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cjb2(1) [debian man page]

CJB2(1) 							   DjVuLibre-3.5							   CJB2(1)

NAME

       cjb2 - Simple DjVuBitonal encoder.

SYNOPSIS

       cjb2  [options] inputfile outputdjvufile

DESCRIPTION

       This  is  a  simple  encoder  for bitonal files.  Argument inputfile is the name of a PBM or bitonal TIFF file containing a single document
       image.  This program produces a DjVuBitonal file named outputdjvufile.

       The default compression process is lossless: decoding the DjVuBitonal file at full resolution will produce an image  exactly  identical	to
       the input file.	Lossy compression is enabled by options -losslevel, -lossy, or -clean.

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  1200.   The
	      default  resolution  for TIFF files is the resolution is the resolution specified by the input file.  The default resolution for PBM
	      files is 300 dpi.

       -lossless
	      Ensure that the encoded image is pixel-per-pixel equal to the initial image.  This option is is equivalent to -losslevel	0  and	is
	      the default.

       -clean Only  remove  flyspecks  from the input image.  This option enables a heuristic algorithm that removes very small marks.	Such marks
	      are often causes by noise and dust during the scanning process.  The threshold mark size is chosen according to the resolution spec-
	      ified with option This option is is equivalent to -losslevel 1.

       -lossy Substitute  patterns  with  small  variations.  In addition to the flyspeck removal heuristic, this option enables an algorithm that
	      encodes certain characters by simply replicating the shape of a previously encoded character with a similar shape.  This	option	is
	      is equivalent to -losslevel 100.

       -losslevel x
	      Specify  the aggressiveness of the lossy compression.  Its argument ranges from 0 to 200.  Higher values generate smaller files with
	      more potential distortions.  Loss level 0 corresponds to lossless encoding.  Loss level 1 performs image cleaning but does not  per-
	      form character substitution at all.  Loss level 100 is intended to provide a good compromise.  Higher loss levels provide marginally
	      better compression at the risk of unacceptable character substitutions.

       -verbose
	      Display informational messages while running.

REMARKS

       Lossless encoding is competitive with that of the Lizardtech commercial encoders.

       Lossy encoding has made much progress thanks to Ilya Mezhirov from the minidjvu project.  This also means that the lossy  encoding  perfor-
       mance  can  change from version to version.  When lossy compression yields inadequate results, simply revert to only using option -clean or
       reduce the parameter of option -losslevel.

       Two features are still missing:

       *  Half-tone detection. Collecting small marks belonging to half-tone patterns would improve compression speed.

       *  Multi-page compression. Matching characters on several pages would improve the compression ratios for multi-page documents.

CREDITS

       This program was initially written by Leon Bottou <leonb@users.sourceforge.net> and was improved by Bill Riemers  <docbill@sourceforge.net>
       and  many  others.   The  pattern matching algorithm for lossy compression was contributed by Ilya Mezhirov <ilya@mezhirov.mccme.ru>.  TIFF
       input routines are inspired by the ones contributed by R. Keith Dennis <dennis@rkd.math.cornell.edu> and Paul Young.

SEE ALSO

       djvu(1), pbm(5).

DjVuLibre-3.5							    10/11/2001								   CJB2(1)

Check Out this Related Man Page

CPALDJVU(1)							   DjVuLibre-3.5						       CPALDJVU(1)

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 val-
	      ues 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 col-
       ors.   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 Leon 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)

DjVuLibre-3.5							    10/11/2001							       CPALDJVU(1)
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