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)
