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).