Robust Watermarking Algorithm Based On Transform Domain

In recent years, it is more and more convenient for people to share multimedia information because of the rapid development of Internet technology and multimedia processing technology. However, at the same time, copyright infringement and information tampering of digital information are occurring more frequently, the security of digital information is facing great challenges, the legitimate interests of owners and users of digital products have also been infringed seriously. Therefore, digital watermarking technology has been widely concerned and researched by experts and scholars. By employing digital watermarking technology, we can identify and certificate the owner of the digital products, track the operation of the digital products, control the copies of the content of digital products, certificate the authenticity and integrity of the digital products, identify and restore the altered data of the digital products. In this background, the research of digital watermarking technology has important academic significance and practical significance.Based on the analysis of a robust digital watermarking strategy, we conduct an in-depth research on robust digital watermarking algorithm based on transform domain and matrix decomposition, and have made some innovative achievements in improving the robustness, capacity and efficiency of the algorithms. The main research work includes:(1) Aiming at watermarking algorithm based on color host digital image in discrete wavelet transform domain, a DWT-SVD based algorithm has been proposed. Two-level wavelet transform and block singular value decomposition are applied in the three components--R, G and B of the color host image respectively. Employ chaotic sequence to select several couples of blocks as the embedding region. The embedding capacity and the intensity of each component are determined according to the characteristics of human visual system; Finally, every bit of the scrambled watermark are embedded into each couple of the largest singular value of the selected sub-block respectively. Experimental results show that the proposed algorithm has a good performance in imperceptibility and robustness against a variety of attacks.(2) Having proposed a novel robust digital watermarking algorithm based on DCT and two-level SVD. Firstly, the host image is devided into non-overlapping blocks of4×4pixels and apply singular value decomposition on each block. Then extract the maximum singular of each block to compose a new matrix and apply block-SVD of4×4pixels on the matrix. Finally the preprocessed watermark is embedded in the maximum singular value derived from the second SVD. Simulation results show that it has a good performance in imperceptibility and robustness, and the watermark capacity has been greatly improved compared with the first scheme.(3) Having proposed a robust watermarking algorithm based on two-level DCT and Schur decomposition. Firstly, the host image is partitioned into non-overlapping blocks of8×8pixels and each block is transformed by DCT. Then the upper-left4×4low frequency coefficients are transformed with the second level DCT and split into two matrices, then the derived real symmetric matrix is decomposed using the Schur decomposition. Finally the scrambled watermark is embedded in the eigenvalues gained through Schur decomposition. The thresholds are determined by the value of the binary watermark and meet the golden section ratio. Simulation results show that the proposed algorithm has a good performance in imperceptibility and robustness, and the efficiency has also been greatly improved on the basis of the second algorithm.