GIS矢量数据的自适应水印研究

Study on Adaptive Watermark of GIS Vector Data

针对G IS矢量数据水印技术的应用现状和需求,本文根据G IS矢量数据要素类型、存储格式、冗余起始位等方面的多样性及基于行政(自然)区划分块的应用特点,提出双重嵌入的自适应水印算法:点图层基于行政(自然)区划分块自适应嵌入、提取水印;线、面图层按顶点顺序自适应嵌入、提取水印。另外,由于G IS矢量数据点图层数据存储"无序"的特点,决定了数据受调序攻击时水印标记易被破坏,而数据精度并不会遭受任何影响,因此,对点图层,需基于空间关系与位置进行数据排序预处理,从而实现水印的有序嵌入与提取。最后,本文从差异性定义出发,通过空间分析操作,判断面向G IS矢量数据水印系统的不可感知性。实验表明双重嵌入的自适应水印算法具有较好的不可感知性和鲁棒性。

Aiming at the current application and requirement of watermark technology on GIS vector data, this article proposes a double embedded auto-adapted watermark algorithm （DEAWA） for the vector digital mapping, which is based on the applied characteristic of administrative or physical division, and the various aspects of GIS vector data such as element style, data format and redundant initiation position. The DEAWA means that, once for point layer, the algorithm used for adaptive embedding and extracting is based on administrative （or physical） regionalization and for polyline or polygon layer, the algorithm is based on feature. This algorithm can automatically sense the carrier and adaptively adjust the intensity and the location of the watermark. However, because of the disordered point storage in GIS vector data, the watermark can be easily destroyed but the data precision keeps un- affected when the storage sequence of points is aggressively adjusted. Therefore, in order to avoid such invalid sequence, the DEAWA can be improved by using spatial relationship and position to arrange the point sequence in advance so that the watermark can be orderly embedded and extracted. Finally, according to the definition of difference, this article judges the imperceptibility of watermark algorithm for the GIS vector data through the operation of spatial analysis. The experiments show that the DEAWA possesses excellent imperceptibility and robustness.