基于图像内容的脊波变换域数字水印模型和算法研究

在研究人类视觉(HVS)特性的基础上提出了一种在脊波变换域基于图像内容的数字水印模型。在此模型中，嵌入数字水印的强度归结于数字图像脊波系数的视觉掩盖效应，文中建立了脊波变换域人眼临界可见误差模型。图像的水印检测被归结为Neymann-PeaLrson准则下的统计模型，该模型被用来估算水印检测的最优阈值。作为算例，将临界可见误差模型结合扩展谱技术，提出了一种新颖的图像自适应水印算法，并给出了相应的实验结果。实验表明算法性能大幅度提高。

Research of Image Content Based Digital Watermarking Model and Algorithm in Ridgelet Transform Domain

In this paper, an image content based perceptual watermarking model using ridgelet transform is presented. 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 watermark bits are inserted in the visual significant ridgelet coefficients without exceeding the maximum strength of JND. With the spread spectrum technique and the secret key protection, the security of the embedded watermark is also guaranteed very well. Through analyzing the statistical property of the watermarked image, a threshold selection method based on Neymann-Pearson principle is presented and then the embedded watermark can be blindly detected by correlation coefficients between the original image and the watermark sequence. Experiments show that the proposed method can achieve a better tradeoff between the robustness and transparency.