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 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 Léon 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)