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diff --git a/upstream/mageia-cauldron/man1/pamditherbw.1 b/upstream/mageia-cauldron/man1/pamditherbw.1 new file mode 100644 index 00000000..c60ace76 --- /dev/null +++ b/upstream/mageia-cauldron/man1/pamditherbw.1 @@ -0,0 +1,223 @@ +\ +.\" This man page was generated by the Netpbm tool 'makeman' from HTML source. +.\" Do not hand-hack it! If you have bug fixes or improvements, please find +.\" the corresponding HTML page on the Netpbm website, generate a patch +.\" against that, and send it to the Netpbm maintainer. +.TH "Pamditherbw User Manual" 0 "10 May 2010" "netpbm documentation" + +.SH NAME + +pamditherbw - dither grayscale image to black and white + +.UN synopsis +.SH SYNOPSIS + +\fBpamditherbw\fP + +[\fB-floyd\fP | \fB-fs\fP +| \fB-atkinson\fP +| \fB-threshold\fP +| \fB-hilbert\fP +| \fB-dither8\fP | \fB-d8\fP | \fB-cluster3\fP +| \fB-c3\fP | \fB-cluster4\fP | \fB-c4\fP +| \fB-cluster8\fP | \fB-c8\fP] + +[\fB-value\fP \fIval\fP] + +[\fB-clump\fP \fIsize\fP] + +[\fB-randomseed=\fP\fIinteger\fP] + +[\fIpamfile\fP] +.PP +All options can be abbreviated to their shortest unique prefix. + +.UN description +.SH DESCRIPTION +.PP +This program is part of +.BR "Netpbm" (1)\c +\&. +.PP +\fBpamditherbw\fP dithers a grayscale image. Dithering means turning +each shade of gray into a pattern of black and white pixels that, from +a distance, look the same as the gray. +.PP +The input should be a PGM image or a PAM image of tuple type +GRAYSCALE. However, \fBpamditherbw\fP doesn't check, so if you feed +it e.g. a PPM image, it will produce arbitrary results (actually, it +just takes the first channel of whatever you give it and treats it as +if it represented gray levels). +.PP +The output is a PAM with tuple type BLACKANDWHITE. You can turn +this into a PBM (if you need to use it with an older program that doesn't +understand PAM) with \fBpamtopnm\fP. +.PP +To do the opposite of dithering, you can usually just scale the image +down and then back up again with \fBpamscale\fP, possibly smoothing or +blurring the result with \fBpnmsmooth\fP or \fBpnmconvol\fP. Or use +the special case program \fBpbmtopgm\fP. +.PP +To dither a color image (to reduce the number of pixel colors), +use \fBppmdither\fP. +.PP +Another way to convert a grayscale image to a black and white image +is thresholding. Thresholding is simply replacing each grayscale pixel +with a black or white pixel depending on whether its brightness is above or +below a threshold. That threshold might vary. Simple thresholding is a +degenerate case of dithering, so \fBpamditherbw\fP does very simple +thresholding with its \fB-threshold\fP option. But \fBpamthreshold\fP +does more sophisticated thresholding. +.PP +If all you want is to change a PGM image with maxval 1 to a PBM image, +\fBpamtopnm\fP will do that. + + +.UN options +.SH OPTIONS +.PP +In addition to the options common to all programs based on libnetpbm +(most notably \fB-quiet\fP, see +.UR index.html#commonoptions + Common Options +.UE +\&), \fBpamditherbw\fP recognizes the following +command line options: + +.UN quantmethod +.SS Quantization Method +.PP +The default quantization method is boustrophedonic Floyd-Steinberg +error diffusion (\fB-floyd\fP or \fB-fs\fP). +.PP +Also available are simple thresholding (\fB-threshold\fP); Bayer's +ordered dither (\fB-dither8\fP) with a 16x16 matrix; +.UR http://www.tinrocket.com/projects/programming/graphics/00158/ + Atkinson +.UE +\&; and three different sizes