Protecting Copyrights of Color Images using a Watermarking Scheme Based on Secret Sharing and Wavelet Transform

This paper presents a novel digital watermarking scheme for copyright protection against piracy of color images. Unlike traditional watermarking schemes that directly embed watermarks into host images, the scheme encodes the watermark prior to watermark embedding to improve tolerance to attacks. The process utilizes the secret sharing scheme with the feature extracted form the host image by the discrete wavelet transform. Moreover, different from other watermarking schemes that require manual adjustment in the embedding scaling factors to embed the watermark, the scheme can automatically calculate the scaling factor for different images while still preserving robustness and imperceptibility. The experimental results show that the scheme can resist several attacks including cropping, scaling, and JPEG compression. Furthermore, the ability of extracting unique features from different images, which is an important requirement for feature extraction, is also demonstrated in the experiment.