基于小波变换系数去冗余的图像无损压缩方法

This paper conducts an in depth research in the applications of lossless image compression based on the combination of DPCM and integer wavelet algorithm. The former research shows that redundancy still exists in the residual coefficients after image block integer wavelet transform (IWT). Under this phenomenon, the transformed data can be compressed further if an analysis of these redundant data is carried out before the differential pulse code modulation (DPCM) coding. The redundant information is mainly distributed in the horizontal, vertical and diagonal directions because of 5/3 integer wavelet transform’s features. As a consequence, this paper proposes an algorithm of the removal of residual coefficient’s redundant information, on the basis of a large amount of experimental data. The algorithm includes constructing different prediction templates in accordance with redundant information’s distribution law, choosing the corresponding and least cost template according to the transformed sub band coefficients, removing redundant information in the residual coefficients, etc. The experimental results show that the proposed algorithm decreases the average code length of the residual coefficient at an average of 2.61 compared with that of the original image. What’s more, the compression ratio increases by 4.63% and 6.16% on average, respectively compared with the JPEG 2000 and the original image directly compressed by DPCM coding. Also it is very suitable for hardware implementation.