2-D Walsh coding for robust digital image watermarking

One-dimensional (1D) Walsh coding have previously been proposed to improve the robustness of digital image watermarking techniques. In this paper, it is proposed to use two-dimensional (2D) Walsh coding to achieve further improvements in robustness. In the proposed method, Walsh functions are used to perform 2D coding of the watermark before embedding it in the original image. Simulation results, using both spatial-domain and frequency-domain techniques, indicate that the use of 2D Walsh coding results in improved robustness against JPEG compression attacks compared to 1D Walsh coding. Further improvements can also be achieved by increasing the length of the Walsh sequence. This is, however, at the expense of more degradation to the watermarked image.