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Top Forums Shell Programming and Scripting meaning of today=${1:-${today}} Post 302612741 by Vidhyaprakash on Monday 26th of March 2012 09:50:50 AM
Old 03-26-2012
thanks a lot balaje!!!!
 
Test Your Knowledge in Computers #844
Difficulty: Medium
Bittorent, Gnutella and other distributed file transfers systems use do not user peer-to-peer, by default.
True or False?

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pbmreduce(1)                                                  General Commands Manual                                                 pbmreduce(1)

NAME
pbmreduce - read a portable bitmap and reduce it N times SYNOPSIS
pbmreduce [-floyd|-fs|-threshold ] [-value val] N [pbmfile] DESCRIPTION
Reads a portable bitmap as input. Reduces it by a factor of N, and produces a portable bitmap as output. pbmreduce duplicates a lot of the functionality of pgmtopbm; you could do something like pnmscale | pgmtopbm, but pbmreduce is a lot faster. pbmreduce can be used to "re-halftone" an image. Let's say you have a scanner that only produces black&white, not grayscale, and it does a terrible job of halftoning (most b&w scanners fit this description). One way to fix the halftoning is to scan at the highest possible res- olution, say 300 dpi, and then reduce by a factor of three or so using pbmreduce. You can even correct the brightness of an image, by using the -value flag. OPTIONS
By default, the halftoning after the reduction is done via boustrophedonic Floyd-Steinberg error diffusion; however, the -threshold flag can be used to specify simple thresholding. This gives better results when reducing line drawings. The -value flag alters the thresholding value for all quantizations. 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. SEE ALSO
pnmenlarge(1), pnmscale(1), pgmtopbm(1), pbm(5) AUTHOR
Copyright (C) 1988 by Jef Poskanzer. 02 August 1989 pbmreduce(1)

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