A Novel Robust Watermarking Algorithm Based on TwoLevels DCT and TwoLevels SVD

In this paper, a novel robust grayscale watermarking algorithm based on Two-Levels DCT and Two-Levels SVD is proposed. The watermark signal is (32× 32 × 8) bit gray image. First, the original image is divided into blocks according to the size of the watermark, each block corresponds to each pixel value of watermark. Second, the DCT is applied in each block twice and form new blocks. Then, SVD on the each new block to get matrices U, S and V for each block and the first value of each matrix S is collected together to form a new matrix. Apply SVD on the new matrix again to get the S matrix. The pixel value of watermark is embedded into the new S matrix through some method. And the watermark can be detected with the original image. The experimental results show that the algorithm can satisfy the transparence and robustness of the watermarking system very well. Experimental evaluation demonstrates that the proposed scheme is able to withstand a variety of attacks very well.