OPTIMIZING PERCEPTUAL SHAPING OF A DIGITAL WATERMARK USING GENETIC PROGRAMMING
Asifullah Khan, Anwar Majeed Mirza, Abdul Majid · Iranian journal of electrical and computer engineering · 2004
Embedding of a digital watermark in an electronic document is proving to be a feasible solution for copyright protection and authentication purposes. In this paper, we present an innovative scheme of perceptually shaping watermark to the cover images. A watermark is generally embedded in the selected coefficients of the transformed image using a carefully chosen watermarking strength. Choice of a good watermarking strength, to perceptually shape the watermark according to the cover image is crucial to make a tradeoff between the two conflicting properties, namely: robustness and imperceptibility of the watermark. Traditionally, a constant watermarking strength obtained from spatial activity masking and heuristics has been used for all the selected coefficients during embedding. We consider this tradeoff as an optimization problem and have investigated an evolutionary optimization technique to find optimal/near-optimal perceptual shaping function for DCT based watermarking system. The new scheme provides an excellent tradeoff between the robustness and imperceptibility and is image adaptive. Improved resistance to attacks, especially against JPEG compression of quality 7% and Gaussian noise of variance 17000 has been observed.