Home
Main website
Display Sidebar
Hide Ads
Recent Changes
View Source:
pgmtopbm(1)
Edit
PageHistory
Diff
Info
LikePages
pgmtopbm !!!pgmtopbm NAME SYNOPSIS DESCRIPTION OPTIONS REFERENCES SEE ALSO AUTHOR ---- !!NAME pgmtopbm - convert a portable graymap into a portable bitmap !!SYNOPSIS __pgmtopbm__ [[__-floyd__|__-fs__|__-threshold__ |__-hilbert__ |__-dither8__|__-d8__|__-cluster3__ |__-c3__|__-cluster4__|__-c4__ |__-cluster8__|__-c8__] [[__-value__ ''val''] [[__-clump__ ''size''] [[''pgmfile''] !!DESCRIPTION Reads a portable graymap as input. Produces a portable bitmap as output. Note that there is no pbmtopgm converter. Any program that uses the Netpbm libraries to read PGM files, including virtually all programs in the Netpbm package, will read a PBM file automatically as if it were a PGM file. If you are using a less intelligent program that expects PGM input, use __pnmdepth__ to convert the PBM file to PGM. As long as the depth is greater than 1, __pnmdepth__ will generate PGM. This less intelligent program quite probably is also not intelligent enough to deal with general maxvals, so you should specify a depth of 255. !!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__). A space filling curve halftoning method using the Hilbert curve is also available. (__-hilbert__); 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. The Hilbert curve method is useful for processing images before display on devices that do not render individual pixels distinctly (like laser printers). This dithering method can give better results than the dithering usually done by the laser printers themselves. The __-clump__ flag alters the number of pixels in a clump. This is usually an integer between 2 and 100 (default 5). Smaller clump sizes smear the image less and are less grainy, but seem to loose some grey scale linearity. Typically a PGM image will have to be scaled to fit on a laser printer page (2400 x 3000 pixels for an A4 300 dpi page), and then dithered to a PBM image before being converted to a postscript file. A printing pipeline might look something like: pnmscale -xysize 2400 3000 image.pgm | pgmtopbm -hil | pnmtops -scale 0.25 __ All flags can be abbreviated to their shortest unique prefix. !!REFERENCES The only reference you need for this stuff is The Hilbert curve space filling method is taken from !!SEE ALSO pbmreduce(1), pgm(5), pbm(5), pnmconvol(1), pnmscale(1), pnmtops(1) !!AUTHOR Copyright (C) 1989 by Jef Poskanzer. ----
7 pages link to
pgmtopbm(1)
:
fstopgm(1)
pbmfilters(1)
pbmreduce(1)
pbmtopgm(1)
pgm(5)
pgmedge(1)
Man1p
This page is a man page (or other imported legacy content). We are unable to automatically determine the license status of this page.
