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pgmnorm(1)									       pgmnorm(1)

       pgmnorm - normalize the contrast in a portable graymap

       pgmnorm [-bpercent N | -bvalue N] [-wpercent N | -wvalue N] [pgmfile]

       Reads a portable graymap as input.  Normalizes the contrast 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.

       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

       All flags can be abbreviated to their shortest unique prefix.

       pgmhist(1), ppmnorm(1), pgm(5)

       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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