JBGTOPBM(1)                                                        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  multi-
       ple  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  reso-
                     lution 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  reso-
                     lution 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 bit-
                     plane 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)