IndexedPointInAreaLocator.java

/*
 * 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.algorithm.locate;

import java.util.*;

import com.vividsolutions.jts.algorithm.RayCrossingCounter;
import com.vividsolutions.jts.geom.*;
import com.vividsolutions.jts.geom.util.*;
import com.vividsolutions.jts.index.*;
import com.vividsolutions.jts.index.intervalrtree.*;

/**
 * Determines the {@link Location} of {@link Coordinate}s relative to
 * a {@link Polygonal} geometry, using indexing for efficiency.
 * This algorithm is suitable for use in cases where
 * many points will be tested against a given area.
 * 
 * @author Martin Davis
 *
 */
public class IndexedPointInAreaLocator 
  implements PointOnGeometryLocator
{
  private IntervalIndexedGeometry index;
  
  /**
   * Creates a new locator for a given {@link Geometry}
   * @param g the Geometry to locate in
   */
  public IndexedPointInAreaLocator(Geometry g)
  {
    if (! (g instanceof Polygonal))
      throw new IllegalArgumentException("Argument must be Polygonal");
    buildIndex(g);
  }
  
  private void buildIndex(Geometry g)
  {
    index = new IntervalIndexedGeometry(g);
  }
    
  /**
   * Determines the {@link Location} of a point in an areal {@link Geometry}.
   * 
   * @param p the point to test
   * @return the location of the point in the geometry  
   */
  public int locate(Coordinate p)
  {
    RayCrossingCounter rcc = new RayCrossingCounter(p);
    
    SegmentVisitor visitor = new SegmentVisitor(rcc);
    index.query(p.y, p.y, visitor);
  
    /*
     // MD - slightly slower alternative
    List segs = index.query(p.y, p.y);
    countSegs(rcc, segs);
    */
    
    return rcc.getLocation();
  }
  
  private static class SegmentVisitor
    implements ItemVisitor
  {
    private RayCrossingCounter counter;
    
    public SegmentVisitor(RayCrossingCounter counter)
    {
      this.counter = counter;
    }
    
    public void visitItem(Object item)
    {
      LineSegment seg = (LineSegment) item;
      counter.countSegment(seg.getCoordinate(0), seg.getCoordinate(1));
    }
  }
  
  private static class IntervalIndexedGeometry
  {
    private SortedPackedIntervalRTree index= new SortedPackedIntervalRTree();

    public IntervalIndexedGeometry(Geometry geom)
    {
      init(geom);
    }
    
    private void init(Geometry geom)
    {
      List lines = LinearComponentExtracter.getLines(geom);
      for (Iterator i = lines.iterator(); i.hasNext(); ) {
        LineString line = (LineString) i.next();
        Coordinate[] pts = line.getCoordinates();
        addLine(pts);
      }
    }
    
    private void addLine(Coordinate[] pts)
    {
      for (int i = 1; i < pts.length; i++) {
        LineSegment seg = new LineSegment(pts[i-1], pts[i]);
        double min = Math.min(seg.p0.y, seg.p1.y);
        double max = Math.max(seg.p0.y, seg.p1.y);
        index.insert(min, max, seg);
      }
    }
    
    public List query(double min, double max)
    {
      ArrayListVisitor visitor = new ArrayListVisitor();
      index.query(min, max, visitor);
      return visitor.getItems();
    }
    
    public void query(double min, double max, ItemVisitor visitor)
    {
      index.query(min, max, visitor);
    }
  }

}