of 45-degree clustered-dot +dither (\fB-cluster3\fP, \fB-cluster4\fP, \fB-cluster8\fP). +.PP +A space filling curve halftoning method using the Hilbert curve is +also available (\fB-hilbert\fP). +.PP +Floyd-Steinberg or Atkinson will almost always give the best +looking results; however, looking good is not always what you want. +For instance, you can use thresholding in a pipeline with the +\fBpnmconvol\fP, for tasks such as edge and peak detection. And +clustered-dot dithering gives a newspaper-ish look, a useful special +effect. +.PP +Floyd-Steinberg is by far the more traditional, but +.UR http://www.tinrocket.com/projects/programming/graphics/00158/ + some claim +.UE +\& Atkinson works better. +.PP +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 +\fB-clump\fP option alters the number of pixels in a clump. 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: + +.nf + pamscale -xysize 2400 3000 image.pgm | pamditherbw -hilbert | \e + pamtopnm | pnmtops -scale 0.25 > image.ps + +.fi + +.UN otheropts +.SS Other Options + + + +.TP +\fB-value\fP +This option alters the thresholding value for Floyd-Steinberg, +Atkinson, and simple thresholding. It should be a real number between +0 and 1. Above 0.5 means darker images; below 0.5 means lighter. + +.TP +\fB-clump\fP +This option alters the number of pixels in a clump when the +Hilbert curve method is used. 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 lose some grey scale linearity. + +.TP +\fB-randomseed=\fP\fIinteger\fP +The Floyd-Steiberg and Atkinson methods use random numbers to +diffuse the error. This is the seed for the random number generator. +The other methods do not employ random numbers and ignore this option. +.sp +Use this to ensure you get the same image on separate invocations. +.sp +By default, \fBpamditherbw\fP uses a seed derived from the time of day +and process ID, which gives you fairly uncorrelated results in multiple +invocations. +.sp +This option was new in Netpbm 10.45 (December 2008). + + + + +.UN references +.SH REFERENCES +.PP +The only reference you need for this stuff is "Digital +Halftoning" by Robert Ulichney, MIT Press, ISBN 0-262-21009-6. +.PP +The Hilbert curve space filling method is taken from "Digital +Halftoning with Space Filling Curves" by Luiz Velho, Computer +Graphics Volume 25, Number 4, proceedings of SIGRAPH '91, page +81. ISBN 0-89791-436-8 + +.UN seealso +.SH SEE ALSO +.BR "pamtopnm" (1)\c +\&, +.BR "pgmtopgm" (1)\c +\&, +.BR "pbmtopgm" (1)\c +\&, +.BR "pamthreshold" (1)\c +\&, +.BR "pbmreduce" (1)\c +\&, +.BR "pnmconvol" (1)\c +\&, +.BR "pamscale" (1)\c +\&, +.BR "pam" (1)\c +\&, +.BR "pnm" (1)\c +\&, + +.UN history +.SH HISTORY +.PP +\fBpamditherbw\fP was new in Netpbm 10.23 (July 2004), but is +essentially the same program as \fBpgmtopbm\fP that has existed +practically since the beginning. \fBpamditherbw\fP differs from its +predecessor in that it properly adds brightnesses (using gamma +transformations; \fBpgmtopbm\fP just adds them linearly) and that it +accepts PAM input in addition to PGM and PBM and produces PAM output. +.PP +\fBpamditherbw\fP obsoletes \fBpgmtopbm\fP. +.PP +\fB-atkinson\fP was new in Netpbm 10.38 (March 2007). + +.UN author +.SH AUTHOR + +Copyright (C) 1989 by Jef Poskanzer. +.SH DOCUMENT SOURCE +This manual page was generated by the Netpbm tool 'makeman' from HTML +source. The master documentation is at +.IP +.B http://netpbm.sourceforge.net/doc/pamditherbw.html +.PP
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