Robust digital image watermarking method against RST attacks

Based on Radon transform and 2-D Fourier transform, this paper presents a novel digital image-watermarking scheme that is invariant to geometrical attacks like rotation, scaling and translation (RST). The watermark is embedded into the middle frequency band obtained by taking Radon transform of a circular area selected from the original unmarked image, and then extracting 2-D Fourier magnitude of this Radon transformed image. The original unmarked image is not required to extract the watermark. Furthermore, to prevent the watermarked image from degrading due to inverse Radon transform, the final watermarked image is the addition of the original image and the watermark signal obtained by inverse Radon transform. Experimental results show that the proposed scheme is robust to RST attacks.