关键词: 图像压缩, 分形, 迭代函数系统, 分形图像编码, 半范数

Abstract: Fractal image coding requires traditionally a very long runtime，which is mostly spent on searching for the best matched block to an input range block in a usually large domain pool.Based on the cross-trace algorithm proposed by these authors，a fast algorithm is proposed in this paper.It utilizes a newly-defined feature，i.e.，a semi-norm of normalized block，to confine the search space to the vicinity of the initial matched block（i.e.，the domain block having the closest semi-norm to that of the input range block being encoded）.The experiments show that the proposed algorithm performs better in terms of encoding time and image quality，compared with the cross-trace algorithm.

Key words: image compression, fractal, iterated function system, fractal image coding, semi-norm