CDMA-based watermarking resisting to cropping
In this paper, we propose an image watermarking algorithm in DWT domain with self-synchronization, focusing on resisting to cropping attack. In embedding, the CDMA encoded watermark, concatenated by the synchronization code, is embedded into the selected DWT coefficients of the original image. During the oblivious watermarking detection, the corresponding DWT coefficients of the cropped watermarked image are relocated by self-synchronizing efficiently, and then the correlation between the extracted watermark information and the Gold sequence is analyzed. By exploiting the time-frequency localization characteristics of DWT, we reduce the computation load to search the synchronization code. The experiment results demonstrate that the thus generated watermark is robust to cropping, JPEG, Gaussian noise and other common attacks.