测绘学报

• 学术论文 •    

基于PostScript成像模型的线状地图符号数据结构

吴明光1,陈泰生2   

  1. 1. 南京师范大学虚拟地理环境教育部重点实验室
    2. 南京师范大学
  • 收稿日期:2010-07-06 修回日期:2010-11-02 出版日期:2011-10-25 发布日期:2011-10-25
  • 通讯作者: 陈泰生

Study on data structure of line map symbol based on PostScript

  • Received:2010-07-06 Revised:2010-11-02 Online:2011-10-25 Published:2011-10-25

摘要: 针对线状地图符号构图模式和绘制效率,分析比较了单元循环配置、线型叠加以及纯函数绘制三类典型线状地图符号数据结构优缺点。针对线状符号控制轴线几何形态复杂、多样的特点,引入了PostScript成像模型中“路径”数据结构,实现对任意复杂线状符号控制轴线的统一描述,设计了基于标记顶点序列的“路径”结构化存储方法;针对线状符号的图形特征,设计了颜色笔划、图元笔划和栅格笔划三种绘制方法,可以同时支持单元循环配置和线型叠加两种线状符号构图模式,支持卡通类、艺术类线状地图符号的设计;针对陡坎类复杂线状地图符号,设计了装饰数据结构,归纳了若干装饰规则;针对动线符号等半线半面类型线状地图符号,提出了基于轮廓变化的构造和绘制方法。线状符号数据结构由路径、笔划、装饰和轮廓变换的有限集合组成,基于此结构构建了线状地图符号设计器原型系统并进行了效率对比实验和多介质输出实验。实验表明,该数据结构能够针对线状符号的构图特点而进行灵活分解绘制,保证最优的符号绘制效率,能够支持复杂线状符号的设计,同时支持地图符号的屏幕显示、网络发布和纸质印刷。

Abstract: This paper aims at data structure of line map symbols. Firstly, graphic composition pattern and rendering efficiency in three classic structures of line symbol which contained cell-cycle, line-type overlay and function method were analyzed. Secondly, a structure and storage method based on PostScript imaging model were proposed for uniformly describing control axis in line symbols. Thirdly, three types of strokes which contained color-stroke, cell-stroke and raster-stroke were designed. They supported the two composition model of cell-cycle and line-type overlay, and could design cartoon and artistic symbols. Fourthly, an object called decoration was brought to design complex line symbols such as scarp symbol, and a rendering style based on contour transformation was proposed to support half-line & half-area symbol design as well. Any line symbol was composed of path, stroke, decoration and contour transformation. Finally, a prototype system was developed to conduct the experiments of efficiency comparison and multi-media output. Experiments show that this structure can render line symbols efficiently by decomposing them. It supports complex line symbols design and can export map symbols to computer screen for display, web for transmission and paper for printing easily.