Study On Image Compression System Based On Wavelet Transform

Multimedia is a new technology, which combines information in different forms, and computer technologies. Image is an important media in multimedia application. However, the limitations of transmission bandwidth and memory space make the image compression one of the key technologies in multimedia system. Based on the corelations existing in images, image compression wipes off redundant information and retains the useful information in image. Wavelet transform has been widely applied in image compression, for its favorable local characteristics of time-frequency and transform mechanism coinciding to the visual characteristics of human eyes.Compressing of image data, browsing and retrieving image effectively and precisely are two important functions of multimedia application system. In this thesis, an improved method for image coding is proposed, which is favorable for quick browsing and content_based retrieving of image. Considering the visual nature of human vision, the edges of image are extracted as an important object to process. Therefore, an improved edge feature based wavelet transform is proposed. There are two main technologies for this method: (1) a wavelet transform based on edge feature, which is different to the standard one; (2) an effective edge feature coding method. The implementations are also given.In this thesis, after having introduced the state of affairs of wavelet and its advantages, in chapter 2, information theory is introduced, and then, the necessity and feasibility of data compression for image are discussed, followed with image compression classification and the quality evaluation standard for image compression system. In chapter 3, the theory foundations, characteristics and properties of wavelet transform are introduced by the view...