基于差分扩张和平移的2D矢量地图的可逆水印

Reversible digital watermarking scheme for 2-D vector maps based on difference expansion and shifting

利用差分平移和差分扩张,提出一种新的应用于数字矢量地图的可逆水印算法。该算法通过调整地图中的顶点坐标进行水印嵌入。与差分扩张方法不同,该算法依次计算顶点坐标序列中任意2个相邻坐标之间差分,将差分大于K-1的向右平移,差分小于-K的向左平移,差分介于-K、K-1间的进行差分扩张并嵌入水印(K是由用户所确定的正整数),同时通过适当调整顶点的坐标使得嵌入水印后差分的改动均匀分布在2个坐标上,保证了较低的数据扰动。与Wang的算法相比,该算法在保持较低变形的基础上能够嵌入更多的水印信息。

Based on the difference expansion and difference shifting,a novel reversible watermarking algorithm for digital vector map is proposed.The watermark is embedded by modifying the vertices coordinates.Instead of difference expansion,the difference of every adjacent coordinates is divided into three parts:one is shifted right if the difference is bigger than K-1;the second is shifted left if the difference is smaller than -K;and the third part is used to expand and embed the watermark (Kis a positive integer chosen by the user).At the same time,the distortion caused by expansion and shifting is uniformly separated into the two pixels,which keeps the lower distortion.Experimental results demonstrate that the proposed scheme can embed a larger payload while keeping the lower root mean square error (RMSE).