Robust DFT-Domain Digital Watermarking Based on Image Normalization

In image watermarking,the watermark′s vulnerability to geometric attacks has long been a difficult problem.In this paper,a Discrete Fourier Transform(DFT) domain robust digital watermarking algorithm based on image normalization is proposed.Firstly,the geometrically invariant space is constructed by using image normalization,and a significant region is obtained from the normalized image by utilizing the invariant centroid theory.Then,the significant region is cut into blocks of 8*8,and DFT is performed on the image blocks.Finally,the digital watermark is adaptively embedded into the significant region by quantizing the magnitude and phase of the selected middle-frequency DFT coefficients.Especially,the predistortion compensation technique is used to reduce image distortion generated by image normalization.Experimental results show that the proposed scheme is not only invisible and robust against common signals processing such as sharpening,noise adding,and JPEG2000 compression,but also robust against the geometric distortion such as rotation,translation,scaling,row or column removal etc.