Digital watermarking of still images with color digital watermarks

Digital watermarking is a popular tool for copyright protection, content authentication, detection of illegal duplication and alteration, feature tagging and secret communication. In this paper, a method of embedding a color image as digital watermark into a host image is proposed. The watermark is first converted from the rgb color space to an index image. The index image is decomposed into a series of binary digital images for implementation as multiple watermarking. Experimental results show that the proposed method is robust to reasonable image processing operations and the lossy compression techniques such as JPEG compression. Furthermore, application of democratic approach in signal sampling is found to produce better signal to noise ratio compared with uniform quantization approach.