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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 con-
       taining 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 resolu-
              tion information encoded in DjVu files determine how the decoder scales the image on a  particular  dis-
              play.  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  Leon  Bottou <leonbATusers.net> and was improved by Bill
       Riemers <docbillATsourceforge.net> and many others.


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



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