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Pbmreduce User Manual(0)						 Pbmreduce User Manual(0)

       pbmreduce - read a PBM image and reduce it N times

       pbmreduce [-floyd|-fs|-threshold] [-value val] N [pbmfile]

       You can abbreviate any option to its shortest unique prefix.

       This program is part of Netpbm(1)

       pbmreduce  reads  a  PBM  image	as input and reduces it by a factor of N, producing a PBM
       image as output.

       pbmreduce duplicates a lot of the functionality of pamditherbw;	you  could  do	something
       like pamscale | pamditherbw, but pbmreduce is a lot faster.

       You  can  use pbmreduce 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 resolution, say 300 dpi, and then reduce by a factor of three or so using  pbmre-
       duce.  You can even correct the brightness of an image, by using the -value option.

       By  default,  pbmreduce does the halftoning after the reduction via boustrophedonic Floyd-
       Steinberg error diffusion; however, you can use the -threshold option  to  specify  simple
       thresholding.  This gives better results when reducing line drawings.

       The  -value  option  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.

       pamenlarge(1) , pamscale(1) , pamditherbw(1) , pbm(1)

       Copyright (C) 1988 by Jef Poskanzer.

netpbm documentation			  02 August 1989		 Pbmreduce User Manual(0)
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