jef Poskanzer.
Page 1 (printed 9/7/93)