cpaldjvu - DjVuDocument encoder for low-color images.
cpaldjvu [options] inputppmfile
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.
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.
This program should be rewritten as a pre-processor for csepdjvu.
This program was initially written by Léon Bottou
<firstname.lastname@example.org> and was improved by Bill Riemers
<email@example.com> and many others.
djvu(1), pbm(5), ppmquant(1), pnmtogif(1),
- -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
- -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.