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       cpaldjvu - DjVuDocument encoder for low-color images.


       cpaldjvu  [options] inputppmfile outputdjvufile


       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.


       -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.

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

              Display informational messages while running.


       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


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


       This    program    was    initially    written    by    Leon     Bottou
       <>   and   was   improved  by  Bill  Riemers
       <> and many others.


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