cpaldjvu (1)

Leading comments

Copyright (c) 2001-2003 Leon Bottou, Yann Le Cun, Patrick Haffner,
Copyright (c) 2001 AT&T Corp., and Lizardtech, Inc.

This is free documentation; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of
the License, or (at your option) any later version.

The GNU General Public License's references to "object code"
and "executables" are to be interpreted as the output of any
document formatti...

(The comments found at the beginning of the groff file "man1/cpaldjvu.1".)

NAME

cpaldjvu - DjVuDocument encoder for low-color images.

SYNOPSIS

cpaldjvu [options] inputppmfile outputdjvufile

DESCRIPTION

Program cpaldjvu is a DjVuDocument encoder for images containing few colors. It performs best on images containing large solid color areas such as screen dumps. Compression ratios on such images can be much higher than those achieved by or compression.
This program works by first reducing the number of distinct colors to a small specified value using a simple color quantization algorithm. The dominant color is encoded into the background layer. The other colors are encoded into the foreground layer.

OPTIONS

-dpi n

Specify the resolution information encoded into the output file expressed in dots per inch. The resolution information encoded in DjVu files determine how the decoder scales the image on a particular display. Meaningful resolutions range from 25 to 6000. The default value is 300 dpi.

-colors n

Specify a maximum number of distinct colors for the color quantization algorithm. process. The default value is 256. Smaller values can produce much smaller files.

-bgwhite

Cause the background layer to use the lightest quantified color instead of the dominant color.

-verbose

Display informational messages while running.

REMARKS

The color quantization might introduce severe degradation if the image contains photographic areas with a large number of very similar colors. Color quantization problems might be solved by pre-processing the input file with a different quantization program such as ppmquant. Avoid using the error diffusion dithering algorithm. This algorithm generates random dithering patterns that might be very costly to encode.

BUGS

This program should be rewritten as a pre-processor for csepdjvu.

CREDITS

This program was initially written by L'eon Bottou <leonb@users.sourceforge.net> and was improved by Bill Riemers <docbill@sourceforge.net> and many others.

SEE ALSO

djvu(1), pbm(5), ppmquant(1), pnmtogif(1), pnmtopng(1)