Research On Still Image Compression Coding Based On Wavelet Transform

With the development of Internet and multimedia technology, it is imperative for image compression technology to have better performance to meet the requirement of the image storage and transmission. The JPEG2000 standardization process promotes the research on image compression algorithm and wavelet image compression has already been an active research field.The work of this thesis belongs to the project, "the research on high-speed image compression used in digital camera", supported by Tianjin Natural Science Foundation. Memory efficiency and complexity are of major importance on algorithm development. Therefore, the research and system design in this work have theoretical significance and practicability, which can be used in digital camera and other applications with limited memory.Based on JPEG2000 and its software implementation - JASPER, an overall software frame including main control module, encoder module and decoder module has been designed in object-oriented way, which integrates JASPER with the implementation of this algorithm as a whole.In order to perform high-speed still image compression, DSP is selected as hardware platform for its superiority in digital signal processing. An improved adaptive binary arithmetic coder adapted to line-based wavelet image compression is proposed, which runs fast, but is very sample because of the multiply-free operation and the line-based context formation. Following the algorithm above, the bit-planes coding and rate distortion optimizations under low memory and complexity are researched. Bit-planes can be classified into three coding passes, i.e. significant pass, magnitude refinement pass and cleanup pass, and these three coding passes are coded respectively. By calculating the rate distortion values of bit streams in each coding pass according to table lookup, generated code streams are quality scalable. The algorithm in this thesis reduces the memory requirement of wavelet image coding greatly while achieving acceptable compression efficiency and image quality.