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