Version 1.0 of the JBIG-KIT lossless image compression library available ------------------------------------------------------------------------ Markus Kuhn -- 1998-04-11 The latest release of JBIG-KIT can be downloaded over the Internet with anonymous ftp from and from a number of other servers. JBIG-KIT implements a highly effective data compression algorithm for bi-level high-resolution images such as fax pages or scanned documents. JBIG-KIT provides a portable library of compression and decompression functions with a documented interface that you can very easily include 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 Jef Poskanzer's PBM graphics file conversion package). 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 "JBIG standard". JBIG (Joint Bi-level Image experts Group) is the committee which developed this international standard for the lossless compression of images using arithmetic coding. Like the well-known compression algorithms JPEG and MPEG, also JBIG has been developed and published by the International Organization for Standardization (ISO) and the International Telecommunication Union (ITU) (see also and ). See also . The JBIG compression algorithm offers the following features: - Close to state-of-the-art lossless compression ratio for high resolution bi-level images. - Around 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 JBIG. - Up to 30 times better compression of scanned images with dithered images compared to G4 fax compression. - Around 2 times better compression on typical 300 dpi documents compared to 'gzip -9' on raw bitmaps. - Around 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. - JBIG supports hierarchical "progressive" encoding, that means it is possible to encode a low resolution image first, followed by resolution enhancement data. 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 JBIG image in progressive encoding mode together require not much more space than a normal non-progressive mode encoded image (which JBIG also supports). - The progressive encoding mode utilizes a very sophisticated resolution reduction algorithm which offers highest quality low resolution versions that preserve the shape of characters as well as the integrity of thin lines and dithered images. - JBIG supports multiple bit planes and can this way also be used for greyscale and color images, although the main field of application is compression of bi-level images, i.e. images with only two different pixel values. For greyscale images with up to 6 bit per pixel, JBIG performs superior to JPEG's lossless mode. JBIG-KIT is free software under the GNU General Public License. For other license arrangements contact the author. JBIG-KIT provides a portable library implemented in ANSI/ISO C for encoding and decoding JBIG data streams together with documentation. The library is not intended for 8-bit or 16-bit machine architectures (e.g., old MS-DOS C compilers) on which a number of very efficient optimization techniques used in this software are not possible. For maximum performance, a 32-bit processor is required (64-bit systems work too, of course). On architectures with 16-bit pointer arithmetic, only very small images can be processed. Special features of the JBIG-KIT implementation are: - Fully reentrant multithread-capable design (no global or static variables, isolated malloc()/free() calls, etc.). - Capable of handling incomplete and growing JBIG 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 JBIG 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). - 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 greyscale images. - Ready-to-use pbmtojbg and jbgtopbm converters. Changes in version 1.0 (1998-04-11): - two bugs fixed that caused the encoder and decoder to fail under certain modes of operation with several bit planes - added new functions jbg_split_planes(), jbg_dec_merge_planes(), and jbg_dec_getsize_merged() for easy handling of greyscale images - added support for compressing greyscale PGM files to pbmtojbg and jbgtopbm - more changes to avoid paranoid compiler warnings Changes in version 0.9 (1996-01-09): - encoder won't break any more on input bitmap data with incorrect zero padding - pbmtojbg displays a warning if input file has incorrect zero padding - various minor improvements suggested by Stefan Willer - many minor changes in order to avoid warnings from paranoid compilers Changes in version 0.8 (1995-09-20): - namespace cleared up, all names externally visible from the library start now with jbg_ or JBG_ - minor non-critical bug fixed which caused library to fail compatibility test and showed up especially on DEC Alpha systems - jbg_dec_gethight() is now called jbg_dec_getheight() - filenames conform now to MS-DOS limits - Bug in pbmtojbg fixed (handling of ASCII PBM files) Changes in version 0.7 (1995-06-10): - more problems on 16-bit int systems and on Macintosh systems fixed (special thanks to Jean-Pierre Gachen ) - global Makefile Changes in version 0.6 (1995-06-08): - memory leak fixed - should now also work on systems where int is only 16-bit large - changes of the JBIG "Technical Corrigendum 1" included (special thanks to Dr. Sebestyen from Siemens AG for sending me a copy of the draft) First release: version 0.5 (1995-05-28) Please send all questions, problem reports, patches, suggestions, success stories, comments, etc. to mkuhn at acm.org I will try to provide free support and maintenance for this software at least for the next few months depending on my available time. This library has been published in the hope that it will encourage the development of good freely available scanned document handling and transmission systems for the Internet so that large amounts of scanned text can be made available to the global village easily. Happy compressing ... Markus Kuhn -- Markus G. Kuhn, Security Group, Computer Lab, Cambridge University, UK email: mkuhn at acm.org, home page: