Perceptual watermarks for digital images and video

The growth of new imaging technologies has created a need for techniques th at can be used for copyright protection of digital images and video. One ap proach for copyright protection is to introduce an invisible signal, known as a digital watermark, into an image or video sequence. In this paper, we describe digital watermarking techniques, known as perceptually based water marks, that are designed to exploit aspects of the human, visual system in order to provide a transparent (invisible), yet robust watermark. In the mo st general sense, any watermarking technique that attempts to incorporate a n invisible mark into an image is perceptually based, However, in order to provide transparency and robustness to attack, two conflicting requirements from a signal processing perspective, more sophisticated use of perceptual information in the water marking process is required. It Mill describe wat ermarking techniques ranging from simple schemes which incorporate common-s ense rules in using perceptual information in the watermarking process, to more Elaborate schemes which adapt to local image characteristics based on more formal perceptual models. This review is not meant to be exhaustive; i ts aim is to provide the reader with an understanding of how the techniques hale been evolving as the requirements and applications become better defi ned.