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jbgtopbm - JBIG1 to portable bitmap file converter
jbgtopbm
[ options ] [ input-file | - [ output-file ]]
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.
- -
- 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.
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.
This program implements the JBIG1 image coding
algorithm as specified in ISO/IEC 11544:1993 and ITU-T T.82(1993).
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/
>.
pbm(5)
,
pgm(5)
, pbmtojbg(1)
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