2-D Walsh coding for robust digital image watermarking

One-dimensional (I-D) 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 (2-D) Walsh coding to achieve further improvements in robustness. In the proposed method, Walsh functions are used to perform 2-D 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 2-D Walsh coding results in improved robustness against JPEG compression attacks compared to 1-D 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.