Image watermarking resistant to global geometrical attacks

Robustness, especially to geometrical distortions is the present problem unresolved in the digital watermarking field. We describe an adaptive watermarking algorithm based on quantization in the DFT domain, which is robust to global geometrical distortions. The watermark was composed of a chaotic sequence, and it was embedded in the magnitudes of the DFT, and the embedded positions were the circle in the centered frequencies. The embedding strength adjusted to the properties of the original image. Watermark extraction was implemented without the original image. Experimental results show that our watermarking scheme is robust to global geometrical attacks, such as scaling, translation and rotation.