Abstract: Although fractal image compression has high quality at high compression ratio，it needs a lot of encoding time so that it has not been widely applied as other coding schemes in the field of image compression.In this paper，a fast algorithm for fractal image coding based on two-norm is proposed to improve this drawback.By sorting the blocks in the codebook according to their two-norms，the encoder uses the bisection search method to find out the nearest codebook block to an input range block in the sense of two-norm.After that，the encoder further visits the codebook blocks in the vicinity of the nearest codebook block in order to search out the best-matched codebook block to the range block being encoded.Computer simulation results show that the proposed scheme not only significantly reduces the encoding time，but also provides the same image quality as baseline fractal coding algorithm with full search.

Key words: fractal image coding, image compression, two-norm

摘要： 尽管分形图像压缩在高压缩比时具有高的重建图像质量，但由于它编码过程耗时而未能在图像压缩领域广泛应用。为了提高分形图像编码过程的速度，提出了基于2－范数匹配的快速分形图像编码算法，该算法先把码书里的码块按2－范数大小赋序，然后对每个输入Range块，在赋序码书中寻找与它的2－范数最接近的码块，进而在这个码块的领域内搜索Range块的最佳匹配块。计算机仿真结果显示，在不影响基本分形图像编码算法解码图像质量的情况下，该方案大大加快了它的编码速度。

关键词: 分形图像编码, 图像压缩, 2－范数