Research Of Digital Image Adaptive Compression

This thesis makes research on adaptive compression for static image and motion image.Research on adaptive compression algorithm for static image probes into an adaptive-quantization(AQ) method based on the previous compression research about adaptive-partition(AP), and then brings forward an adaptive compression algorithm which combines AQ and AP. In frequency domain, the distribution of image energy is characterized by its special coefficients and their positions. In Discrete Consine Transform domain smooth area has more important coefficients centralized in low frequency section and more ignorable unimportant coefficients than unsmooth area. With larger amount of experiments we find the AQ and the following entropy coding to important coefficients and their addresses using statical law can obtain a larger ratio and a better reconstructed vision effect in unsmooth area. Experimental results show that compared with JPEG the proposed algorithm can greatly improve the compression ratio on the premise of same decoding image vision effect.For videos the research including three parts: (1)block's mobility-based classification by a kind of motion measurement(MM), combining block-match motion search(MS) criterion and principle of decision by majority, forms the adaptive motion compensation. Before MS, blocks are seperated into motion blocks and static blocks using the proposed MM, static block is endowed with zeros vector which will save massive computing cost, and motion block performs normal MS, (2)A frame-correlation -measurement based on block MM is used to measure frame's correlation. Setting I frame at the place of correlation decreasing greatly resulted from scene switch will restrict the group of picture(GOP) in the same scence and the frame predictive coding will perform more efficiently. (3)Using AP method to compress the remain frame after motion compensation which has many large smooth areas can improve ratio remarkably. Experiments show that on the premise of high decoding frame quality the proposed ada ptive video compression algorithm can obtain an accurate orientation for scene switch, a...