Geometry關系高級操作

一些高級的操作

• 幾何形狀Geometry緩沖（buffer）
• 線段的融合(linemerge)是將Geometry A中相互連接的線段進行連接
• 多邊形化操作(polygonize)對Geometry A進行計算，返回一個多邊形(Polygon)。將由許多個點表示的圖形，用少量的點來表示，減少圖形的信息，即對圖形進行降維
• 凹殼分析,包含幾何形體的所有點的最小凸殼多邊形（外包多邊形）

相關的代碼實現

• 工廠

package com.alibaba.autonavi;


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  static GeometryFactory instance = null;
    
    public static synchronized GeometryFactory getInstance(){
        if(instance==null){
            instance = new GeometryFactory();
        }
        return instance;
    }
    
    public void getReader(){
        reader = new WKTReader();
    }
    
    public Geometry buildGeometryByWkt(String str){
        try {
            if(reader==null){
                reader = new WKTReader();
            }
            return reader.read(str);
        } catch (ParseException e) {
            throw new RuntimeException("buildGeometry Error",e);
        }
    }

}

• buffer操作

buffer在GIS中是用於計算Geometry的給定距離內包含所有點的區域的操作

package com.alibaba.autonavi;

import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.operation.buffer.BufferOp;

/**
 * bufferdemo
 * @author xingxing.dxx
 *
 */
public class BufferDemo {

    private static GeometryFactory factory = GeometryFactory.getInstance();


    public static void main(String[] args) {
        BufferDemo bs = new BufferDemo();
        String line = "LINESTRING (0 0, 1 1, 2 2,3 3)";
        Geometry g1 = factory.buildGeometryByWkt(line);
        //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);
    }
}

• Polygonization

package com.alibaba.autonavi;

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.buildGeometryByWkt("LINESTRING (0 0,1 1)"));
        list.add(factory.buildGeometryByWkt("LINESTRING (6 3,6 10)"));
        list.add(factory.buildGeometryByWkt("LINESTRING (2 2,4 4,6 3)"));
        list.add(factory.buildGeometryByWkt("LINESTRING (2 2,5 1,6 3)"));
        list.add(factory.buildGeometryByWkt("LINESTRING (6 3,6 4)"));
        list.add(factory.buildGeometryByWkt("LINESTRING (9 5,7 1,6 4)"));
        list.add(factory.buildGeometryByWkt("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();//懸掛線
        Collection<Geometry> cuts = p.getCutEdges(); //面和面的連接線
        System.out.println(polys.size()+":"+polys.toString());
        System.out.println(dangles.size()+":"+dangles.toString());
        System.out.println(cuts.size()+":"+cuts.toString());
    }
}

• MergerLine

package com.alibaba.autonavi;

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.buildGeometryByWkt("LINESTRING (3 3,2 2,0 0)"));
        list.add(factory.buildGeometryByWkt("LINESTRING (3 3,6 6,0 10)"));
        list.add(factory.buildGeometryByWkt("LINESTRING (0 10,3 1,10 1)"));
        lineMerger.add(list);
        Collection<Geometry> mergerLineStrings = lineMerger.getMergedLineStrings();
        for (Geometry g : mergerLineStrings) {
            System.out.println(g.toText());
        }
    }
}
package com.alibaba.autonavi;

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.buildGeometryByWkt("LINESTRING (10 10,2 2,0 0)"));
        list.add(factory.buildGeometryByWkt("LINESTRING (10 0,6 6,0 10)"));
        list.add(factory.buildGeometryByWkt("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());
        }
    }
}

注意點

在使用buffer的時候發現一個比較奇怪的現象

如下圖所示:link和求出的 buffer

通過檢查輸入數據，發現是因為 link的坐標是無序的，所以才出現了這個問題

                 lng                lat
1 119.53290332862665 35.392994649858394
2         119.532898          35.393353
3         119.532898  35.39335233694318

最后附上上述圖形相關的生成R語言代碼

library(rgeos)
library(leaflet)

wkt <- "POLYGON ((119.53264429320605 35.393349227408265, 119.53277114660303 35.39335111370413, 119.53293568134956 35.39335233694318, 119.53264426515858 35.39335233694318, 119.53264426515858 35.393353, 119.53265656750867 35.3934310494835, 119.53269228159844 35.39350153049857, 119.53274794422803 35.39355760849212, 119.5328181577851 35.3935938455739, 119.532896113652 35.39360672782946, 119.53297425243832 35.3935950060648, 119.53304499701589 35.39355981694096, 119.53310148727397 35.39350457275179, 119.53313824534494 35.39343463053341, 119.53315170679396 35.39335677259173, 119.5331570354206 35.39299842245013, 119.53264962183269 35.39299087726666, 119.53264429320605 35.393349227408265))"
readWKT(wkt) -> polygon

linestring <- "LINESTRING (119.53290332862665 35.392994649858394, 119.532898 35.393353, 119.532898 35.39335233694318)"
readWKT(linestring) -> line

point_str <- "POINT (119.532856 35.393564)"
readWKT(point_str) -> point

leaflet() %>% addPolygons(data = polygon) %>% addPolylines(data = line)