Question

我正在使用geotools和jts类BufferOP在我的几何周围创建一个缓冲区。在测试期间，我遇到了点几何形状的磨损结果。如果我将capstyle设置为flat，那么我的结果将始终是emty多边形。

线和面正在工作。似乎只有点有这种问题。

如果将其更改为圆形或方形参数，则会得到预期的结果。

我正在将geotools快照21与maven和Jave 8一起使用。这是我一直在使用的Maven pom文件，以及代码示例

<properties>
 <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 <maven.compiler.source>1.7</maven.compiler.source>
 <maven.compiler.target>1.7</maven.compiler.target>
 <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 <geotools.version>21-SNAPSHOT</geotools.version>
</properties>

<dependencies>
 <dependency>
  <groupId>junit</groupId>
  <artifactId>junit</artifactId>
  <version>4.11</version>
  <scope>test</scope>
 </dependency>
 <dependency>
  <groupId>org.geotools</groupId>
  <artifactId>gt-geometry</artifactId>
  <version>${geotools.version}</version>
 </dependency>
 <dependency>
  <groupId>org.geotools</groupId>
  <artifactId>gt-epsg-hsql</artifactId>
  <version>${geotools.version}</version>
 </dependency>
 <dependency>
  <groupId>org.geotools</groupId>
  <artifactId>gt-epsg-wkt </artifactId>
  <version>${geotools.version}</version>
 </dependency>

import org.geotools.geometry.jts.JTSFactoryFinder;
import org.geotools.referencing.CRS;
import org.geotools.util.factory.Hints;
import org.locationtech.jts.geom.*;
import org.locationtech.jts.io.ParseException;
import org.locationtech.jts.io.WKTReader;
import org.locationtech.jts.operation.buffer.BufferOp;
import org.locationtech.jts.operation.buffer.BufferParameters;
import org.opengis.referencing.FactoryException;
import org.opengis.referencing.crs.CoordinateReferenceSystem;
import org.opengis.referencing.operation.TransformException;
import java.io.IOException;

public class App 
{
 public static void main( String[] args ) throws ParseException, IOException, FactoryException, TransformException {


    Integer epsg= 32632;
    String wkt = "POINT (5293201.002716452 1208988.4067087262)";
    //setup geometry point in utm coordinates (meter)

    // create geometry
    CoordinateReferenceSystem crs = CRS.decode(("EPSG:"+ epsg.toString()));
    Hints hints = new Hints(Hints.CRS, crs);
    GeometryFactory geometryFactoryWKT = JTSFactoryFinder.getGeometryFactory(hints);
    WKTReader wktReader = new WKTReader(geometryFactoryWKT);
    Geometry geom =  wktReader.read(wkt);
    geom.setSRID(epsg);


    // creates BufferParameters
    BufferParameters bufferParam = new BufferParameters();

    bufferParam.setEndCapStyle(BufferParameters.CAP_FLAT);
    // if using any other parameter result is as expected
    // bufferParam.setEndCapStyle(BufferParameters.CAP_ROUND);
    bufferParam.setJoinStyle(BufferParameters.JOIN_BEVEL );
    bufferParam.setMitreLimit(5);
    bufferParam.setSimplifyFactor(0.01);
    bufferParam.setQuadrantSegments(8);


    // creates buffer geom on point with 10m distance and use set bufferParameters
    Geometry bufferGeom =  BufferOp.bufferOp(geom ,10, bufferParam);

    System.out.println(bufferGeom);
}

有人知道为什么吗？

Answer 1

看过代码，似乎可以归结为OffsetCurveBuilder如何处理端盖。（在我看来，这很合理）似乎没有为平端盖计算任何东西，并且由于一点不会产生任何东西，除了端头，对于平端盖您什么也没有。

  private void computePointCurve(Coordinate pt, OffsetSegmentGenerator segGen) {
    switch (bufParams.getEndCapStyle()) {
      case BufferParameters.CAP_ROUND:
        segGen.createCircle(pt);
        break;
      case BufferParameters.CAP_SQUARE:
        segGen.createSquare(pt);
        break;
      // otherwise curve is empty (e.g. for a butt cap);
    }
  }

将JTS BufferOP与参数capstyle flat一起使用时，点几何会产生Emty多边形

1 个答案: