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PBMTOJBG(1)					      PBMTOJBG(1)

NAME
       pbmtojbg - portable bitmap to JBIG file converter

SYNOPSIS
       pbmtojbg [ options ] [ input-file | -  [ output-file ]]

DESCRIPTION
       Reads  in  a portable bitmap (PBM) from a file or standard
       input, compresses it and outputs the image as a	JBIG  bi-
       level image entity (BIE) file.

       JBIG  is a highly effective lossless compression algorithm
       for bi-level images (one bit per pixel) which is	 particu-
       larly suitable for scanned document pages.

       A  JBIG encoded image can be stored in several resolutions
       (progressive mode).  These resolution layers can be stored
       all in one singe BIE or they can be stored in several sep-
       arate BIE files.	 All resolution layers except the  lowest
       one  are	 stored	 merely	 as differences to the next lower
       resolution layer, because this requires	less  space  than
       encoding	 the full image completely every time. Each reso-
       lution layer has twice the number of horizontal and verti-
       cal pixels than the next lower layer.  JBIG files can also
       store several bits per pixel as	separate  bitmap  planes,
       however this program stores only one single plane.

OPTIONS
       -	     A	single	hyphen	instead	 of an input file
		     name will cause pbmtojbg to  read	the  data
		     from standard input instead from a file.

       -q	     Encode  the  image	 in one single resolution
		     layer (sequential mode). This is usually the
		     most   efficient	compression   method.  By
		     default, the number of resolution layers  is
		     chosen  automatically  so	that  the  lowest
		     layer image is not larger	than  640  x  480
		     pixels.

       -x number     Specify  the  maximal horizontal size of the
		     lowest resolution layer.  The default is 640
		     pixels.

       -y number     Specify  the  maximal  vertical  size of the
		     lowest resolution layer.  The default is 480
		     pixels.

       -l number     Select the lowest resolution layer that will
		     be written to the BIE.  It	 is  possible  to
		     store  the	 various  resolution  layers of a
		     JBIG image in progressive mode into  differ-
		     ent  BIEs. Options -l and -h allow to select

			    1996-01-09				1

PBMTOJBG(1)					      PBMTOJBG(1)

		     the resolution  layer  intervall  that  will
		     appear  in the created BIE. The lowest reso-
		     lution layer has number 0 and this	 is  also
		     the  default  value.  By  default all layers
		     will be written.

       -h number     Select the	 highest  resolution  layer  that
		     will  be  written to the BIE. By default all
		     layers will be written. See also option  -l.

       -d number     Specify  the  total  number  of differential
		     resolution layers into which the input image
		     will  be  split  in  addition  to the lowest
		     layer. Each  additional  layer  reduces  the
		     size  of  layer 0 by 50 %. This option over-
		     rides options -x and -y which are usually	a
		     more comfortable way of selecting the number
		     of resolution layers.

       -s number     The JBIG algorithm splits each image into	a
		     number  of	 horizontal  stripes. This option
		     specifies that each stripe shall have number
		     lines  in	layer  0.  The	default	 value is
		     selected so that  approximately  35  stripes
		     will be used for the whole image.

       -m number     Select  the maximum horizontal offset of the
		     adaptive template pixel.  The  JBIG  encoder
		     uses a number of neigbour pixels in order to
		     get statistical a priori  knowledge  of  the
		     propability,  whether the next pixel will be
		     black or white. One single pixel out of this
		     template  of context neighbour pixels can be
		     moved around. Especially for dithered images
		     it	 can  be  a significant advantage to have
		     one neighbour pixel  which	 has  a	 distance
		     large enough to cover the period of a dither
		     function. By default, the adaptive	 template
		     pixel can be moved up to 8 pixels away. This
		     encoder supports up to 23 pixels, however as
		     decoders  are  only  required  to support at
		     least a distance of 16 pixels by  the  stan-
		     dard,  no higher value than 16 for number is
		     recommended in order to maintain  interoper-
		     ability with other JBIG implementations. The
		     maximal vertical offset of the adaptive tem-
		     plate pixel is always zero.

       -o number     JBIG  separates  an image into several hori-
		     zontal  stripes,	resolution   layers   and
		     planes, were each plane contains one bit per
		     pixel. One single stripe in  one  plane  and
		     layer  is	encoded	 as  a	data  unit called
		     stripe data entity	 (SDE)	inside	the  BIE.

			    1996-01-09				2

PBMTOJBG(1)					      PBMTOJBG(1)

		     There  are	 12  different possible orders in
		     which the SDEs can be stored inside the  BIE
		     and  number selects which one shall be used.
		     The order of the SDEs is only  relevant  for
		     applications that want to decode a JBIG file
		     which has not yet	completely  arrived  from
		     e.g.   a	slow   network	connection.   For
		     instance some applications prefer	that  the
		     outermost	of the three loops (stripes, lay-
		     ers, planes) is over all layers so that  all
		     data  of  the  lowest  resolution	layer  is
		     transmitted first.
		     The following values for number select these
		     loop arrangements for writing the SDEs (out-
		     ermost loop first):

			0      planes, layers, stripes
			2      layers, planes, stripes
			3      layers, stripes, planes
			4      stripes, planes, layers
			5      planes, stripes, layers
			6      stripes, layers, planes

		     All loops count starting with zero,  however
		     by	 adding	 8  to	the above order code, the
		     layer loop can be reversed so that it counts
		     down to zero and then higher resolution lay-
		     ers will  be  stored  before  lower  layers.
		     Default order is 3 which writes at first all
		     planes of the first  stripe  and  then  com-
		     pletes  layer  0  before continuing with the
		     next layer and so on.

       -p number     This option allows to activate or deactivate
		     various  optional	algorithms defined in the
		     JBIG standard. Just add the numbers  of  the
		     following options which you want to activate
		     in order to get the number value:

			4      deterministic prediction (DPON)
			8      layer 0 typical prediction (TPBON)
		       16      diff. layer typ. pred. (TPDON)
		       64      layer 0 two-line template (LRLTWO)

		     Except for special applications (like commu-
		     nication  with  JBIG subset implementations)
		     and for debugging purposes you will normally
		     not   want	 to  change  anything  here.  The
		     default is 28, which provides the best  com-
		     pression result.

       -c	     The  adaptive  template  pixel  movement  is
		     determined as suggested in annex  C  of  the
		     standard.	By  default  the  template change

			    1996-01-09				3

PBMTOJBG(1)					      PBMTOJBG(1)

		     takes place directly in the next line  which
		     is most effective. However a few conformance
		     test examples in the  standard  require  the
		     adaptive template change to be delayed until
		     the first line  of	 the  next  stripe.  This
		     option  selects this special behavior, which
		     is normally not required except in order  to
		     pass some conformance test suite.

       -v	     After  the BIE has been created, a few tech-
		     nical details of the created  file	 will  be
		     listed (verbose mode).

STANDARDS
       This program implements the JBIG image coding algorithm as
       specified in ISO/IEC 11544:1993 and ITU-T T.82(1993).

AUTHOR
       The pbmtojbg program is	part  of  the  JBIG-KIT	 package,
       which  has beed developed by Markus Kuhn.  The most recent
       version of this portable JBIG library  and  tools  set  is
       freely available on the Internet from anonymous ftp server
       ftp.informatik.uni-erlangen.de	     in		directory
       pub/doc/ISO/JBIG/.   Bug	  reports   should   be	 sent  to
       <mskuhn@cip.informatik.uni-erlangen.de>.

SEE ALSO
       pbm(5), jbgtopbm(1)

			    1996-01-09				4

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