| Digital watermarking is a new measure of digital media protection, which are processes of embedding hidden messages within digital media such as text, images, video and audio to protect copyright. The hidden messages could be copyright information or secret messages. At the same time these messages have a very little influence on host media and have specific restore methods. These messages should be invisible to illegal receivers. This dissertation mainly focus on some key problems, such as the theoretical capacity of image DCT coefficients, embedding and detection of image watermarking, Tamper-proofing of digital media and watermark attack. Two new watermarking algorithms are presented.This dissertation mainly focus on still image watermarking, In chapter 1, the states of digital watermarking techniques are introduced and review former achievement. In chapter 2, a general digital watermarking frame is presented, including the generation, embedding and detection of watermark. In chapter 3, the concept of watermarking channel is presented, the modes of watermarking channel and image DCT coefficients is proposed, the capacity of watermarking channel is evaluated by embedding watermarks to selected still image DCT coefficients in direct spread spectrum. In chapter 4, a watermarking algorithms based wavelet multi-resolution is presented, by conjunction with human visual model, it keeps invisibility of watermark in host image and need not original image during detection. The watermarking detection is only relevant to some detail sub-images, it simplifies and accelerates the algorithm. In chapter 5, a novel fragile watermarking approach and related tamper detection are proposed, the watermark are embedded in the discrete wavelet domain of a image, it is adapt to tamper detection of digital media. In chapter 6 the current various attack methods are introduced and fully analyzed. Several directions of development of digital watermarking at next stage are proposed.
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