Study On Digital Image Watermark Technology And Its Algorithm

Digital image watermark, as a branch of data hiding technology, imbeds symbol information into the protected image using the redundancy attribute of Human Visual System. As a new methodology of copyright protection of digital image, it has become a hotspot in that field recently. Because of the attributes of invisibility, robustness and safety for the imbedded information, it is possible that the quality of the imbedded image is not destroyed after imbedding operation, meanwhile the ascription of copyright of the protected image is still available after some processing. Furthermore, with the development of the Internet and electronic business, digital image watermark, as an effective complementarity for the traditional cryptography technology, is getting more and more interest now.Our work in this paper is mainly about:1. A survey of the research and the progress in the domestic and aboard field of digital image watermark and a systematic research on the various algorithm of digital watermark have been made on the basis of the large number of collective literature.2. A novel algorithm of digital image watermark for the copyright protection is proposed to solve the existing problem in current technology of digital image watermark such as uncertain purpose, abstract form of watermark and complexity in the selection of imbedded zone. In this algorithm, the intuitionistic property is assured by using the binary image as the watermark; Discrete Cosine Transform and classical edge detection algorithm are adopted to determine the imbedded zones for the watermark. It is experimentally proved that invisibility and robustness of watermark are assured by our algorithm and present algorithm fits for the copyright of digital image. Moreover further work has been made to implement our algorithm by building a complete platform of digital image watermark which is special for the copyright of digital image with its friendly interface and high value in practice. This technology has been applied for the patent, and now the initial trial is passed.3. A novel blind watermarking algorithm based on the Blind Signal Separation(BSS) is activated from the fact that the source image is often not available in practice and existing algorithm for this problem is not powerful because of the abstract form of watermark and difficulty in determining the threshold. In this algorithm, BSS and Discrete Wavelet Transform are combined: Binary image is used as watermark and is embedded into the wavelet domain to ensure the robustness and invisibility of watermark; BSS is applied in the extraction of watermark to get the watermark with definite resolution on the condition of lack of source image. It is experimently proved that our blind watermark algorithm based on BSS is satisfying.