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PBMTOJBG(1)		    General Commands Manual		   PBMTOJBG(1)

NAME
       pbmtojbg	- portable bitmap to JBIG1 file	converter

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

DESCRIPTION
       Reads  in  a  portable bitmap (PBM) from	a file or standard input, com-
       presses it, and outputs the image as  a	JBIG1  bi-level	 image	entity
       (BIE) file.

       JBIG1 is	a highly effective lossless compression	algorithm for bi-level
       images (one bit per pixel), which is particularly suitable for  scanned
       document	pages.

       A JBIG1 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.
       JBIG1 files can also store several bits per pixel  as  separate	bitmap
       planes, and pbmtojbg can	read a PGM file	and transform it into a	multi-
       bitplane	BIE.

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  (sequen-
		     tial  mode).  This	is usually the most efficient compres-
		     sion 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. This is  a  shortcut
		     for -d 0.

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

       -y number     Specify the maximal vertical size of the  lowest  resolu-
		     tion 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  resolu-
		     tion  layers  of  a  JBIG1	image in progressive mode into
		     different BIEs. Options -l	and -h	allow  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 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.

       -b	     Use binary	values instead of Gray code words in order  to
		     encode  pixel  values  in multiple	bitplanes. This	option
		     has only an effect	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  lay-
		     ers  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  se-
		     lecting the number	of resolution layers.

       -s number     The  JBIG1	 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 tem-
		     plate pixel.  The JBIG1 encoder uses ten neighbour	pixels
		     to	estimate the probability of the	next pixel being black
		     or	white. It can move one out of these ten	 pixels.  This
		     is	 especially useful for dithered	images,	as long	as the
		     distance of this adaptive pixel can be  adjusted  to  the
		     period  of	 the  dither pattern. By default, the adaptive
		     template pixel is allowed to move up  to  8  pixels  away
		     horizontally.  This  encoder supports distances up	to 127
		     pixels. Annex A of	the standard  suggests	that  decoders
		     should  support at	least a	horizontal distance of 16 pix-
		     els, so using values not higher than 16 for number	 might
		     increase the chances of interoperability with other JBIG1
		     implementations. On the other hand, the T.85 fax applica-
		     tion profile requires decoders to support horizontal off-
		     sets up to	127 pixels, which the maximum value  permitted
		     by	 the  standard.	 (The  maximal	vertical offset	of the
		     adaptive template pixel is	always zero for	this encoder.)

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

       -o number     JBIG1 separates an	image into several horizontal 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. There are 12	different possible or-
		     ders 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  de-
		     code  a  JBIG1  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	resolution layer is transmitted	first.
		     The  following  values  for  number select	these loop ar-
		     rangements	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	to activate or deactivate various  op-
		     tional algorithms defined in the JBIG1 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 communication with
		     JBIG1 subset implementations) and for debugging  purposes
		     you  will	normally not want to change anything here. The
		     default is	28, which provides the	best  compression  re-
		     sult.

       -C string     Add  the  string  in a comment marker segment to the pro-
		     duced data	stream.	(There is no support  at  present  for
		     adding comments that contain the zero byte.)

       -c	     Determine	the  adaptive  template	pixel movement as sug-
		     gested in annex C of the standard.	By  default  the  tem-
		     plate change takes	place directly in the next line, which
		     is	most effective.	However, a few conformance test	 exam-
		     ples 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 nor-
		     mally not required	except in order	to pass	 some  confor-
		     mance tests.

       -r	     Use the SDRST marker instead of the normal	SDNORM marker.
		     The probably only useful application of this option is to
		     generate  test  data for checking whether a JBIG1 decoder
		     has implemented SDRST correctly. In a normal  JBIG1  data
		     stream, each stripe data entity (SDE) is terminated by an
		     SDNORM marker, which preserves the	state  of  the	arith-
		     metic  encoder (and more) for the next stripe in the same
		     layer. The	alternative SDRST marker resets	this state  at
		     the end of	the stripe.

       -Y number     A	long  time  ago, there were fax	machines that couldn't
		     even hold a single	page in	 memory.  They	had  to	 start
		     transmitting  data	 before	 the  page was scanned in com-
		     pletely and the length of the image was known.   The  au-
		     thors  of	the  standard  added a rather ugly hack	to the
		     otherwise beautiful JBIG1 format  to  support  this.  The
		     NEWLEN  marker  segment  can  override  the  image	height
		     stated in the BIE	header	anywhere  later	 in  the  data
		     stream.  Normally	pbmtojbg never generates NEWLEN	marker
		     segments, as it knows the correct image  height  when  it
		     outputs  the  header.  This option	is solely intended for
		     the purpose of generating test files with	NEWLEN	marker
		     segments.	It can be used to specify a higher initial im-
		     age height	for use	in the BIE header, and	pbmtojbg  will
		     then  add	a NEWLEN marker	segment	at the latest possible
		     opportunity to the	data stream to signal the correct  fi-
		     nal height.

       -f	     This  option makes	the output file	comply to the "facsim-
		     ile application profile" defined in ITU-T	Recommendation
		     T.85.  It	is  a shortcut for -q -o 0 -p 8	-s 128 -t 1 -m
		     127.

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

BUGS
       Using  standard input and standard output for binary data works only on
       systems where there is no difference between binary  and	 text  streams
       (e.g.,  Unix). On other systems (e.g., MS-DOS), using standard input or
       standard	output may cause control characters like CR or LF  to  be  in-
       serted or deleted and this will damage the binary data.

STANDARDS
       This  program  implements the JBIG1 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  been
       developed  by  Markus  Kuhn.   The most recent version of this portable
       JBIG1	library	   and	   tools     set     is	    available	  from
       <http://www.cl.cam.ac.uk/~mgk25/jbigkit/>.

SEE ALSO
       pbm(5), pgm(5), jbgtopbm(1)

				  2003-06-04			   PBMTOJBG(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | BUGS | STANDARDS | AUTHOR | SEE ALSO

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