Table of Contents
jbgtopbm - JBIG to portable bitmap file converter
jbgtopbm [
options ] [ input-file | - [ output-file ]]
Reads in a JBIG bi-level image entity (BIE) from a file or standard
input, decompresses it, and outputs a portable bitmap (PBM) file.
JBIG
is a highly effective lossless compression algorithm for bi-level images
(one bit per pixel), which is particularly suitable for scanned document
pages.
A JBIG 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. The input file can consist of several concatenated BIEs which
contain different increasing resolution layers of the same image.
If more
than one bit per pixel is stored in the JBIG 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.
- -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 BIE. With this option, jbgtopbm will only
print a summary of the header information found in the input file and then
exit.
- -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 JBIG 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
JBIG library and tools set is freely available on the Internet from anonymous
ftp server ftp.informatik.uni-erlangen.de in directory pub/doc/ISO/JBIG/. Bug
reports should be sent to <mkuhn@acm.org>.
pbm(5)
, pgm(5)
, pbmtojbg(1)
Table of Contents