LZW无损压缩算法的研究与改进

Research and Improvement on LZW Lossless Compression Algorithm

研究了数据压缩技术领域中一种较有效的无损压缩算法——LZW。LZW的原理在于用字典中词条的编码代替被压缩数据中的字符串。因此字典中的词条越长越多,压缩比就越高。加大字典的容量可以提高压缩比。但字典的容量要受到计算机内存的限制,而且其字典也存在被填满的可能。这样当字典不能再加入新词条后,过老的字典就不能保证高的压缩比。为了解决这个问题,设计并实现了一种改进算法;分析了改进算法对复杂度的影响,并选用一些典型文件对改进后的算法进行了应用测试。测试结果表明,改进后的算法具有较好的压缩比和较理想的压缩效率。

Researches one kind of effective lossless compression algorithm in the data compression area of technology -- LZW. The LZW principle lies in the entry code replaces by the string of character in the packed data. Therefore in the dictionary entry is longer are more, the compression ratio is higher. Enlarges the dictionary capacity to be possible to enhance the compression ratio. But the dictionary capacity is limited by the computer memory, moreover it is possible to fill up the dictionary. After like this when the dictionary can＇ t join the new entry again, the excessively old dictionary can＇ t guarantee the high compression ratio. In view of the LZW algorithm＇ s question, we designed and implemented one kind of improved algorithm; After analyzed the effect of improved algorithm on the complexity, selected some typical documents to test the algorithm on the application. The test result indicated that the improved algorithm has the good compression ratio and the ideal efficiency of compression.