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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 spec-
       ified 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 pro-
       duced.

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  small-
		     est 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  small-
		     est 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)
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