ppmdist [-intensity|-frequency] [ppmfile]

       Reads a portable pixmap  as  input,  performs  a  simplistic  grayscale
       assignment intended for use with grayscale or bitmap printers.

       Often  conversion from ppm to pgm will yield an image with contrast too
       low for good printer output.  The program  maximizes  contrast  between
       the gray levels output.

       A ppm input of n colors is read, and a pgm of n gray levels is written.
       The gray levels take on the values 0..n-1, while maxval takes on n-1.

       The mapping from color to stepped grayscale can be performed  in  order
       of  input  pixel intensity, or input pixel frequency (number of repeti-

       -frequency    Sort input colors by the number of times a color  appears
                     in  the  input,  before  mapping  to  evenly  distributed
                     graylevels of output.  -intensity Sort  input  colors  by
                     their  grayscale intensity, before mapping to evenly dis-
                     tributed graylevels of output.  This is the default.

       Helpful only for images with a very small number  of  colors.   Perhaps
       should have been an option to ppmtopgm(1).

       ppmtopgm(1), ppmhist(1), ppm(5)

       Copyright (C) 1993 by Dan Stromberg.

                                 22 July 1992                       ppmdist(1)
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