JTS Geometry Operations
JTS拓扑套件是一个GeoTools的外部套件来提供一个地理信息数据结构的实现。主要的好处就是经过多年的努力在数值上是稳定的。
GooToots都是关于实现空间解决方案的，我们尽最大努力遵循一个不自己疯狂造轮子的主旨。优秀的JTS拓扑套件项目提供了我们在整个库中使用的几何实现。
GeoTools中提供了一些组件辅助JTS
- gt-api 提供了帮助类和扩展JTS的CurvedGeometryFactory工厂来处理弧线。
- gt-main 提供了帮助类来讲Geometry转换为Java形态展示。
Geometry 空间分析方法几何图形操作包：
在operation包内，包含buffer、distance、linemerge、overlap、polygonize、predicate、relate、valide八个子包；
分别对应着计算图形的缓冲、距离、线段融合、图形覆盖、多边形化、断言、关联、有效性等的操作。所有的操作针对的都是在geom包中定义的Geometry对象。
由于在计算机中，所有的图形都是离散的点组成，所以所有的操作都是在组成图形的点的集合上进行的.
一个图形(Geometry)的缓冲(buffer)
距离操作(distance)是个二元操作，操作对象Geometry A、B，返回（A）与（B）中距离最近的两个点的距离。
线段的融合(linemerge)是将Geometry A中相互连接的线段进行连接。
多边形化操作(polygonize)对Geometry A进行计算，返回一个多边形(Polygon)。将由许多个点表示的图形，用少量的点来表示，减少图形的信息，即对图形进行降维。
断言(predicate)是一个二维的操作，对Geometry之间的关系进行判断的操作。
关联(relate) 根据DE-9IM（The Dimensionally Extended Nine-Intersection Model），该方法返回两个Geometry A与B的相交矩阵IM（Intersections Matrix）。这个矩阵在计算图形关系上用到。
一、pom.xml
<properties>
<geospark.version>1.2.0</geospark.version>
<geotools.version>14.1</geotools.version>
</properties>
<dependencies>
<dependency>
<groupId>org.scala-lang</groupId>
<artifactId>scala-library</artifactId>
<version>2.11.0</version>
</dependency>
<dependency>
<groupId>org.datasyslab</groupId>
<artifactId>geospark</artifactId>
<version>${geospark.version}</version>
</dependency>
<dependency>
<groupId>org.geotools</groupId>
<artifactId>gt-geometry</artifactId>
<version>20.0</version>
</dependency>
<dependency>
<groupId>com.vividsolutions</groupId>
<artifactId>jts</artifactId>
<version>1.13</version>
</dependency>
<dependency>
<groupId>org.json</groupId>
<artifactId>json</artifactId>
<version>20180813</version>
</dependency>
<dependency>
<groupId>com.esri.geometry</groupId>
<artifactId>esri-geometry-api</artifactId>
<version>2.2.2</version>
</dependency>
<dependency>
<groupId>org.geotools</groupId>
<artifactId>gt-geojson</artifactId>
<version>${geotools.version}</version>
</dependency>
<dependency>
<groupId>org.geotools</groupId>
<artifactId>gt-api</artifactId>
<version>${geotools.version}</version>
</dependency>
<dependency>
<groupId>org.geotools</groupId>
<artifactId>gt-referencing</artifactId>
<version>${geotools.version}</version>
</dependency>
<dependency>
<groupId>org.geotools</groupId>
<artifactId>gt-epsg-hsql</artifactId>
<version>${geotools.version}</version>
</dependency>
</dependencies>
<repositories>
<repository>
<id>osgeo</id>
<name>Open Source Geospatial Foundation Repository</name>
<url>http://download.osgeo.org/webdav/geotools/</url>
</repository>
<repository>
<snapshots>
<enabled>true</enabled>
</snapshots>
<id>boundless</id>
<name>Boundless Maven Repository</name>
<url>http://repo.boundlessgeo.com/main</url>
</repository>
</repositories>
</project>
二、JTS Geometry Operation
列举了distance,intersection,union,difference 操作：
import java.util.ArrayList;
import java.util.List;
import org.geotools.geometry.jts.JTSFactoryFinder;
import com.vividsolutions.jts.geom.Coordinate;
import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.geom.GeometryFactory;
