A robust watermarking algorithm based on salient image features

A feature-based robust watermarking algorithm against geometric attacks is proposed in this paper. It is well-known that geometric attacks such as rotation, scaling, and translation on a watermarked image will destroy the synchronization between the processes of watermark embedding and detection. In other words, the locations for embedding the watermark are lost due to geometric attacks, which results in the failure of watermark detection. Since salient features in an image are relatively stable under geometric attacks, they may serve as reference points to synchronize the embedding and detection processes and the detection rate of the watermark could be increased significantly. Another problem for feature-based watermarking is that the repeatability of feature detection tends to be low; that is, the features detected during the embedding process may not be detected again during the detection process. To overcome such a problem, a novel feature enhancement technique is developed to increase the repeatability rate of feature detection, in which image moments are used to achieve geometric invariance between the embedding and detection processes. Experimental results demonstrate that the proposed watermarking algorithm is able to survive various geometric attacks and common image processing operations. And the visual quality of the watermarked image is well preserved as well.