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)