标题: 提升型离散小波转换之研究及其在影像压缩中之应用
A STUDY OF LIFTING-BASED DISCRETE WAVELET TRANSFORM AND ITS APPLICATIONS IN IMAGE COMPRESSION
作者: 苏建焜
CHIEN-KUN SU
林升甫
SHENG-FUU LIN
电控工程研究所
关键字: 离散型小波转;以物体为基础之压缩;形状方向适应型离散小波转换;提升型离散小波转换;discrete wavelet transform;object-based compression;shape-direction-adaptive DWT;lifting DWT
公开日期: 2007
摘要: 继离散型余弦转换 (discrete cosine transform; DCT) 被广泛应用于影像压缩领域之后,离散型小波转换 (discrete wavelet transform; DWT) 是目前学术界和工业界研究、发展的重点,并且已经被新一代的静态影像压缩标准 (如 JPEG2000) 和动态影像压缩标准 (如 MPEG-4,H.264/AVC) 所采用。早期的离散型小波转换其实现方式是基于回旋计算 (convolution-based) 方式,而新一代的离散型小波转换其实现方式是所谓提升型(lifting-based) 。“提升型离散小波转换” (lifting-based DWT)具有计算效率高、节省记忆空间、可执行整数至整数小波转换、适合平行处理,以及在某些场合无边界延伸的问题等优点。又因其使用上非常具有弹性,所以目前仍然是大家研究的重点。
本论文首先讨论方向适应型离散小波转换 (direction-adaptive DWT) ,然后提出应用于任意形状物体影像的提升式形状适应型离散小波转换 (lifting shape-adaptive DWT),以及可以应用于任意形状影像、且具方向适应性的形状方向适应型离散小波转换 (shape-direction-adaptive DWT;SDA-DWT)。由实验结果得知本论文提出的新方法除了保有提升型离散小波转换的优点之外,因为具有形状及方向上的适应性,故可以在有限的代价上获得影像压缩效能的显着提升。除此之外我们也讨论结合提升型离散小波转换 (lifting-based DWT) 和向量量化 (vector quantization; VQ) 来改善影像压缩效率的一些方法。
After the discrete cosine transform (DCT) was widely used in image compression, discrete wavelet transform (DWT) was the new dominated transform for research and industrial applications, and it has been adopted in the new still-image compression standards (e.g. JPEG2000) and video compression standards (e.g. MPEG-4 and H.264/AVC). In literature, the realization of DWT was convolution-based in early days, and for better computation efficiency, saving memory space, integer-to-integer transform, parallel processing, and boundary extension problem the lifting-based DWT was proposed later. Lifting-based DWT is still an important research topic, since it is more flexible than the convolution-based DWT to adopt new functionalities.
In this dissertation, the lifting-based DWT was studied, and a lifting-based direction-adaptive DWT was discussed. Then, the lifting-based shape-adaptive DWT (LSA-DWT) and the lifting-based shape-direction-adaptive DWT, which was adaptive in shape and direction, were proposed. Because SDA-DWT has the adaptabilities of shape and direction, by paying affordable cost, we can achieve superior improvement in image compression. Beside lifting-based SA-DWT and SDA-DWT, the combination of lifting-based DWT and vector quantization (VQ) was discussed in the dissertation.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT008712815
http://hdl.handle.net/11536/43223
显示于类别:Thesis


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