Perceptual digital watermark of images using ridgelet transform

A perceptually based watermarking technique for image is proposed. It provides a new visual model, which can exactly evaluate the just noticeable distortion (JND) tolerance of human visual system. The watermarking algorithm is designed to address the issue of how to improve the robustness and the security of the embedded watermark according to the image content In order to improve the robustness and transparency, the method is first developed to determine significant ridgelet subbands and to select a couple of significant ridgelet coefficients in these subbands automatically, then the watermark bits are inserted in the visual significant ridgelet coefficients without exceeding the maximum strength of JND. With the spread of spectrum technique and the secret key protection, the security of the embedded watermark is also guaranteed very well. Experiments show that the proposed method can achieve a better tradeoff between the robustness and transparency.