PPMDITHER

NAME

      ppmdither - ordered dither for color images

SYNOPSIS

      ppmdither [-dim dimension] [-red shades] [-green shades] [-blue shades]
      [ppmfile]

DESCRIPTION

      Reads a portable pixmap as input, and applies dithering to it to
      reduce the number of colors used down to the specified number of
      shades for each primary.  The default number of shades is red=5,
      green=9, blue=5, for a total of 225 colors.  To convert the image to a
      binary rgb format suitable for color printers, use -red 2 -green 2
      -blue 2.  The maximum number of colors that can be used is 256 and can
      be computed as the product of the number of red, green and blue
      shades.

OPTIONS

      -dim dimension
                    The size of the dithering matrix.  Must be a power of 2.
      -red shades   The number of red shades to be used; minimum of 2.
      -green shades The number of green shades to be used; minimum of 2.
      -blue shades  The number of blue shades to be used; minimum of 2.

DEMONSTRATION

      Let a.ppm be a portable pixmap.
      The following command will dither it:
	ppmmerge ppmdither a.ppm > adither.ppm

BEFORE

AFTER

SEE ALSO

      pnmdepth(1), ppmquant(1), ppm(5)

AUTHOR

      Copyright (C) 1991 by Christos Zoulas.