A Blind Chaos-Based Complex Wavelet-Domain Image Watermarking Technique

This paper presents a watermarking procedure for digital image in the Complex Wavelet Domain. First, a watermark image as copyright sign is preprocessed with a random location matrix. In this scheme, we apply the DT-CWT transform only locally, we transform the subimage, which is extracted from the original image, in the complex wavelet domain by using DT-CWT, then, according to the characteristics of the subimage data, the preprocessed watermark image is adaptively spread spectrum and added into the host subimage DT-CWT coefficients. The proposed watermark algorithm needs three keys: a subimage, a random location matrix and spread spectrum watermark. The first and the second ones ensure the security of watermarking procedure and the third one guarantees its robustness. Simulation results demonstrate the robustness of our image watermarking procedure, especially under the typical attacks of geometric operations.