JTS(Geometry)表示圆形
在平时工作中会涉及一些空间范围的操作,比如两个面求交集,求一个多边形的面积等等,一般都会用到JTS。JTS支持点线面的很多操作,关键字为point、linestring、polygon。
JTS没有直接表示圆的关键字,一般用一个多边形表示圆:
1,确定边数
2,画一个环线
3,根据环线生成面
public class JtsTest { private static GeometryFactory geometryFactory = new GeometryFactory(); public static Polygon createCircle(double x, double y, final double RADIUS) { final int SIDES = 32; // 确定边数 Coordinate coords[] = new Coordinate[SIDES + 1]; for (int i = 0; i < SIDES; i++) { double angle = ((double) i / (double) SIDES) * Math.PI * 2.0; double dx = Math.cos(angle) * RADIUS; double dy = Math.sin(angle) * RADIUS; coords[i] = new Coordinate((double) x + dx, (double) y + dy); } coords[SIDES] = coords[0]; LinearRing ring = geometryFactory.createLinearRing(coords); // 画一个环线 Polygon polygon = geometryFactory.createPolygon(ring, null); // 生成一个面 return polygon; } public static void main(String[] args) throws ParseException { Polygon p = createCircle(116.45224995263672, 39.988073630126955, 1); System.out.println(p); } }
接下来用openlayers看一下生成的polygon长什么样子。
<!DOCTYPE html> <html> <head> <title>WKT</title> <link rel="stylesheet" href="https://openlayers.org/en/v4.6.5/css/ol.css" type="text/css"> <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x --> <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script> <script src="https://openlayers.org/en/v4.6.5/build/ol.js"></script> </head> <body> <div id="map" class="map"></div> <script> var raster = new ol.layer.Tile({ source: new ol.source.OSM() }); var wkt = '';// 把上面生成的polygon复制到这里 var format = new ol.format.WKT(); var feature = format.readFeature(wkt, { dataProjection: 'EPSG:4326' }); var vector = new ol.layer.Vector({ source: new ol.source.Vector({ features: [feature] }) }); var map = new ol.Map({ layers: [raster, vector], target: 'map', view: new ol.View({ center: [108.560121,36.364153], projection: 'EPSG:4326', zoom: 4 }) }); </script> </body> </html>
结果如下图:
说明:
1,第一段代码来自网络其他博客,出处忘记记录,抱歉。
2,第二段代码来自openlayers官网示例,出处:http://openlayers.org/en/latest/examples/wkt.html?q=wkt