REGION-BASED FRACTAL COMPRESSION FOR STILL IMAGE
Yung-Ching Chang, Bin-Kai Shyu, Jia-Shung Wang
Department of Computer Science, National Tsing Hua University,
Hsinchu, Taiwan 30043, Republic of China
e-mail: dr804339@cs.nthu.edu.tw (Yung-Ching Chang)
jswang@cs.nthu.edu.tw
(Jia-Shung Wang)
ABSTRACT
Fractal image coding is a novel and attractive technique for still image
compression. By utilizing the characteristic of self-similarity, an iterated
function system can automatically converts an image into a set of affine
transformation coefficients. However, the conventional block-based segmentation
methods inadequately satisfy the natural image property and thus can’t
achieve an efficient performance. In this paper, we propose a thorough
fractal image compression system to approach the target of very low bit-rate.
To more efficiently utilize the property of natural images, an image dependent
region-based segmentation technique is proposed. This region-based process
consists of two steps: First, we improve the performance of quadtree decomposition
by utilizing the adaptive threshold method. Second, a merging scheme is
introduced to the result of quadtree decomposition that combines several
similar blocks into a small number of regions. We also provide a quadtree-based
segmented chain code to efficiently record the contours of the regions.
Moreover, a post-processing algorithm is applied according to region-based
segmentation to eliminate the blocking artifact. The experimental results
indicate that the proposed method has the potential to achieve comparable
extreme low bit rate among the existing method at the same level of quality.
Keywords: fractal image compression, region-based method,
very low bit-rate.