Color opponency watermarking scheme for digital images
Sebastiano Battiato, Dario Catalano, Giovanni Gallo, Rosario Gennaro · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2000
In this paper we present a novel watermarking scheme to generalize a previous proposal by the same authors. In that paper to watermark, the image amounts to process the colors in the picture as points in the Color Opponency space and to offset each one of them by a random vector. As an extra constraint, in order to avoid picture quality degradation, the offset applied should be such that a color is not moved outside of a small sphere. The watermarking algorithm processes the colors in the picture as points in the Color Opponency space and offsets each one of them, inside a suitable imperceptive area, by a random vector. To improve robustness we suggest to partition the whole pixels population into 'color sets': each set gathers pixels with the same color. Each color set, exceeding a given cardinality, is in turn randomly partitioned into three subsets. Each one of these subsets is hence manipulated in different suitable ways. The watermark is obtained maintaining a record of the statistical distribution of the three subsets. Rigorous theoretical statistical analysis shows that this approach is robust with respect to the most common operations of image processing.