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 specified 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  perform 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 performance 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 Léon 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)