In this paper, we propose several adaptive methods to improve the fractal block coding (FBC) of still images. First of all, the range of the contrast scaling is adaptively selected according to its statistical property; then, we search for the best quantized value in the selected range. Then, the domain pool of the current range block is predicted using a finite-state method, which uses the information of previous best-match domain blocks and domain pools. The size of the domain pool is automatically adjusted; however, conventional studies can only determine a fixed-size domain pool. Therefore, the search process for finding the best-match domain block in our approach is more flexible. In addition, we propose a finite-state method to estimate the mean (average pixel value) of the current range block by using the means of the previous blocks. From the simulation, we achieve 0.35 dB improvement in peak signal-to-noise ratio and 10.5% reduction in bit rate compared with the basic FBC scheme. Finally, the encoding and decoding time of different FBC schemes is also evaluated for completeness.

Keywords: fractal block coding, range block, domain block, domain pool, finite-state method

Retrieve PDF document (199901_02.pdf : 297,484 bytes)

Received May 28, 1997; accepted May 12, 1998.
Communicated by Soo-Chang Pei.