基于脊波变换的扩频水印算法

针对脊波变换域比小波变换域更适合表示图像线状边缘的奇异性的特征，本文设计出一种新的图像水印算法，即将图像分块脊波变换，在脊波变化域上的高频系数中加性地嵌入经零均值互不相关伪随机序列扩频调制后的水印。实验结果表明，本文算法不仅可以抵抗如压缩、加噪、滤波和剪切等各种常见攻击，还能抵抗图像灰度增强和减弱攻击，与小波域水印算法的比较也说明了本文算法的优势。

Spread Spectrum Watermarking Algorithm Based on Ridgelet Transform

A novel image watermarking algorithm was designed by taking the advantage that ridgelet transform domain is a more suitable representation of image’s linear outline edge features than wavelet transform. Firstly,the image was divided into blocks,and each block was transformed by finite ridgelet transformation. Secondly,the watermark was spread spectrum modulated by two zero mean and uncorrelated random sequences. At last,the modulated watermark was additively embedded in the high frequency coefficients of ridgelet transform domain. Experiment results show that the proposed algorithm can not only resist common attacks such as compression,noise,filtering and cropping,but also resist image gray enhancement and weakened attack. The comparison with wavelet transform domain watermarking algorithm also shows the advantages of the algorithm.