A Semi-Blind Reference Watermarking Scheme Using DWT-DCT-SVD for Copyright Protection

In this paper we propose a semi-blind watermarking scheme using Discrete Wavelet Transform, Discrete Cosine Transform and Singular Value Decomposition for copyright protection. We used a gray scale image as a watermark to hide in another gray scale image as a cover image. The cover image is modified (Zig-Zag) and divided to number of blocks of size n x n. We find the spatial frequency of each block and kept a threshold on this spatial frequency to form a reference image. Then the reference image is transformed into wavelet domain. A DCT is applied to the HF band of DWT decomposition reference image. We hide the watermark into reference image by modifying the singular values of transformed DCT coefficients with the singular values of watermark. The proposed algorithm provides a good imperceptibility and robust for various attacks.