Copyright Protection and Authentication of Grayscale Images by Removable Visible Watermarking and Invisible Signal Embedding Techniques: A New Approach*

A novel method for copyright protection and authentication of grayscale images is proposed. The involved techniques include a human visual model, least significant bit replacement, and reversible pixel color adjustment. These techniques are integrated effectively to embed a visible watermark and authentication signals into the single grayscale channel of the image. The copyright of the image can be proved by extracting the embedded watermark. And the integrity of the image can be proved by verifying the existence of the embedded authentication signals. Besides, the embedded visible watermark can be removed, if desired, so that only the watermarked image need be kept, providing an advantage of storage space saving. Some experimental results are shown to prove the feasibility of the proposed method.