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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 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
       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 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 resolution layer has twice the number  of  hori-
       zontal and vertical pixels than the next lower layer.  JBIG files can also store several bits per pixel as sep-
       arate 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, pnmtojbig 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 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 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 resolu-
              tion 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
              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 adap-
              tive 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 implementations.
              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, 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 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 rel-
              evant  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 resolution layer is trans-
              mitted 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 optional algorithms defined in the  JBIG  stan-
              dard.  Just add the numbers of the following options which you want to activate in order to get the num-
              ber 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 normally 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 con-
              formance 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 pnmtojbig creates the BIE, it lists a few technical details 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 for-
       mats 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 package.  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  in directory pub/doc/ISO/JBIG/.

       pnmtojbig is part of the Netpbm package of graphics tools.


SEE ALSO
       pnm(1), 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.



netpbm documentation              20 May 2000         Pnmtojbig User Manual(0)