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       ppmdist - simplistic grayscale assignment for machine generated, color images


       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 repetitions).


       -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
                     distributed 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)