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



NAME
       pbmreduce - read a PBM image and reduce it N times


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

       You can abbreviate any option to its shortest unique prefix.


DESCRIPTION
       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 reso-
       lution, 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 option.


OPTIONS
       By default, pbmreduce does the halftoning after the reduction via bous-
       trophedonic  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.


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


AUTHOR
       Copyright (C) 1988 by Jef Poskanzer.



netpbm documentation		02 August 1989	      Pbmreduce User Manual(0)