一种基于系数状态表的SPIHT图像编码算法

A List of Pixel State Based SPIHT Image Coding Algorithm

提出了一种新的基于系数状态表的SPIHT(LPS-SPIHT,list of p ixel stata-set partition ing in h ierarch icaltrees)图像压缩编码算法,该算法具有以下5个特点:第一,定义了一种扩展的空间方向树,使1个结点含有2×2相邻的4个系数,并将基本EZW(嵌入式小波零树)的符号定义应用于扩展树;第二,用1个廉价的系数状态表代替了SPIHT算法中的LIS(不重要集合表)、LIP(不重要像素表)、LSP(重要像素表)等3个数据表,节省了内存;第三,通过扫描系数状态表,可一次性完成对图像数据的编码,使分类过程与细化过程合二而一;第四,利用一种树指数避免了重复计算,提高了处理速度;第五,通过重新组织编码过程,省去了对大量可推知位的编码,提高了压缩效率。实践证明,与目前公认的最为有效的SPIHT算法相比,该算法不仅性能优越,而且计算简单,容易实现。

In this paper, a new SPIHT（ set partitioning in hierarchical trees） image compression coding algorithm based on the list of pixel states（LPS-SPlHT） is presented, which has five characters as follows： Firstly, a kind of extended spatial orientation tree is defined, which makes every point include four adjacent pixels of 2 × 2, and the essential signs of EZW （embedded zerotree wavelet） is applied to the extended spatial orientation tree; Secondly, the three lists of SPIHT（ LIS, LIP,LSP） are substituted by a low-cost list of pixel states, saving the memory of program. Thirdly, the coding process is once accomplished by means of scanning the llst of pixel states, making the sorting pass and refinement pass combine to one; Fourthly, using of one tree exponent gets rid of repeading computation and then results in, the speed up of the significance judgement of trees ; Lastly, some predictable bits arc omitted from the cncoder output by rearranging the coding procedure, to reduce the redundancy of the coding and improve the compression efficiency. Practical experiments show that comparing with SPIHT algorithm which is among the best of existing coding methods, this algorithm not only has better performance, but also is easy to implement, especially, it provides a feasible referencing model for hardware design.