Digital watermarking of still images with gray-level digital watermarks

Digital watermarking has been presented in the literature as a technique to protect the copyright of multimedia data. But most of these literature concentrates on algorithms of embedding one-dimensional watermarks or two-dimensional binary digital watermarks. In this paper, a method of embedding a gray-level digital watermark into an image is proposed. By the stack filter threshold decomposition technique, a gray-level digital watermark is decompounded into a series of binary digital images for implementing multiple watermarking. The experimental results show that the proposed techniques are tolerant to reasonable image processing operations and the lossy compression techniques such as Joint Photographic Experts Group (JPEG).