Stereo image watermarking method based on binocular just noticeable difference

Digital image watermarking has been proposed in order to protect the intellectual property of digital images. Although the stereo image pairs and their applications are becoming increasingly popular, very few algorithms have been proposed for copyright protection of this type of images. The existing methods do not consider the binocular visibility of stereo pairs. Due to the fact that, human perceptual system does not perceive the left and right images of stereo pairs independently, recently a binocular just noticeable difference model (BJND) is proposed. The BJND model describes the sensitivity of the human visual system to luminance changes in stereo images. In this paper, we propose a new stereo image watermarking algorithm based on BJND model. To this end, the proposed method embeds watermark in the DCT coefficients of contourlet transform. This proposed method, adaptively changes the embedding strength factor (a) according to the BJND values of two corresponding stereo blocks. Experimental results demonstrate that the proposed algorithm can achieve a tradeoff between robustness and imperceptibility, while preserving the binocular visibility threshold of stereo pairs.