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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 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 quan-
              tization 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  gener-
       ates 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.source-
       forge.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)

djvulibre 3.5.27 - Generated Sat Mar 14 16:29:45 CDT 2015
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