A hybrid DCT-SVD based robust watermarking scheme for copyright protection

A hybrid watermarking scheme exploiting the properties of the Discrete Cosine Transform (DCT) and Singular Value Decomposition(SVD) has been proposed here. A reference image is being formed from the cover image and then its singular values are modified to hide the secret information in an imperceptible way. The security is further enhanced by the zig zag scrambling of the cover image and gray scale watermarks. The robustness of the methodology against the various image processing attacks has been validated with high Normalized Cross Correlation (NCC) values. Also, the imperceptibility of the watermarked image with the original cover image comes out to be high as indicated by high achievable Peak Signal to Noise Ratio (PSNR) values.