基于沃尔什-哈达玛变换和卷积编码的半脆弱水印算法

Semi-fragile watermark algorithm based on Walsh-Hadamard transformand and convolution coding

提出了一种基于沃尔什-哈达玛变换和卷积编码的半脆弱水印算法。在该算法中,对嵌入水印之前的图像进行像素块差分编码和卷积纠错编码来得到水印,并将其嵌入在沃尔什-哈达玛变换的图像能量值上;水印检测端通过检测卷积译码中产生的误码实现水印篡改定位,利用卷积译码的结果实现篡改图像的恢复。通过理论和实验分析了该算法的有效性和由此产生的误差。实验结果表明,本算法对于有损压缩具有良好的顽健性,可以精确地检测与定位篡改的图像区域,并且可以大致恢复原始图像内容。

A semi-fragile watermark algorithm based on the Walsh-Hadamard transform and convolution coding was proposed. In this algorithm, the watermark content of the host image was extracted by differential coding and convolution coding respectively based on the image block before embedding watermark, and was embedded on the energy value of the host image after Walsh-Hadamard transforming. In the case of watermark detection, the tampered place of the image was located by detecting the error bits generated by convolution decoding, and its result was used to recover the tampered image. The efficiency and the influence on the host image quality of the proposed algorithm were discussed theoretically and experimentally. The experimental results show that the proposed algorithm has high robustness against lossy com- pression, can detect and locate the place being maliciously tampered accurately and recover the lost image content roughly.