A Double-Color Image Watermarking Algorithm Based on Quaternion Schur Decomposition

In view of the fact that many watermarking algorithms used for copyright protection have ignored the correlation and synchronization between the color channels, a new quaternion Schur (QSchur) decomposition algorithm is presented in this paper. Firstly, the watermark image is encrypted by the compound chaotic map; then, the QSchur decomposition is used to associate and transform multiple color channels; finally, the watermark is embedded and extracted blindly by using the high correlation between the coefficient pairs in the block. Due to the high time complexity of the quaternion, a real structure-preserving algorithm is used to reduce the running time of the proposed algorithm. Simulation experiments and analysis demonstrate that this algorithm has stronger robustness and higher security when the actual embedding rate and invisibility are the same as those of other algorithms given