Robust image watermarking against geometrical attacks

Robustness against geometric distortion is one of the crucial important issues in watermarking. In this paper, a new singular value decomposition-discrete cosine transform (SVD-DCT) composite image watermarking algorithm that is robust against affine transformation and ordinary image processing is presented. Applying the DCT to the cover image, we map the DCT coefficients in a zigzag order and padded zeroes to obtain four frequency bands. After inverse discrete cosine transform (IDCT), watermark is embedded in low frequency image by singular value decomposition. Experimental evaluation demonstrates that the proposed algorithm is able to withstand a variety of attacks including common geometric attacks.