A Geometric Attack Resistant Image Watermarking Scheme Based on Invariant Centroids

A digital image watermarking scheme that uses invariant centroids to detect and correct geometric attacks is proposed. The centroids are determined by computing a convergent geometric moment of a circular region of a predetermined size. These centroids serve as reference points for a region of interest in which a binary image is embedded using a wavelet based method and a private key to enhance robustness. In the watermark retrieval phase, the geometric attacks are estimated by identifying the centroids shift and making corrections. The centroids also help to identify the likely region in which the watermark could have been embedded. A search is performed by slightly perturbing the region of interest boundary until the highest correlation of the extracted watermark to the original watermark is obtained. Computer simulation results show that the method is effective in the retrieval of watermarks after geometric attacks. It is also robust against common signal processing attacks.