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)