Research On Digital Watermarking Algorithms Based On Discrete Fourier Transform

With the rapid development of the multimedia technique and the Internet, it becomes more and easier for the transmission, wide distribution, and access of digital data. One side, it brings people conveniences of intercommunion each other. On the other hand, it provides chances that the third party accesses and operates the multimedia product. Someone can copy and tamper the original works arbitrarily under disagree, as infringes the author's copyright. Content providers are facing with the great challenge of how to protect the property right of their digital data. As digital watermarking technology is an effective tool of copyright protection, it has gained more and more concerns.The correct and rational systematic frame is to the assurance of carrying out research on digital watermarking. Although it has made great progress in the research of robust watermarking technique, how to resist the geometric attacks is one of the most difficulties in the watermarking field. So the research of watermarking technique against geometric attacks has now become a focus. Geometric attacks are the most ordinary attacks.Geometric attacks destroy the synchronization between the image and the watermark. The basic request and the systematic frame of digital watermarking algorithms and some representative algorithms of digital watermarking are studied. The attacks to digital watermarking and the countermeasures are also studied.Fourier Transform is very important in image processing. The two-dimension Discrete Fourier Transform is the most ordinary. Analyze Fourier Transform, two-dimension Discrete Fourier Transform, Fast Fourier Transform and the applications of them on digital images.The algorithms of digital watermarking based on Discrete Fourier Transform have some merits which algorithms based on other frequency transforms haven't. Now, the algorithms of digital watermarking based on Discrete Fourier Transform either embeds watermark only in phase or embeds watermark only in amplitude. These two methods have their merits each. Embed the watermark in the phase and the amplitude simultaneity will combine their merits. A blind digital watermarking scheme based on Discrete Fourier Transform and invariant centroid, combining image preprocess and image normalization is proposed. Experiment results show that the scheme proposed in this paper is very robust to geometric distortions and general image processing techniques.