7 - Lossless Image Compression

Abstract

This chapter examines a number of schemes used for lossless compression of images. It highlights schemes for compression of grayscale and color images as well as schemes for compression of binary images. Among these schemes are several that are a part of international standards. The joint photographic experts group (JPEG) is a joint ISO/ITU committee responsible for developing standards for continuous-tone still-picture coding. The more famous standard produced by this group is the lossy image compression standard. However, at the time of the creation of the famous JPEG standard, the committee also created a lossless standard. The old JPEG lossless still compression standard provides eight different predictive schemes from which the user can select. In addition, the context adaptive lossless image compression (CALIC) scheme, which came into being in response to a call for proposal for a new lossless image compression scheme in 1994, uses both context and prediction of the pixel values. The CALIC scheme actually functions in two modes, one for gray-scale images, and another for bi-level images. One of the approaches used by CALIC to reduce the size of its alphabet is to use a modification of a technique called recursive indexing. Recursive indexing is a technique for representing a large range of numbers using only a small set.