| With the incoming and developing of digital information and network, the scope and depth of information are enhanced in great extend, the efficiency and nicety of it are improved, and the speed and simpleness of it are increased. At the same time, because the juggling becomes easier, the demands of copyright protection, content authentication and pirate tracking are put forward. It is an important issue to enforce valid copyright protection and information security in the network environment.For the strong points of imperceptions and robustness of digital watermark, it is one of techniques to solve the above issue. With the aid of National Nature Science Foundation of China(NSFC)(No. 60472044), this dissertation focuses on research on robust blind watermarking algorithms of digital image. The main works includes:(1) After plenty of references about digital watermarking are collected and read carefully, we introduces systematically some aspects of digital watermarking, such as the development background, the basic characteristic, the classification, the evaluation standard and the domestic and international research. Then, we grasp the target and the direction of the research. Finally, the thorough analysis of the generic system model of Spread Spectrum(SS) and Improved Spread Spectrum(ISS) modulation has been done.(2) In order to limit the local distortion of the watermarked images, an ISS algorithm with adaptive parameters has been proposed associated the features of Human Visual System(HVS) and block DCT. By doing this way, the watermarking scheme not only has better transparency and stronger robustness but also overcomes big local distortion existed in ISS schemes.(3) A blind digital image watermarking based on fractional correlation is presented. Linear chirps is embedded as watermark message, that is, the rates of the chirp represent watermark message such that each rate corresponds to different message. At the same time, watermarks is embedded according to adaptive... |
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