pgmnorm

 

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 pgmnorm(1)                                             pgmnorm(1)
 
 
 
NAME
        pgmnorm - normalize the contrast in a portable graymap
 
SYNOPSIS
        pgmnorm  [-bpercent  N | -bvalue N] [-wpercent N | -wvalue
        N] [pgmfile]
 
DESCRIPTION
        Reads a portable graymap as input.   Normalizes  the  con­
        trast by forcing the lightest pixels to white, the darkest
        pixels to  black,  and  linearly  rescaling  the  ones  in
        between; and produces a portable graymap as output.
 
OPTIONS
        By default, the darkest 2 percent of all pixels are mapped
        to black, and the lightest 1 percent are mapped to  white.
        You  can override these percentages by using the -bpercent
        and -wpercent flags, or you can specify  the  exact  pixel
        values  to  be  mapped  by  using  the -bvalue and -wvalue
        flags.  Appropriate numbers for the flags  can  be  gotten
        from  the  pgmhist  tool.  If you just want to enhance the
        contrast, then choose values at elbows in  the  histogram;
        e.g.  if  value 29 represents 3% of the image but value 30
        represents 20%, choose 30 for  bvalue.   If  you  want  to
        lighten  the  image,  then set bvalue to 0 and just fiddle
        with wvalue; similarly, to darken the image, set wvalue to
        maxval and play with bvalue.
 
        All flags can be abbreviated to their shortest unique pre­
        fix.
 
SEE ALSO
        pgmhist(1), ppmnorm(1), pgm(5)
 
AUTHOR
        Partially based on the fbnorm filter in Michael  Mauldin's
        "Fuzzy Pixmap" package.
 
        Copyright (C) 1989 by Jef Poskanzer.
 
 
 
                          28 February 1989              pgmnorm(1)

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