com.vividsolutions.jts.operation.BoundaryOp Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of JTSplus Show documentation
JTS Topology Suite 1.14 with additional functions for GeoSpark
There is a newer version: 0.1.4
/*
 * The JTS Topology Suite is a collection of Java classes that
 * implement the fundamental operations required to validate a given
 * geo-spatial data set to a known topological specification.
 *
 * Copyright (C) 2001 Vivid Solutions
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * For more information, contact:
 *
 *     Vivid Solutions
 *     Suite #1A
 *     2328 Government Street
 *     Victoria BC  V8T 5G5
 *     Canada
 *
 *     (250)385-6040
 *     www.vividsolutions.com
 */
package com.vividsolutions.jts.operation;

import java.util.*;
import com.vividsolutions.jts.algorithm.BoundaryNodeRule;
import com.vividsolutions.jts.geom.*;
import com.vividsolutions.jts.geomgraph.GeometryGraph;

/**
 * Computes the boundary of a {@link Geometry}.
 * Allows specifying the {@link BoundaryNodeRule} to be used.
 * This operation will always return a {@link Geometry} of the appropriate
 * dimension for the boundary (even if the input geometry is empty).
 * The boundary of zero-dimensional geometries (Points) is
 * always the empty {@link GeometryCollection}.
 *
 * @author Martin Davis
 * @version 1.7
 */

public class BoundaryOp
{
  public static Geometry getBoundary(Geometry g)
  {
    BoundaryOp bop = new BoundaryOp(g);
    return bop.getBoundary();
  }
  
  public static Geometry getBoundary(Geometry g, BoundaryNodeRule bnRule)
  {
    BoundaryOp bop = new BoundaryOp(g, bnRule);
    return bop.getBoundary();
  }
  
  private Geometry geom;
  private GeometryFactory geomFact;
  private BoundaryNodeRule bnRule;

  public BoundaryOp(Geometry geom)
  {
    this(geom, BoundaryNodeRule.MOD2_BOUNDARY_RULE);
  }

  public BoundaryOp(Geometry geom, BoundaryNodeRule bnRule)
  {
    this.geom = geom;
    geomFact = geom.getFactory();
    this.bnRule = bnRule;
  }

  public Geometry getBoundary()
  {
    if (geom instanceof LineString) return boundaryLineString((LineString) geom);
    if (geom instanceof MultiLineString) return boundaryMultiLineString((MultiLineString) geom);
    return geom.getBoundary();
  }

  private MultiPoint getEmptyMultiPoint()
  {
    return geomFact.createMultiPoint((CoordinateSequence) null);
  }

  private Geometry boundaryMultiLineString(MultiLineString mLine)
  {
    if (geom.isEmpty()) {
      return getEmptyMultiPoint();
    }

    Coordinate[] bdyPts = computeBoundaryCoordinates(mLine);

    // return Point or MultiPoint
    if (bdyPts.length == 1) {
      return geomFact.createPoint(bdyPts[0]);
    }
    // this handles 0 points case as well
    return geomFact.createMultiPoint(bdyPts);
  }

/*
// MD - superseded
  private Coordinate[] computeBoundaryFromGeometryGraph(MultiLineString mLine)
  {
    GeometryGraph g = new GeometryGraph(0, mLine, bnRule);
    Coordinate[] bdyPts = g.getBoundaryPoints();
    return bdyPts;
  }
*/

  private Map endpointMap;

  private Coordinate[] computeBoundaryCoordinates(MultiLineString mLine)
  {
    List bdyPts = new ArrayList();
    endpointMap = new TreeMap();
    for (int i = 0; i < mLine.getNumGeometries(); i++) {
      LineString line = (LineString) mLine.getGeometryN(i);
      if (line.getNumPoints() == 0)
        continue;
      addEndpoint(line.getCoordinateN(0));
      addEndpoint(line.getCoordinateN(line.getNumPoints() - 1));
    }

    for (Iterator it = endpointMap.entrySet().iterator(); it.hasNext(); ) {
      Map.Entry entry = (Map.Entry) it.next();
      Counter counter = (Counter) entry.getValue();
      int valence = counter.count;
      if (bnRule.isInBoundary(valence)) {
        bdyPts.add(entry.getKey());
      }
    }

    return CoordinateArrays.toCoordinateArray(bdyPts);
  }

  private void addEndpoint(Coordinate pt)
  {
    Counter counter = (Counter) endpointMap.get(pt);
    if (counter == null) {
      counter = new Counter();
      endpointMap.put(pt, counter);
    }
    counter.count++;
  }

  private Geometry boundaryLineString(LineString line)
  {
    if (geom.isEmpty()) {
      return getEmptyMultiPoint();
    }

    if (line.isClosed()) {
      // check whether endpoints of valence 2 are on the boundary or not
      boolean closedEndpointOnBoundary = bnRule.isInBoundary(2);
      if (closedEndpointOnBoundary) {
        return line.getStartPoint();
      }
      else {
        return geomFact.createMultiPoint((Coordinate[]) null);
      }
    }
    return geomFact.createMultiPoint(new Point[]{
                                     line.getStartPoint(),
                                     line.getEndPoint()
    });
  }
}

/**
 * Stores an integer count, for use as a Map entry.
 *
 * @author Martin Davis
 * @version 1.7
 */
class Counter
{
  /**
   * The value of the count
   */
  int count;
}