Enhancing image watermarking methods by second order statistics
A pirate attack on an image aims to create an invisible modification of it. We propose a watermarking strategy which applies optimization techniques to the second order statistics of perceptually unaltered modifications of an image. The solution gives two orthogonal spaces. One of them characterizes most of the variations in the modification of the image. Our watermark is embedded in the other space that most potential pirate attacks do not touch. Thus, the embedded watermark is robust. We also show that our method is able to enhance many existing watermarking strategies. We also demonstrate the performance of our method.