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)