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ppmquant(1) PBM Plus ppmquant(1)
NAME
ppmquant - quantize the colors in a portable pixmap down to
a specified number
SYNOPSIS
ppmquant [-floyd|-fs] <ncolors> [ppmfile]
DESCRIPTION
Reads a portable pixmap as input. Chooses <ncolors> colors
to best represent the image, maps the existing colors to the
new ones, and writes a portable pixmap as output.
The quantization method is Heckbert's "median cut".
The -floyd flag adds a Floyd-Steinberg error diffusion step.
This may give better results on images where the unmodified
quantization has banding or other artifacts. It takes maybe
20% more CPU time.
All flags can be abbreviated to their shortest unique pre-
fix.
REFERENCES
"Color Image Quantization for Frame Buffer Display" by Paul
Heckbert, SIGGRAPH '82 Proceedings, page 297.
SEE ALSO
ppmcscale(1), ppm(5)
AUTHOR
Copyright (C) 1989 by Jef Poskanzer.
Permission to use, copy, modify, and distribute this
software and its documentation for any purpose and without
fee is hereby granted, provided that the above copyright
notice appear in all copies and that both that copyright
notice and this permission notice appear in supporting docu-
mentation. This software is provided "as is" without
express or implied warranty.
Printed 5/25/90 18 May 1989 1