Geometric distortions resilient watermarking technique based on 2D color histogram modification

This paper presents a robust watermarking technique against geometric distortions. The proposed technique is based on the modification of the 2D color histogram. Because the histogram of an image is one of the image geometric invariant representations, if the watermark can be embedded into the histogram, it should survive to most geometric transformations. The difficulty of the watermarking based on histogram modification is that the relationship between the histogram representation and the pixel representation is not linear; therefore the distortion caused by the histogram modification cannot be measured in advance. In the proposed method, the values of the RGB bins are modified according to watermark bit sequences. The experimental results show robustness against several geometric distortions, such as rotation, scaling, affine transformation, cropping among other geometric attacks.