New method for reducing boundary artifacts in block-based wavelet image compression
Jianxin Wei, Mark R. Pickering, Michael R. Frater, J.F. Arnold · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2000
The wavelet transform is usually performed on a whole image. However when the amount of memory available for the transformation is limited, the input image is partitioned into non-overlapping blocks and then each block is processed independently. Quantization, that typically follows the transformation procedure in a compression system, inevitably introduces distortion, which becomes especially pronounced along the boundaries of the blocks. In this paper we show that a significant reduction in these block boundary artifacts can be achieved by choosing odd block sizes given by 2N + 1 rather than the conventional even block sizes given by 2N. We show that, for the same coefficient entropy, an image compressed using 17 X 17 blocks of wavelet coefficients has at least 1 dB higher PSNR than an image compressed using 16 X 16 blocks of wavelet coefficients.