JBIG-KIT

by Markus Kuhn

JBIG-KIT implements a highly effective data compression algorithm for bi-level high-resolution images such as fax pages or scanned documents.

Download

The latest release of JBIG-KIT is

  http://www.cl.cam.ac.uk/~mgk25/download/jbigkit-2.0.tar.gz (2008-08-30)

See the revision history for a summary of recent changes. Please subscribe to JBIG-KIT’s freshmeat.net entry if you are interested in receiving automatic notifications of new releases.

Description

JBIG-KIT provides a portable library of compression and decompression functions with a documented interface that you can include very easily into your image or document processing software. In addition, JBIG-KIT provides ready-to-use compression and decompression programs with a simple command line interface (similar to the converters found in netpbm).

JBIG-KIT implements the specification

International Standard ISO/IEC 11544:1993 and ITU-T Recommendation T.82(1993):
Information technology — Coded representation of picture and audio information — Progressive bi-level image compression

which is commonly referred to as the “JBIG1 standard”. JBIG (Joint Bi-level Image experts Group) is the committee that developed this international standard for the lossless compression of images through arithmetic coding. Like the well-known JPEG and MPEG compression standards, JBIG has been developed and published through the International Organization for Standardization (ISO) and the International Telecommunication Union (ITU).

The JBIG1 compression algorithm offers the following features:

• Close to state-of-the-art lossless compression ratio for high resolution bi-level images.
• About 1.1 to 1.5 times better compression ratio on typical scanned documents compared to G4 fax compression (ITU-T T.6), which has been the best compression algorithm for scanned documents available prior to JBIG1.
• Up to 30 times better compression of scanned images with dithered images compared to G4 fax compression.
• About 2 times better compression on typical 300 dpi documents compared to “gzip -9” on raw bitmaps.
• About 3–4 times better compression than GIF on typical 300 dpi documents.
• Even much better competitive compression results on computer generated images, which are free of scanning distortions.
• JBIG1 supports hierarchical “progressive” encoding, meaning that it is possible to encode a low resolution image first, followed by resolution enhancement data, without adding a lot of redundancy. This allows, for instance, a document browser to display already a good 75 dpi low resolution version of an image, while the data necessary to reconstruct the full 300 dpi version for laser printer reproduction is still arriving (say over a slow network link or mass storage medium).
• The various resolution layers of a JBIG1 image in progressive encoding mode combined require not much more space than a normal non-progressive mode encoded image (which JBIG1 also supports).
• The progressive mode utilizes a sophisticated resolution-reduction algorithm to generate high-quality low resolution versions that preserve the shape of characters as well as the integrity of thin lines and dithered images.
• JBIG1 supports multiple bit planes. Therefore, it can also be used for grayscale and color images. While its main field of application are bi-level images, that is images with only two different pixel values (black and white), JBIG1 has also been reported to perform better than JPEG’s original lossless mode on grayscale images that have up to 6 bits per pixel.

JBIG-KIT is free software under the GNU General Public License (for commercial licenses, see below). JBIG-KIT provides a portable library implemented in ANSI/ISO C for encoding and decoding JBIG1 data streams together with documentation.

Special features of the JBIG-KIT implementation are:

• Fully reentrant multithread-capable design, also suitable for use in embedded systems (no global or static variables, isolated malloc()/free() calls, etc.).
• Capable of handling incomplete and growing JBIG1 data streams in order to allow earliest display of low resolution versions.
• Capable of handling several incoming data streams simultaneously in one single process and task.
• Especially designed with applications in mind that want to display incoming data as early as possible (e.g., similar to the way in which Netscape Navigator handles incoming GIF images).
• Implements all JBIG1 features and options, including progressive and sequential encoding, multiple bit planes, user specified resolution reduction and deterministic prediction tables, adaptive template changes for optimal performance on half-tone images, deterministic prediction, typical prediction in lowest and differential layers, various stripe orderings, etc. Only the SEQ and HITOLO options are currently not supported by the decoder (they are normally never required, but could be added later in case of user requirements).
• Suitable for fax applications, satisfies ITU-T T.85 profile starting from version 1.5
• Efficient code, optimized utilization of 32-bit processor registers.
• Very easy to use documented C library interface.
• Included Gray code conversion routines for efficient encoding of grayscale images.
• Ready-to-use pbmtojbg and jbgtopbm converters.

Limitations: The library was not designed for machine architectures with registers smaller than 32 bits (e.g., old MS-DOS C compilers, 8/16-bit microcontrollers or DSPs) on which a number of very efficient optimization techniques used in this software are not effective. For maximum performance, a 32-bit processor is required (64-bit systems work fine, too). On architectures with 16-bit pointer arithmetic, only very small images can be processed.

Applications: Examples of standard data transfer formats that encapsulate JBIG1 streams include Zenographics Zj-stream, TIFF-FX (RFC 2301), and fax.

Licensing

Public licence: You can use JBIG-KIT free of charge under the conditions of the GNU General Public Licence. Linking JBIG-KIT statically or dynamically with other modules is making a combined work based on JBIG-KIT. Thus, the terms and conditions of the GNU General Public License cover the whole combination.

Commercial licence: Alternatively, you can also get a commercial licence for JBIG-KIT for applications that are incompatible with GPL requirements. This software licence will still require you to obtain any necessary patent licences yourself. For details, please contact Robert Fender or Margaret Wilkinson at Cambridge Enterprise (enquiries@enterprise.cam.ac.uk).

Patents: Annex E of the JBIG1 standard lists a number of patents that might be applicable to implementations until 2010. JBIG-KIT comes without any patent licence. More details ...

Support

Feel free to email me questions, problem reports, patches, suggestions, success stories, comments, etc. I will try to provide free support and maintenance for this software for the foreseeable future depending on my available time.

From time to time, I may also be available to do small consulting projects in relation to JBIG1.

Related links:

• Lee Howard released a patch to add JBIG-KIT support to libtiff-3.7.2.
• The jbig2dec project is working on an open source implementation of a decoder for the JBIG2 standard (ISO 14492/ITU-T T.88), which offers lossy bi-level compression factors up to 100.
• Szalai Robert’s pbmtozjs allows to use HP LaserJet 1000 printer from Linux.

created 1995-06-08 – last modified 2008-08-30 – http://www.cl.cam.ac.uk/~mgk25/jbigkit/