Robust Image Watermarking

By using advanced signal processing techniques, digital watermarking embeds copyright notices and the signature directly into the multimedia contents to ensure the security of the data. With the success of the Internet, digital watermarking is playing a more and more important role in the modern society. There are many urgent problems to be solved before it become practical for different purposes. Robustness is one of the key problems and robust to geometric distortion is a difficult thing in watermarking. In this paper, methods have been proposed to solve the robustness of image watermarking against geometric distortion and common signal processing. The main contributions of the paper are as follows:(1) By introducing the distance measure between images, a fast automatic resynchronization scheme has been developed. It incorporates multi-resolution matching and coarse-fine searching, achieving low computation complexity. Compared with the existing non-blind marking schemes, the major advantage of the proposed scheme is that it can cope with large amount of geometric distortion with satisfactory accuracy and it can be implemented very fast. In addition, our proposed scheme can achieve high detection accuracy. For instance, our anti-RST recovers a rotation of 0.02o. By doing so, the proposed watermarking algorithms in the DWT domain can resist RST, shearing, general linear transformation etc. The scheme can be applied to watermarking in DCT domain to resist geometric attacks as well.(2) We propose to use a training sequence embedded in the DWT domain to achieve synchronization against translation. By using the dyadic property of the DWT, we reduced the number of the DWT implementation dramatically, hence lowering the computational complexity. A new method to estimate the affine transform matrix is...