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)