Adaptive color watermarking

In digital watermarking, a major aim is to insert the maximum possible watermark signal while minimizing visibility. Many watermarking systems embed data in the luminance channel to ensure watermark survival through operations such as grayscale conversion. For these systems, one method of reducing visibility is for the luminance changes due to the watermark signal to be inserted into the colors least visible to the human visual system, while minimizing the changes in the image hue. In this paper, we develop a system that takes advantage of the low sensitivity of the human visual system to high frequency changes along the yellow-blue axis, to place most of the watermark in the yellow component of the image. We also describe how watermark detection can potentially be enhanced, by using a priori knowledge of this embedding system to intelligently examine possible watermarked images.