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diff --git a/converter/other/jbig/libjbig/ANNOUNCE b/converter/other/jbig/libjbig/ANNOUNCE new file mode 100644 index 00000000..15ce550d --- /dev/null +++ b/converter/other/jbig/libjbig/ANNOUNCE @@ -0,0 +1,172 @@ + +JBIG-KIT lossless image compression library +------------------------------------------- + +by Markus Kuhn + + +The latest release of JBIG-KIT can be downloaded from + + http://www.cl.cam.ac.uk/~mgk25/jbigkit/ + +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 two variants of a portable library of compression +and decompression functions with a documented interface. 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", + <http://www.itu.int/rec/T-REC-T.82>, + +which is commonly referred to as the "JBIG1 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, JBIG has also been developed and published by the International +Organization for Standardization (ISO) and the International +Telecommunication Union (ITU). See also + + http://www.jpeg.org/jbig/ + http://www.iso.ch/ + http://www.itu.int/ + +The JBIG 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 JBIG. + + - 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. + + - 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 quite sophisticated + resolution reduction algorithm which offers high 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 grayscale 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 grayscale images with up to + 6 bit per pixel, JBIG performs superior to JPEG's lossless + mode. + +JBIG-KIT can be used as free software under the GNU General Public +License. Other license arrangements more suitable for commercial +applications are available as well, please contact the author for +details. JBIG-KIT provides two portable libraries implemented in +ANSI/ISO C for encoding and decoding JBIG data streams, along with +documentation. The first library, jbig.c, implements nearly all of the +options that the JBIG standard provides, but keeps the entire +uncompressed image in memory. The second library, jbig85.c, implements +only the ITU-R T.85 subset of the standard that black/white fax +machines use (single bit per pixel, no "progressive" encoding), and +keeps only three lines of the uncompressed image in memory, making it +particularly attractive for low-memory embedded applications. + +The libraries are not intended for 8-bit or 16-bit machine +architectures (e.g., old MS-DOS C compilers). For maximum performance, +a 32-bit processor is required (64-bit systems work too, of course). +On architectures with 16-bit pointer arithmetic, the full-featured +jbig.c library can process only very small images. + +Special features of the full-featured jbig.c variant: + + - 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 thread + + - 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) + + - Suitable for fax applications, satisfies ITU-T T.85 profile + + - 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. + +Special features of the light-weight jbig85.c variant: + + - Suitable for low-memory embedded applications + + - Implements only the JBIG1 subset defined in the ITU-T T.85 + profile (single bit plane, no differential layers) + + - Requires only three pixel rows of the uncompressed image to be + kept in memory + + - Handles all NEWLEN modes of operation required by ITU-T T.85 with + just a single pass over the data, automatically performing the + necessary lookahead after the last stripe + + - Codec buffers only a few bytes of arithmetic-codec data and outputs + resulting bytes or lines as soon as they are available. + +I will try to provide free support and maintenance for this software +for the foreseeable future, depending on my available time. + +Happy compressing ... + +Markus Kuhn + +-- +Markus Kuhn, Computer Laboratory, University of Cambridge +http://www.cl.cam.ac.uk/~mgk25/ || CB3 0FD, Great Britain |