Robust watermarking of still images for copyright protection

Digital watermarking has been proposed as a means to protect the copyright of multimedia data in a networked environment, since it makes it possible to tightly embed a code into a digital document allowing the identification of the data owner. A new watermarking system for digital images is presented: the method embeds a sequence of random real numbers in a selected set of DCT coefficients. Embedding is performed by exploiting the masking characteristics of the human visual system, to ensure the watermark invisibility. The embedded sequence can be extracted without resorting to the original uncorrupted image. Experimental results demonstrate that the watermark is robust to several signal processing techniques and geometric distortions.