Analyzing the Effect of Psychovisual Thresholding of DCT Coefficients for Improved Robustness of a Blind Watermarking Technique

This paper presents a blind and robust watermarking technique that exploits the advantage of the inter-block correlation property of the DCT coefficients and psychovisual thresholding of the DCT coefficients to obtain high robustness and better imperceptibility. The two coefficients of succeeding blocks at different positions based on the psychovisual threshold are chosen after applying (8×8) block-wise DCT to the original cover image, and then the mean between them is computed. To embed a watermark bit, the values of two selected coefficients are modified to bring the mean to the predetermined zone. Simulation results confirm that the proposed watermarking scheme is blind and robust and provides good visual quality watermarked images. Compared to the state-of-the-art methods, our method is more imperceptible as it raises the PSNR upto 1.83 dB and is also more robust as the robustness against various image processing and geometric attacks and JPEG image compression attacks is improved upto 7% and 12%, respectively.