     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)
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                        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)

                                        - 5 -      Formatted:  September 9, 2008