JTS介紹

Github項目地址：https://github.com/locationtech/jts

Maven庫地址：https://mvnrepository.com/artifact/org.locationtech.jts

JTS Topology Suite是一個用于創建和操作二維矢量幾何的Java庫。

JTS有對應的.NET版本NetTopologySuite庫，因此JTS和NTS的相關功能能夠方便地轉化和遷移（一方的功能在另一方基本都能找到對應的功能類）。

創建一個幾何，并對其進行平移、旋轉

以JDK1.8為測試環境，先通過Maven安裝JTS庫：

        <dependency><groupId>org.locationtech.jts</groupId><artifactId>jts-core</artifactId><version>1.19.0</version></dependency>

平移工具類

該平移是在原坐標x、y基礎上，分別增加一個參數dx和dy。

import org.locationtech.jts.geom.CoordinateSequence;
import org.locationtech.jts.geom.CoordinateSequenceFilter;
public class GeoOffset implements CoordinateSequenceFilter {@Overridepublic void filter(CoordinateSequence coordinateSequence, int i) {coordinateSequence.setOrdinate(i, 0, coordinateSequence.getX(i) + dx);coordinateSequence.setOrdinate(i, 1, coordinateSequence.getY(i) + dy);}private double dx;private double dy;public GeoOffset(double dx, double dy){this.dx = dx;this.dy = dy;}@Overridepublic boolean isDone() {return false;}@Overridepublic boolean isGeometryChanged() {return false;}
}

平移測試用例

    public void testGeoOffset() throws Exception {WKTReader r = new WKTReader();Geometry g = r.read("polygon((0 0,0 1,1 1,1.5 0,1 -1, 0 0))");GeoOffset geooffset = new GeoOffset(2, -0.5);g.apply(geooffset);System.out.println(g.toText());//POLYGON ((2 -0.5, 2 0.5, 3 0.5, 3.5 -0.5, 3 -1.5, 2 -0.5))}

平移前后圖形示意圖：

縮放

縮放工具類

該縮放時是在原坐標基礎上乘以一個系數scale。

import org.locationtech.jts.geom.CoordinateSequence;
import org.locationtech.jts.geom.CoordinateSequenceFilter;public class GeoScale implements CoordinateSequenceFilter {@Overridepublic void filter(CoordinateSequence coordinateSequence, int i) {coordinateSequence.setOrdinate(i, 0, coordinateSequence.getX(i) * scale);coordinateSequence.setOrdinate(i, 1, coordinateSequence.getY(i) * scale);}private double scale;public GeoScale(double scale){this.scale = scale;}@Overridepublic boolean isDone() {return false;}@Overridepublic boolean isGeometryChanged() {return false;}
}

縮放測試用例

    public void testGeoScale() throws Exception {WKTReader r = new WKTReader();Geometry g = r.read("polygon((0 0,0 1,1 1,1.5 0,1 -1, 0 0))");GeoScale geoScale = new GeoScale(2);g.apply(geoScale);System.out.println(g.toText());//POLYGON ((0 0, 0 2, 2 2, 3 0, 2 -2, 0 0))}

其他變換

可以根據需要，自定義需要的坐標變換，方法是：

先創建一個類并實現CoordinateSequenceFilter 接口，然后自定義filter函數。

例如平移時的filter函數：

    @Overridepublic void filter(CoordinateSequence coordinateSequence, int i) {coordinateSequence.setOrdinate(i, 0, coordinateSequence.getX(i) + dx);coordinateSequence.setOrdinate(i, 1, coordinateSequence.getY(i) + dy);}

旋轉時的filter函數：

    @Overridepublic void filter(CoordinateSequence coordinateSequence, int i) {coordinateSequence.setOrdinate(i, 0, coordinateSequence.getX(i) * scale);coordinateSequence.setOrdinate(i, 1, coordinateSequence.getY(i) * scale);}