A hybrid DCT-SVD based image watermarking algorithm

Everyday, people share their digital media on the virtual networks; therefore, protecting them against piracy is worthy of consideration. Digital watermarking is a method to achieve this goal. In this paper, we propose a watermarking method in Discrete Cosine Transform (DCT) domain. For this purpose, DCT coefficients of the whole image are calculated. It helps to present a system without blockiness effects. Then, singular values of the watermark image are added to the low frequency DCT coefficients of cover image that are located on the main diagonal. We use scaling factors for watermark embedding to improve imperceptibility of the watermark. A vector of fixed elements, which is calculated empirically, is used as a set of scaling factors. We embed the watermark with a four-time redundancy in the cover signal. It is helpful to take advantage of voting method for improving performance of the system in extraction phase. Experimental Results show higher performance of the proposed method in comparison with similar works in this domain.