Digital Image Watermarking Technology And Its Algorithms

With the fast development of Internet and multimedia, digital watermarking, an effective way of copyright protection has already been paid attention by more and more people. Whereas the maturity of the wavelet technology and its advantage in image processing field, a deep research of digital image watermarking technology based on wavelet domain is done in this paper.Primarily, the classifications and utilized fields of digital watermarking have been simply introduced in this dissertation. On this basis, the concept of digital watermarking has been introduced, and the basic frame of digital watermarking has been explained from three fields of generating, embedding, and detecting. After some current main digital image watermarking algorithms are summarized, the attack and performance evaluation methods of digital watermarking are discussed. Then, the basic theory and method of wavelet are presented, including MRA and the wavelet decomposition and reconstruction, especially in the field of digital image watermarking. In the view of current research status and problems, we focus on how to select the location of the watermark, how to adopt embedded strategies and blind extracting method.An effective blind watermarking scheme based on wavelet tree quantization is proposed. We select the horizontal and vertical sub-bands as the watermark embedded areas, and the watermark bits are embedded according to different strategies, there exists a large different while embedding watermark bit 1 and watermark bit 0. It does not require any original image or watermark during the watermark extracting. Moreover, by designing an adaptive threshold value in the extraction process, our method is more robust for resisting common attacks such as compressing, media filtering, and Gaussian noise. Experimental results show that our method has good transparency, and the watermark can be effectively extracted even after either an unintentional or intentional image attacks.