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).