T-SVD-Based Robust Color Image Watermarking

In order to protect the copyright of the color image, a robust color image watermarking method based on Tensor-Singular Value Decomposition (T-SVD) is proposed. In order to preserve strong correlations of the RGB three channels of the color image, the color image is considered as the third-order tensor, which is transformed by using T-SVD to obtain two orthogonal tensors and one diagonal tensor. Since the diagonal tensor includes the main energies of the color image, it can be exploited to embed watermark for robustness. Firstly, the three channels of the color image are decomposed by using discrete wavelet transform (DWT) into four subbands, respectively, and the LL subband of each channel is used to construct an approximation image. Secondly, the approximation image is divided into non-overlapping blocks with the size of 4 × 4, and the TSVD is applied in each block to compute the first, the second and the third diagonal matrices. Finally the grayscale watermark is decomposed by using Singular Value Decomposition (SVD). The principal components of the gray-scale watermark are embedded by modifying the first diagonal matrix of each block, since the first diagonal matrix is more robust than other two diagonal matrices. Experiment results show that the proposed method can resist a variety of image attacks, and is more robust than the existing watermarking methods.