基于PostScript成像模型的线状地图符号数据结构

摘要

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 celt-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, cellstroke 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. 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.%针对线状地图符号构图模式和绘制效率，分析比较单元循环配置、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。引入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，设计基于标记顶点序列的“路径”结构化存储方法；设计颜色笔划、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；构建线状地图符号设计器原型系统并进行效率对比和多介质输出试验。试验表明，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。