JBGTOPBM(1) JBGTOPBM(1)
2003-06-04
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
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JBGTOPBM(1) JBGTOPBM(1)
2003-06-04
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)
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