import com.vividsolutions.jts.geom.LineString;
/**
* Description 几何对象操作
*/
public class Operation {
private GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory( null );
/**
* create a Point
* @param x
* @param y
* @return
*/
public Coordinate point(double x,double y){
return new Coordinate(x,y);
}
/**
* create a line
* @return
*/
public LineString createLine(List<Coordinate> points){
Coordinate[] coords = (Coordinate[]) points.toArray(new Coordinate[points.size()]);
LineString line = geometryFactory.createLineString(coords);
return line;
}
/**
* 返回(A)与(B)中距离最近的两个点的距离
* @param a
* @param b
* @return
*/
public double distanceGeo(Geometry a,Geometry b){
return a.distance(b);
}
/**
* 两个几何对象的交集
* @param a
* @param b
* @return
*/
public Geometry intersectionGeo(Geometry a,Geometry b){
return a.intersection(b);
}
/**
* 几何对象合并
* @param a
* @param b
* @return
*/
public Geometry unionGeo(Geometry a,Geometry b){
return a.union(b);
}
/**
* 在A几何对象中有的，但是B几何对象中没有
* @param a
* @param b
* @return
*/
public Geometry differenceGeo(Geometry a,Geometry b){
return a.difference(b);
}
public static void main(String[] args){
Operation op = new Operation();
//创建一条线
List<Coordinate> points1 = new ArrayList<Coordinate>();
points1.add(op.point(0,0));
points1.add(op.point(1,3));
points1.add(op.point(2,3));
LineString line1 = op.createLine(points1);
//创建第二条线
List<Coordinate> points2 = new ArrayList<Coordinate>();
points2.add(op.point(3,0));
points2.add(op.point(3,3));
points2.add(op.point(5,6));
LineString line2 = op.createLine(points2);
System.out.println(op.distanceGeo(line1,line2));//out 1.0
System.out.println(op.intersectionGeo(line1,line2));//out GEOMETRYCOLLECTION EMPTY
System.out.println(op.unionGeo(line1,line2)); //out MULTILINESTRING ((0 0, 1 3, 2 3), (3 0, 3 3, 5 6))
System.out.println(op.differenceGeo(line1,line2));//out LINESTRING (0 0, 1 3, 2 3)
}
}
三、 Buffer，LineMerger，Polygonization，UnionLine，凹壳分析，Overlays
构造器：GeometryFactory.java
import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.io.ParseException;
import com.vividsolutions.jts.io.WKTReader;
public class GeometryFactory {
private WKTReader reader;
private GeometryFactory instance = null;
public static synchronized GeometryFactory getInstance(){
if(instance==null){
instance = new GeometryFactory();
}
return instance;
}
public void getReader(){
reader = new WKTReader();
}
public Geometry buildGeo(String str){
try {
if(reader==null){
reader = new WKTReader();
}
return reader.read(str);
} catch (ParseException e) {
throw new RuntimeException("buildGeometry Error",e);
}
}
}
3.1 Buffer,返回的结果是一个Polygon或者 MultiPolygon
import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.operation.buffer.BufferOp;
public class Buffers {
private GeometryFactory factory = GeometryFactory.getInstance();
public Geometry buildGeo(String str) {
return factory.buildGeo(str);
}
public static void main(String[] args) {
Buffers bs = new Buffers();
String line1 = "LINESTRING (0 0, 1 1, 2 2,3 3)";
Geometry g1 = bs.buildGeo(line1);
//方式(一)
