A color watermarking scheme in frequency domain based on quaternary coding

With the continuous development of the computer network information technique, the problem of copyright protection of color images is increasingly getting prominent. Based on above issue, this paper presents a quaternary watermarking of color image using Schur decomposition. The superiorities of the presented scheme contains three points: Firstly, the algorithm obtains the maximum eigenvalue of the pixel block using Schur decomposition that have a high efficiency, and accomplishes the hiding and blind detection of color watermark by quantifying the maximum eigenvalue to four intervals. Secondly, the algorithm uses affine transform that have high security to encrypt the location of the color watermark pixels, which improves the security of the watermarking algorithm. Thirdly, the new idea of four intervals quantization is proposed to apply to this scheme. Simulation consequences indicate that the presented scheme can satisfy the needs of visual imperceptibility, and also has large watermark capacity, strong robustness and high security.