一种基于图像内容的半脆弱数字水印算法

本文提出了一种新的基于混沌系统的半脆弱数字水印算法，该算法将图像分成两个大小相等的部分，其中一部分用来提取基于图像特征的水印，另外一部分则用来嵌入提取的特征水印，水印嵌入在小波变换的逼近子带中。水印提取算法不需要原始图像，而且通过比较原始水印和水印图像中的特征水印与提取的水印的两个相似度，能够区分图像受到攻击的种类，算法对恶意的篡改攻击能够较好地进行定位。实验结果表明，该算法在保持对常见的JPEG压缩稳健的同时，能有效地区分偶然失真与恶意篡改。

A New Semi-fragile Watermarking Algorithm Based on Image Content

A new chaos-based semi-fragile watermarking algorithm is proposed in this paper, which first divided the total image into two parts of same size in pixel numbers, one part is used to extract image features which will be used watermarking, the other part is used to embed the watermarking extracted from the first part. The watermarking is embedded in the coefficients of low frequency of wavelet transform, and the watermarking can be extracted without resorting to the original host image. The correlation between the original watermarking and that of extracted and between the original waterrnarking and that of feature extracted from the watermarked image are used to distinguish the sort of distort imposedon image, and thetampered area of watermarked image can be reflected. Experimental results show that algorithm is robust to noise adding, compress and effective to differentiate occasional distortion from malicious tamper.