一种鲁棒的矢量地图数字水印算法

通过仔细分析MQUAD算法的缺陷，提出一种双重嵌入的鲁棒矢量地图数字水印算法．该算法按地图内所含对象特征把矢量地图分为两层，对不同的图层采用不同算法调制水印信息到各顶点；分别计算两个图层中代表水印信息的位移量，在阈值的控制下，选择有效的顶点并计算顶点坐标平均值即得到水印信息位序列．实验结果表明，文中算法对随机噪声、扭曲变形和各种剪切具有很强的鲁棒性．

A Robust Watermarking Algorithm for Vector Digital Mapping

The MQUAD algorithm is an efficient watermarking algorithm for vector digital mapping, however several problems were found from our investigation A double embedded robust watermark scheme for vector digital mapping is then presented, as an extension to the MQUAD algorithm The vector map is subdivided into two layers by the character of objects in the map A watermark bit is embedded by two different methods in two layers of the same map After the displacements of a set of vertices are computed, the vertices with their displacements shorter than thresholds are selected, and an average of the displacements, or the watermark bit is obtained Experiments show that the watermarks are resilient to additive random noise, local deformation and several cropping