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 particu-
       larly 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  satis-
                     fies 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 resolu-
                     tion 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  multi-
                     ple  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 deter-
                     mine 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, fol-
                     lowed 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)
