Copyright Protection by Watermarking for Color Images against Rotation and Scaling Attacks Using Peak Detection and Synchronization in Discrete Fourier Transform Domain

∗ This work was supported partially by the NSC 92-2422-H009-010 ABSTRACT A watermarking method for copyright protection of color images against rotation and scaling attacks is proposed. A watermark is embedded in an input image as coefficient-value peaks circularly and symmetrically distributed in a middle band of the discrete Fourier transform (DFT) domain of the input image. By detecting the peaks in the DFT domain of the resulting stego-image, the embedded watermark can be extracted for copyright proof, even after the stego-image is attacked by rotation and rescaling. Experimental results showing the effectiveness of the proposed method are also included.