Digital watermarking of still images with colour digital watermark

Abstract

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 colour image as digital watermark into a host image is proposed. The watemark is first converted from the Red-Green-Blue (RGB) colour space to an index image. The index image is decomposed into a series of binary digital images for implementation as multiple watermarking. Experimental results shows that the proposed method is robust to resonable image processing operations and the lossy compression techniques such as the Joint Photographic Expert Group (JPEG) compression. Furthermore, application of democratic approach in signal sampling is found to produce better signal to noise ratio compared with uniform quantizaton approach.