Study Of Digital Watermarking Algorithms Base On Transformation Domain

With the development of the multimedia and the network technology, the application of the digital product is more and more wide. The security of multimedia has becoming urgent problem. Of all the solution to the copyright protection, the watermarking technology is more effective one. Therefore, the study of this technology becomes a focus in the academic world.Digital Watermark is a method for imperceptibly embedding an identification code into multimedia for the purpose of proving ownership. The watermark is as one part of multimedia and strong enough to survive after some purchase.This dissertation has mainly studied digital watermarking without original image for still image. The main work includes the following three aspects:The thesis first makes a review of the related key techniques, including the basic concepts and principles of the digital watermarking and vector quantization techniques. Moreover, this thesis also summarizes the research statuses of the compressed domain watermarking and VQ based watermarking algorithms. Some of the typical algorithms are detailedly introduced and deeply analyzed in this thesis. These algorithms are the foundations of the research work in this thesis, and they also provide the basic thoughts for the research work.More and more researchers focus on meaningful digital watermarks embedding, especially, the gray-scale watermarks, because they have many good advantages but are hard to deal with. First, a simple but fast encryption algorithm of image is given in this paper which is using Arnold transformation and a fast anti-Arnold transformation, and then a gray-scale blind watermarking technique operating on DCT domain is presented, which embeds watermark information by adjusting coefficients of selected DCT block using quantization SVD.Traditional watermarking algorithms are only good for one purpose. In this paper, a kind of multi-function digital watermarking is provided, which can be applied to copyright protection and content authentication at the same time. The multipurpose watermark is divided into two parts: robust watermark and semi-fragile watermark. The robust watermark is used to provide the copyright protection of image; the semi-fragile watermark is used for authentication of the content. First, the original robust watermark and the original semi-fragile watermark are encrypted using Arnold transform, and then the original cover image is transferred by DWT. Second, we embedded the encrypted watermarks to the selected DWT coefficients. In the extraction process, there is no need for the original cover image, so we call the technique as blindly embedded algorithm.