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A novel method for perceptually adaptive watermarking in image spatial domains

A novel method of watermarking in image spatial domains is proposed in this paper. The level transformation previously proposed for embedding watermark bits into each pixel of a source image is used adaptively with estimating the resulting subjective image quality. Thus, a desired subjective quality can be achieved on the watermarked image. First, the measurements of image quality by subjective evaluations are analyzed from the viewpoint of the correlation with the objective quality measures. Then, the estimating function that can yield an estimate of the subjective quality from the objective quality values is determined. By using the estimating function, the level transformation is determined in each image region so as to achieve a desired subjective image quality while increasing the capacity of embedding watermark bits. The simulation result demonstrates that the transformation is carried out in every image region adaptively according to the image texture.