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JBGTOPBM(1)            DragonFly General Commands Manual           JBGTOPBM(1)


NAME

       jbgtopbm - JBIG1 to portable bitmap file converter


SYNOPSIS

       jbgtopbm [ options ] [ input-file | -  [ output-file ]]


DESCRIPTION

       Reads in a JBIG1 bi-level image entity (BIE) from a file or standard
       input, decompresses it, and outputs a portable bitmap (PBM) 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 in one or
       several BIEs. All resolution layers except the lowest one are stored
       efficiently as differences to the next lower resolution layer. Options
       -x and -y can be used to stop the decompression at a specified maximal
       output image size. With option -m the input file can consist of
       multiple concatenated BIEs which contain different increasing
       resolution layers of the same image.

       If more than one bit per pixel is stored in the JBIG1 file, then a PGM
       file will be produced.


OPTIONS

       -             A single hyphen instead of an input file name will cause
                     jbgtopbm to read the data from standard input instead
                     from a file.

       -x number     Decode only up to the largest resolution layer which is
                     still not more than number pixels wide. If no such
                     resolution layer exists, then use the smallest one
                     available.

       -y number     Decode only up to the largest resolution layer which is
                     still not more than number pixels high. If no such
                     resolution layer exists, then use the smallest one
                     available. Options -x and -y can also be used together in
                     which case the largest layer that satisfies both limits
                     will be selected.

       -m            Process multiple concatenated BIEs. If there are bytes
                     left after the final SDE in the first BIE, then with this
                     option jbgtopbm will attempt to decode these as the start
                     of another BIE that may contain higher resolution data.
                     Normally, any remaining bytes will generate a warning
                     message.

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

       -d            Diagnose a single BIE. With this option, jbgtopbm will
                     print a summary of the header information found in the
                     input file, followed by a list of all PSCD and ESC marker
                     sequences encountered until the end of the file is
                     reached.

       -p number     If the input contains multiple bitplanes, then extract
                     only the specified single plane as a PBM file. The first
                     plane has number 0.


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 jbgtopbm 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), pbmtojbg(1)

                                  2003-06-04                       JBGTOPBM(1)

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