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CJB2(1)				 DjVuLibre-3.5			       CJB2(1)

       cjb2 - Simple DjVuBitonal encoder.

       cjb2  [options] inputfile outputdjvufile

       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.

       -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 res-
	      olution for PBM files is 300 dpi.

	      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

       -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 argu-
	      ment 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 unaccept-
	      able character substitutions.

	      Display informational messages while running.

       Lossless	encoding is competitive	with that of the Lizardtech commercial

       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 in-
       adequate	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.

       This  program was initially written by Leon Bottou <leonb@users.source-> and was improved by Bill  Riemers  <>
       and  many others.  The pattern matching algorithm for lossy compression
       was contributed by Ilya Mezhirov	<>.  TIFF	 input
       routines	 are inspired by the ones contributed by R. Keith Dennis <den-> and Paul Young.

       djvu(1),	pbm(5).

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


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