Enhanced Wavelet-Based Zerotree Coding of Images

Abstract: This paper presents a wavelet based image coding method achieving high levels of compression. Our Eigen designed Quadrature Mirror Filters are implemented in a multiresolution subband decomposition system [1][2]. Symmetrical extension and windowing of the multi-scaled subbands are incorporated to minimize the boundary effects. Next, the Embedded Zerotree Wavelet [3] coding algorithm is used for data compaction method. In our experiments, the EZW coded stream can be further reduced to yield a smaller symbol string by not coding the Zero symbol in the last three subbands of the wavelet map, i. e. HLl, LHI, and HHI which leads to an improved EZWalgorithm. Additional compression is obtained with an adaptive arithmetic coder [4]. Results of coding Lena are tabulated in Table 1. Fig. I shows thatfor a low PSNR of 27.49 dB at a bit rate of 0.8554 for the Aerial image, the quality of the decoded image is visually acceptable. No blocky effects are evidenced as compared to JPEG coding technique.