CPALDJVU(1)							   DjVuLibre-3.5						       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 GIF or PNG 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 val-
	      ues 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 col-
       ors.   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 Leon 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)

DjVuLibre-3.5							    10/11/2001							       CPALDJVU(1)