A Digital Watermarking Algorithm Based on Subspace
Hua Zhong · Chinese Journal of Computers · 2003
As an effective technique of copyright protection, digital watermarking techniques have become a new focus of interest in recent years. In this paper, a novel digital watermarking algorithm is proposed based on the subspace principle. The watermark can be simultaneously embedded into several subspaces thus to become a multi watermark scheme. Due to the orthogonality between different subspaces, the watermarks in different subspaces are independent whose robustness remains unchanged even as the number of subspaces used for watermarking increases. According to the visual mask effect of human vision system, the watermark power control factors are properly selected to make watermark power under the just noticeable threshold, the relation between robustness and imperceptibility can be well balanced. We test the algorithm performance in the cases of single watermark, double watermarks and multi watermarks when different distortions such as JPEG compression, image resizing and cropping are applied. Experimental results show good results on image perceptual quality and watermark robustness, which verify the correctness of our analysis.