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Pnmtojbig User Manual(0)			      Pnmtojbig	User Manual(0)

NAME
       pnmtojbig - PNM to JBIG file converter

SYNOPSIS
       pnmtojbig

       [options] [input-file [output-file]]

DESCRIPTION
       This program is part of Netpbm(1).

       pnmtojbig  reads	a PBM or PGM image, compresses it, and outputs the im-
       age 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 particularly 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 single	BIE or
       they can	be stored in several separate BIE files.  All resolution  lay-
       ers  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 resolution layer has twice
       the number of horizontal	and vertical pixels than the next lower	layer.
       JBIG  files  can	 also  store several bits per pixel as separate	bitmap
       planes, and pnmtojbig can read a	PGM  file  and	transform  it  into  a
       multi-bitplane BIE.

OPTIONS
       -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
	      such 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 different BIEs.  Options -l
	      and -h allow you to select the  resolution-layer	interval  that
	      will appear in the created BIE.  The lowest resolution layer has
	      number 0 and this	is also	the default value.  By default,	pnmto-
	      jbig writes all layers.

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

       -b     Use  binary values instead of Gray code words in order to	encode
	      pixel values in multiple bitplanes.  This	option has only	an ef-
	      fect if the input	is a PGM file and if more than one bitplane is
	      produced.	Note that the decoder has to make the  same  selection
	      but  cannot  determine from the BIE, whether Gray	or binary code
	      words were used by the encoder.

       -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 overrides	options	-x and -y, which are usually a
	      more comfortable way of selecting	the number of resolution  lay-
	      ers.

       -s number
	      The JBIG algorithm splits	each image into	a number of horizontal
	      stripes.	This option specifies that each	stripe shall have num-
	      ber lines	in layer 0.  The default value is selected so that ap-
	      proximately 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 neighbour pixels in
	      order to get statistical a priori	knowledge of the  probability,
	      whether the next pixel will be black or white.  One single pixel
	      out of this template of context neighbor	pixels	can  be	 moved
	      around.	Especially for dithered	images it can be a significant
	      advantage	to have	one neighbor 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
	      standard,	 no  higher value than 16 for number is	recommended in
	      order to maintain	interoperability with other  JBIG  implementa-
	      tions.   The  maximal  vertical  offset of the adaptive template
	      pixel is always zero.

       -t number
	      Encode only the specified	number of most significant bit planes.
	      This  option  allows to reduce the depth of an input PGM file if
	      not all bits per pixel are needed	in the output.

       -o number
	      JBIG separates an	image into several horizontal stripes, resolu-
	      tion  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.	 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, layers,
	      planes) is over all layers so that all data of the lowest	 reso-
	      lution layer is transmitted first.

	      The  following  values for number	select these loop arrangements
	      for writing the SDEs (outermost 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  layers  will  be
	      stored  before lower layers.  Default order is 3 which writes at
	      first all	planes of the first stripe and then completes layer  0
	      before continuing	with the next layer and	so on.

       -p number
	      This  option  allows  you	 to activate or	deactivate various op-
	      tional 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      typical prediction (TPBON)

       16     diff. layer typical prediction (TPDON)

       64     layer 0 two-line template	(LRLTWO)

	      Except for special applications (like  communication  with  JBIG
	      subset implementations) and for debugging	purposes you will nor-
	      mally not	want to	change anything	 here.	 The  default  is  28,
	      which provides the best compression result.

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

       -v     After pnmtojbig creates the BIE, it lists	a  few	technical  de-
	      tails of the created file	(verbose mode).

FORMATS
       Most of the format pnmtojbig creates is defined by the JBIG standard.

       The  standard,  however,	 does not specify which	values in the BIE mean
       white and which mean black.  It contains	a recommendation  that	for  a
       single  plane  image  zero mean background and one mean foreground, but
       the Netpbm formats have no concept of foreground	and  background.   And
       the standard says nothing about values for multiple plane BIEs.

       pnmtojbig  follows  Markus Kuhn's implementation	of the standard	in the
       pbmtojbg	program	that comes with	his JBIG library:  If  the  BIE	 is  a
       single  plane  BIE,  zero  means	white and one means black.  If it is a
       multiple	plane BIE, zero	means black and	the maximal value is white.

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

AUTHOR
       pnmtojbig  is  based  on	 the  JBIG library by Markus Kuhn, part	of his
       JBIG-KIT	package.  The pbmtojbg program is part of the  JBIG-KIT	 pack-
       age.   The  most	recent version of that library and tools set is	freely
       available on the	Internet from anonymous	ftp server ftp.informatik.uni-
       erlangen.de   <ftp://ftp.informatik.uni-erlangen.de>	 in  directory
       pub/doc/ISO/JBIG/.

       pnmtojbig is part of the	Netpbm package of graphics tools.

SEE ALSO
       pnm(5), jbigtopnm(1)

LICENSE
       If you use pnmtojbig, you are using various  patents,  particularly  on
       its  arithmetic encoding	method,	and in all probability you do not have
       a license from the patent owners	to do so.

DOCUMENT SOURCE
       This manual page	was generated by the Netpbm tool 'makeman'  from  HTML
       source.	The master documentation is at

	      http://netpbm.sourceforge.net/doc/pnmtojbig.html

netpbm documentation		  20 May 2000	      Pnmtojbig	User Manual(0)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | FORMATS | STANDARDS | AUTHOR | SEE ALSO | LICENSE | DOCUMENT SOURCE

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