Overview of JBIG
JBIG is short for the 'Joint Bi-level Image experts Group'. This is a group of experts nominated by national standards bodies and major companies to work to produce standards for bi-level image coding. The 'joint' refers to its status as a committee working on both ISO/IEC and ITU-T standards. The official title of the committee is ISO/IEC JTC1 SC29 Working Group 1, and is responsible for both JPEG and JBIG standards.
JBIG has developed ISO/IEC 11544 (ITU-T T.82) for the lossless compression of a bi-level image. It can also be used for coding greyscale and colour images with limited numbers of bits per pixel. It can be regarded as a form of facsimile encoding, similar to Group 3 or Group 4 fax, offering between 20 and 80% improvement in compression over these methods (about 20 to one over the original uncompressed digital bit map).
JBIG2 is the successor (ISO/IEC 14492 | ITU-T T.88) format for bi-level (black/white) image compression that offers significant advantages over other compression formats:
- large increases in compression performance (typically 3-5 times smaller than Group 4/MMR, 2-4 times smaller than JBIG1)
- special compression methods for text, halftones, and other binary image content
- lossy and lossless compression
- multi-page document compression
- flexible format, designed for easy embedding in other image file formats, such as TIFF
- high-performance decompression: using some coding modes, images can be decompressed at over 250 million pixels/second in software