A blind color image watermarking scheme with variable steps based on Schur decomposition

The widespread application of the Internet makes the protection of image copyright face serious challenges. For resolving this problem, this paper designs a blind color digital image watermarking algorithm which meets the requirements of invisibility, security and robustness. The advantages of the proposed method include the following two points: 1) the proposed method uses Affine transformation with large key space to encrypt the watermark information; 2) Schur decomposition with low complexity is selected and performed on the matrix blocks in different color channels of the host image. In this proposed method, the watermark embedding and blind extraction are completed by quantizing the eigenvalues on the diagonal of the decomposed matrix with different quantization steps. Experimental results show that the proposed method not only has good invisibility, but also has high security and strong robustness.