Quantization Based Watermarking Robust to Geometric Transformations

Taking advantage of the rotation,scale and translation invariant property of discrete Fourier transform,each watermark bit is embedded into each homocentric circles around the zero frequency term in DFT domain by quantizing the magnitude vectors of Fourier spectrum.The embedded sequence can be extracted by “majority principles” without resorting to the original unmarked image. Experimental results show that the watermark is invisible as well as robust to any combination of geometric transformations such as rotation,scaling,clipping or translation and other common image processing techniques.