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 porta-
       ble bitmap (PBM) file.

       JBIG1  is  a highly effective lossless compression algo-
       rithm 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 resolu-
       tions in one or  several  BIEs.  All  resolution  layers
       except  the lowest one are stored efficiently as differ-
       ences 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 avail-
                     able.

       -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 avail-
                     able. 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  pro-
                     duced.   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)
