一种旋转、尺度变换和平移鲁棒水印算法

几何攻击是目前困扰数字水印领域发展的问题,现有的抗几何攻击的水印技术存在诸多缺陷和不足.本文提出一种基于时域的抗几何攻击水印技术,利用边框这一简单的图形通过对其检测和提取,完成对几何失真参数的检测.考虑到实际应用中存在噪声的影响,用中值滤波和锐化增加了几何参数估计的鲁棒性.利用检测获得的几何失真参数对图像进行校正,使图像基本恢复原图从而无失真地提取水印.同时本文探讨了诸多文献尚未提及的几何失真恢复问题,提出一种模板匹配的方法恢复图像.仿真实验证明,该方法在含水印图像受到几何攻击后,仍可无失真地提取水印.

A Robust Image Watermarking Algorithm against Rotation, Scaling and Translation

Geometric attack is an open problem to digital watermark.Current techniques could not solve it effectively,especially for block-based watermarking.In this paper,a new method is proposed to provide an easy-use and robust detection to geometric transform parameters.A rectangle frame in an image is utilized to estimate the coefficients of geometric attack and locate watermarking.Median filtering and sharpening on the rectangle frame are used to enable a more accurate estimation.Cropping attack is also detected by the method.The geometric distortion's correction based on the estimation results is performed to make watermark synchronized by the template matching.Experimental results verify that this method provides an accurate estimation and a nearly lossless restoration of watermark.