Media Laboratory, Samsung Data Systems Co, Ltd., Seoul 135-080, Korea.
IEEE Trans Image Process. 1998;7(5):632-48. doi: 10.1109/83.668022.
We present a region adaptive subband image coding scheme using the statistical properties of image subbands for various subband decompositions. Motivated by analytical results obtained when the input signal to the subband decomposition is a unit step function, we analyze the energy packing properties toward the lower frequency subbands, edges, and the dependency of energy distribution on the orientation of the edges, in subband decomposed images. Based on these investigations and ideal analysis/synthesis filtering done in the frequency domain, the region adaptive subband image coding scheme extracts suitably shaped regions in each subband and then uses adaptive entropy-constrained quantizers for different regions under the assumption of a generalized Gaussian distribution for the image subbands. We also address the problem of determining an optimal subband decomposition among all possible decompositions. Experimental results show that visual degradations in the reconstructed image are negligible at a bit rate of 1.0 b/pel and reasonable quality images are obtainable at rates as low as 0.25 b/pel.
我们提出了一种基于统计特性的区域自适应子带图像编码方案，适用于各种子带分解。受子带分解输入信号为单位阶跃函数时得到的分析结果的启发，我们对子带分解后图像中的低频子带、边缘以及能量分布对边缘方向的依赖性进行了分析。基于这些研究和频域中的理想分析/合成滤波，该区域自适应子带图像编码方案在每个子带中提取适当形状的区域，然后在图像子带的广义高斯分布假设下，针对不同区域使用自适应熵约束量化器。我们还解决了在所有可能的分解中确定最佳子带分解的问题。实验结果表明，在比特率为 1.0 b/pel 时，重建图像的视觉退化可以忽略不计，而在低至 0.25 b/pel 的速率下，仍可以获得合理质量的图像。
