基于局部Zernike矩的RST不变水印

RST Invariant Watermark Based on Local Zernike Moments

旋转、缩放和平移(RST)等几何攻击能够破坏水印检测的同步性,而使常规水印检测失败,提出了一种基于图像局部Zernike矩的RST不变水印算法。利用图像归一化后的Zernike矩幅度具有RST不变的性质,将由Zernike矩重构的水印图像在空域嵌入原始图像的局部中,并提取该区域的Zernike矩幅度矢量作为水印矢量。水印检测时,计算局部区域的Zernike矩,并与已知Zernike矩矢量计算均方误差根(RMSE)判断水印存在与否。与使用图像全局Zernike矩相比,使用局部矩使得水印具有更好的旋转不变性,同时水印对于缩放、JPEG压缩和噪声等攻击也具有较好的检测性能。

Rotation, scaling and translation（RST） attacks can desynchronize the watermark detection so that many watermark systems fail. In this paper,a RST invariant watermark is proposed by using local Zernike moments. As the Zernike magnitude moments of a normalized image are RST invariant,the watermark image is embedded into the local area of the original image after reconstruction. And the Zernike magnitudes of the area are extracted as the eventual watermark vector. In detection, the Zernike vector of the selected area is first extracted, and the root-mean-square-error（RMSE） is employed to decide the presence of the watermark. The local Zernike moments makes the watermark more robust to rotation attacks than the global moments. The watermark is also robust to scaling as well as regular attacks such as JPEG compression and added noises.