JTS Geometry合并、裁切、叠加分析等

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。

1.distance,intersection,union,difference 示例代码：

package com.mapbar.geo.jts.operation;
 
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;
/**  
 * Class Operation.java 
 * Description 几何对象操作
 * Company mapbar 
 * author Chenll E-mail: [email protected]
 * Version 1.0 
 * Date 2012-2-21 上午10:47:47
 */
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 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 points1 = new ArrayList();
		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 points2 = new ArrayList();
		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)
	}
}

2.一些高级操作， Buffer，LineMerger，Polygonization，UnionLine，凹壳分析，Overlays

package com.mapbar.jst;
 
 
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);
		}
	}
 
}

2.1 缓冲区操作：

package com.mapbar.jst;
 
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);
	}
}

bufOp.setEndCapStyle 缓冲样式的设置，总共有三种CAP_ROUND,CAP_BUTT,CAP_SQUARE 对应如下三种情况

2.2 Polygonization 

多边形化是由线条包围区域形成多边形的过程，各线段不能交叉，只能在端点接触，且完全闭合。

package com.mapbar.jst;
 
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 list = new ArrayList();
		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 polys = p.getPolygons(); //面
		Collection dangles = p.getDangles();//悬挂线
		Collection 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)]

2.3 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

package com.mapbar.jst;
 
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 list = new ArrayList();
		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 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)

2.4 union 线路合并，并且生成交叉点

package com.mapbar.jst;
 
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 list = new ArrayList();
		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());
		}
	}
}

2.5 凹壳分析  包含几何形体的所有点的最小凸壳多边形（外包多边形）

2.6 叠加操作  叠加可以用来确定任何几何图形的布尔组合

通过对两个数据进行的一系列集合运算，产生新数据的过程。叠加分析的目的就是通过对空间数据的加工或分析，提取用户需要的新的空间几何信息。
叠加分析类型包括：
交叉分析（Intersection） 交叉操作就是多边形AB中所有共同点的集合。
联合分析（Union） AB的联合操作就是AB所有点的集合。
差异分析（Difference） AB形状的差异分析就是A里有B里没有的所有点的集合。
对称差异分析（SymDifference） AB形状的对称差异分析就是位于A中或者B中但不同时在AB中的所有点的集合

	public void overlaps() throws ParseException, FileNotFoundException{
		WKTReader reader = new WKTReader(geometryFactory);
		Polygon geometry1 = (Polygon) reader.read("POLYGON((0 0, 2 0 ,2 2, 0 2,0 0))");
		Polygon geometry2 = (Polygon) reader.read("POLYGON((0 0, 4 0 , 4 1, 0 1, 0 0))");
	    OverlayOp op = new OverlayOp(geometry1,geometry2);
	    Geometry g =op.getResultGeometry(OverlayOp.INTERSECTION);//POLYGON ((2 0, 0 0, 0 1, 2 1, 2 0))
	    Geometry g2 = op.getResultGeometry(OverlayOp.UNION);
	    Geometry g3 = op.getResultGeometry(OverlayOp.DIFFERENCE);
	    Geometry g4 = op.getResultGeometry(OverlayOp.SYMDIFFERENCE);
	    PlanarGraph p = op.getGraph(); //图
	}