A new lossless chain code compression scheme based on substitution

A chain code is a method of representing the region boundaries of an image. It obtains a high level of data reduction and represents an image boundary in compressed form. In this paper, a new method of lossless compression of Freeman 4-directional chain codes as well as 8-directional chain codes has been proposed that brings about an average compression ratio of 50% and 80% into Freeman 4-directional and 8-directional chain codes respectively. The average space savings achieved in case of Freeman 4-directional chain codes is 50% and that achieved in case of Freeman 8-directional chain codes is 18%.