摘要
针对基于几何运算的图形要素拾取精度较低的问题,提出了一种基于虚拟倒序绘制-像素着色检测的图形要素拾取方法。该方法通过建立虚拟屏幕,倒序绘制欲查询的目标层的图形要素,每绘一个图形要素,检测鼠标点击的像素是否被着色,从而实现图形要素拾取。该方法不仅能够精确地拾取简单点要素、线要素、面要素、文字要素,而且对于各种复杂的地理符号仍然有效;并易推广到拉线拾取、框拾取、多边形拾取等多种拾取方式。与地理信息系统(GIS)的基于几何计算拾取的方法相比,具有思想简单、拾取精准、方法通用、实现方便等优点。编程证实该方法拾取精度优于Arc GIS、Map Info、Map GIS,达到了Auto CAD的拾取精度。
Concerning the problems that popular pickup methods in Geographic Information System（ GIS） based on geometric calculations are inefficient, this paper presented a graphic feature picking method based on virtual draw in reverse order-pixel color detection. The principle of the method is that the graphic feature on screen to be picked up is a drawn result by ＂oil painting method＂ to the pixels on the screen, i. e. previously painted graphic features will be covered by later painted.The implementation process is to virtually draw graphic features of queried layer in reverse order on a virtual screen memory block. When painting a graphic feature, the pixel was detected if being colored corresponding to the mouse click. If the pixel was colored, the graphic feature was to be picked, and exited from the loop. This method can pick up point features, line features, polygon features and text features. It can be used to pick up various symbols features by calling an external symbol library. It can also be extended to the polyline-pickup, box-pickup and polygon-pickup modes. This method is simple,precise, universal and easy to implement. Programming confirms that this method is better than Arc GIS, Map Info and Map GIS in accuracy, reaching to Auto CAD picking accuracy.
出处
《计算机应用》
CSCD
北大核心
2014年第A02期243-245,252,共4页
journal of Computer Applications
基金
国家自然科学基金资助项目(41272367)
国土资源部地质信息技术重点实验室开放基金资助项目
关键词
要素拾取
虚拟绘制
内存位图
颜色检测
地理信息系统
feature pickup
virtual draw
memory bitmap
color detection
Geographic Information System （GIS）
