Compress Compound Images in H.264/MPGE-4 AVC by Exploiting Spatial Correlation
Compress Compound Images in H.264/MPGE-4 AVC by Exploiting Spatial Correlation
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DOI：
10.1109/tip.2009.2038636
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发表时间：
2010-04
影响因子：
10.6
通讯作者：
Cuiling Lan;Guangming Shi;Feng Wu
中科院分区：
文献类型：
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作者：
Cuiling Lan;Guangming Shi;Feng Wu
复合图像是文本、图形和自然图像的组合。它们呈现出强烈的各向异性特征，特别是在文本和图形部分。这些各向异性特征常常使传统的压缩效率低下。因此，本文在H.264帧内编码的基础上提出了一种新的编码方案。在该方案中，为了更好地利用复合图像的空间相关性，开发了两个新的内部模式。第一种是残差标量量化(RSQ)模式，在这种模式下，预测内残差直接量化和编码，而不需要变换。第二种是基本颜色和索引映射(BCIM)模式，可以看作是一种自适应颜色量化。在此模式下，图像块由几种代表性颜色(称为基色)和要压缩的索引图表示。每个块通过率失真优化(RDO)从H.264中的两个新模式和先前的帧内模式中选择其编码模式。实验结果表明，对于复合图像，该方案在大多数码率下的编码效率提高了10dB以上，而对于自然图像，其编码效率保持了与H.264相当的高效性能。
Compound images are a combination of text, graphics and natural image. They present strong anisotropic features, especially on the text and graphics parts. These anisotropic features often render conventional compression inefficient. Thus, this paper proposes a novel coding scheme from the H.264 intraframe coding. In the scheme, two new intramodes are developed to better exploit spatial correlation in compound images. The first is the residual scalar quantization (RSQ) mode, where intrapredicted residues are directly quantized and coded without transform. The second is the base colors and index map (BCIM) mode that can be viewed as an adaptive color quantization. In this mode, an image block is represented by several representative colors, referred to as base colors, and an index map to compress. Every block selects its coding mode from two new modes and the previous intramodes in H.264 by rate-distortion optimization (RDO). Experimental results show that the proposed scheme improves the coding efficiency even more than 10 dB at most bit rates for compound images and keeps a comparable efficient performance to H.264 for natural images.