Expert system for low frequency adaptive image watermarking: Using psychological experiments on human image perception

This paper proposes a new system for low frequency adaptive image watermarking based on the statistical data from psychological experiments on human image perception. The new approach can lead to a reduction of degrading the subjective image quality that often occurs when watermark is embedded into low frequency area. In order to reduce the degrading of image quality, the new approach determines the strength of watermark according to local image characteristics such as brightness and contrast. By conducting a behavioral experiment on human image fidelity based on the psycho-visual image association technique, we were able to infer the relationship between the watermark strength and the different levels of image brightness and contrast information. The exact watermark is extracted according to edge characteristics by adopting a so-called edge mask that exploits the coefficients of subbands in the subsampled discrete wavelet transform images. Thus, our new approach does not require original images for watermark. We also show the new approach is practically validated against some standard images.