DWT-SVD based Semi-Blind Digital Image Watermarking

With development of digital multimedia technology and rapid growth of the Internet، illegal copy and exchange of digital multimedia sources is also spread. In such environment، copyright protection plays an essential role. In this paper a new semi- blind image watermarking algorithm for proof of ownership is proposed. At first، the original image is transformed to transform domain and the low frequency sub-band is selected to make reference image. Then، 1-level wavelet decomposition is applied to reference and grey-scale watermark images. Finally، the embedding is done by modifying the singular values of reference image’s sub-bands with the equivalent singular values of watermark’s sub-bands. In the proposed method، the reference image is needed during the extraction process، so it is called semi blind method. Robustness of the proposed method against various attacks that are applied to the watermarked image is investigated. The experimental results show that the proposed method is more robust than previous works against different attacks and the watermarked image looks visually identical to the original image.