Geometry g = g1.buffer(2);
////方式(二) BufferOP
BufferOp bufOp = new BufferOp(g1);
bufOp.setEndCapStyle(BufferOp.CAP_BUTT);
Geometry bg = bufOp.getResultGeometry(2);
}
}
3.2 Polygonization 面处理类
import java.util.ArrayList;
import java.util.List;
import java.util.Collection;
import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.operation.polygonize.Polygonizer;
public class Polygonization {
private static GeometryFactory factory = GeometryFactory.getInstance();
public static void main(String[] args) {
List<Geometry> list = new ArrayList<Geometry>();
list.add(factory.buildGeo("LINESTRING (0 0,1 1)"));
list.add(factory.buildGeo("LINESTRING (6 3,6 10)"));
list.add(factory.buildGeo("LINESTRING (2 2,4 4,6 3)"));
list.add(factory.buildGeo("LINESTRING (2 2,5 1,6 3)"));
list.add(factory.buildGeo("LINESTRING (6 3,6 4)"));
list.add(factory.buildGeo("LINESTRING (9 5,7 1,6 4)"));
list.add(factory.buildGeo("LINESTRING (9 5,8 8,6 4)"));
Polygonizer p = new Polygonizer();
p.add(list);
Collection<Geometry> polys = p.getPolygons(); //面
Collection<Geometry> dangles = p.getDangles();//悬挂线
Collection<Geometry> cuts = p.getCutEdges(); //面和面的连接线
System.out.println(polys.size()+":"+polys.toString());
System.out.println(dangles.size()+":"+dangles.toString());
System.out.println(cuts.size()+":"+cuts.toString());
}
}
输出结果：
2:[POLYGON ((2 2, 4 4, 6 3, 5 1, 2 2)), POLYGON ((6 4, 8 8, 9 5, 7 1,
6 4))] 2:[LINESTRING (6 3, 6 10), LINESTRING (0 0, 1 1)] 1:[LINESTRING
(6 3, 6 4)]
3.3 LineMerger 线路合并，线路之间不能有交点，并且只在线路末尾有公共交点
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.operation.linemerge.LineMerger;
public class MergerLine {
private static GeometryFactory factory = GeometryFactory.getInstance();
public static void main(String[] args) {
LineMerger lineMerger = new LineMerger();
List<Geometry> list = new ArrayList<Geometry>();
list.add(factory.buildGeo("LINESTRING (3 3,2 2,0 0)"));
list.add(factory.buildGeo("LINESTRING (3 3,6 6,0 10)"));
list.add(factory.buildGeo("LINESTRING (0 10,3 1,10 1)"));
lineMerger.add(list);
Collection<Geometry> mergerLineStrings = lineMerger.getMergedLineStrings();
for (Geometry g : mergerLineStrings) {
System.out.println(g.toText());
}
}
}
输出结果：LINESTRING (0 0, 2 2, 3 3, 6 6, 0 10, 3 1, 10 1)
lineMerger 和union区别，union可以在两条相交的线中生成交点(noded)
3.4 union 线路合并，并且生成交叉点
import java.util.ArrayList;
import java.util.List;
import com.vividsolutions.jts.geom.Geometry;
public class UnionLine {
private static GeometryFactory factory = GeometryFactory.getInstance();
public static void main(String[] args) {
List<Geometry> list = new ArrayList<Geometry>();
list.add(factory.buildGeo("LINESTRING (10 10,2 2,0 0)"));
list.add(factory.buildGeo("LINESTRING (10 0,6 6,0 10)"));
list.add(factory.buildGeo("LINESTRING (1 1,3 1,10 1)"));
Geometry nodedLine = list.get(0);
for (int i = 1; i < list.size(); i++) {
nodedLine = nodedLine.union(list.get(i));
}
int num = nodedLine.getNumGeometries();
for (int j = 0; j < num; j++) {
Geometry eachG = nodedLine.getGeometryN(j);
System.out.println(eachG.toText());
}
}
}