Digital Watermarking For Images

With the fast development of communication technologyand multimedia technology,the spread and transaction of thedigital multimedia information become more and more con-venient. When people use internet as an important tool toexchange information, the information safe problems havebecome gradually apparent. Information hidden methods havesolved some problems of traditional cryptography, and theirapplications on the digital multimedia-digital watermarkinghave provided some effective ways to protect copyrights andmake sure the safe use of the multimedia information.To auseful watermark system, there are two key issues: one isthe security of watermark, the other is the key to thequestion that how to resolve the contradiction betweentransparency and robustness.At first, we have described the basic concept and theoryof digital watermarking in this paper, introduced theresearch backgroud and the present situation of watermark-ing, and concluded and compared the existing typicalalgorithms of digital image watermarking, according to thedifferent ways of information hiding. Based on the shortc-omings of the existing algorithms, we' ve proposed a new blindwatermarking algorithm using the technique of block SVD(Singular Value Decomposition)which can ensure image qual-ity well, and this method is robust against the attacks suchas cut, alteration, noise and JPEG and so on. Further, we'vecombined the new method with the technologies of wavelettransform and chaotic scrambling, and proposed a newcombound watermarking algorithm for images which enable bothrobust watermark and fragile watermark into one image.Finally, we have concluded what we have done in this paper,and prospect for the future work in the area of watermarking.