cpaldjvu(1)

1CPALDJVU(1)                      DjVuLibre-3.5                     CPALDJVU(1)
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NAME

6       cpaldjvu - DjVuDocument encoder for low-color images.
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SYNOPSIS

10       cpaldjvu  [options] inputppmfile outputdjvufile
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DESCRIPTION

14       Program  cpaldjvu  is  a DjVuDocument encoder for images containing few
15       colors.  It performs best on images containing large solid color  areas
16       such  as  screen  dumps.  Compression ratios on such images can be much
17       higher than those achieved by GIF or PNG compression.
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19       This program works by first reducing the number of distinct colors to a
20       small specified value using a simple color quantization algorithm.  The
21       dominant color is encoded into the background layer.  The other  colors
22       are encoded into the foreground layer.
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OPTIONS

26       -dpi n Specify  the resolution information encoded into the output file
27              expressed in dots per inch. The resolution  information  encoded
28              in  DjVu  files  determine how the decoder scales the image on a
29              particular display.  Meaningful resolutions  range  from  25  to
30              6000.  The default value is 300 dpi.
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32       -colors n
33              Specify  a maximum number of distinct colors for the color quan‐
34              tization algorithm.  process. The default value is 256.  Smaller
35              values can produce much smaller files.
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37       -bgwhite
38              Cause  the background layer to use the lightest quantified color
39              instead of the dominant color.
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41       -verbose
42              Display informational messages while running.
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REMARKS

46       The color quantization might introduce severe degradation if the  image
47       contains photographic areas with a large number of very similar colors.
48       Color quantization problems might be solved by pre-processing the input
49       file  with  a  different  quantization program such as ppmquant.  Avoid
50       using the error diffusion dithering algorithm.  This  algorithm  gener‐
51       ates random dithering patterns that might be very costly to encode.
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BUGS

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

59       This  program was initially written by Léon Bottou <leonb@users.source‐
60       forge.net> and was improved by Bill  Riemers  <docbill@sourceforge.net>
61       and many others.
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