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 PBMTOJBG(1)                                                     PBMTOJBG(1)
                                 2003-06-04



 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,
      compresses 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 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 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
                    (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. This is
                    a shortcut for -d 0.

      -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 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



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 PBMTOJBG(1)                                                     PBMTOJBG(1)
                                 2003-06-04



                    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
                    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
                    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
                    template 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 pixels, 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 application profile
                    requires decoders to support horizontal offsets 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



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 PBMTOJBG(1)                                                     PBMTOJBG(1)
                                 2003-06-04



                    input 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 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 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
                    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 to activate or deactivate various
                    optional 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
                    result.



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 PBMTOJBG(1)                                                     PBMTOJBG(1)
                                 2003-06-04



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

      -c            Determine the adaptive template pixel movement 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
                    conformance 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 arithmetic 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
                    completely and the length of the image was known.  The
                    authors 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
                    image 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 final height.

      -f            This option makes the output file comply to the
                    "facsimile 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).





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 PBMTOJBG(1)                                                     PBMTOJBG(1)
                                 2003-06-04



 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
      inserted 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)



































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