FuzzyPointLocator.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.operation.overlay.validate;

import java.util.*;
import com.vividsolutions.jts.geom.*;
import com.vividsolutions.jts.algorithm.*;

/**
 * Finds the most likely {@link Location} of a point relative to
 * the polygonal components of a geometry, using a tolerance value.
 * If a point is not clearly in the Interior or Exterior,
 * it is considered to be on the Boundary.
 * In other words, if the point is within the tolerance of the Boundary,
 * it is considered to be on the Boundary; otherwise, 
 * whether it is Interior or Exterior is determined directly.
 *
 * @author Martin Davis
 * @version 1.7
 */
public class FuzzyPointLocator
{
  private Geometry g;
  private double boundaryDistanceTolerance;
  private MultiLineString linework;
  private PointLocator ptLocator = new PointLocator();
  private LineSegment seg = new LineSegment();
  
  public FuzzyPointLocator(Geometry g, double boundaryDistanceTolerance)
  {
    this.g = g;
    this.boundaryDistanceTolerance = boundaryDistanceTolerance;
    linework = extractLinework(g);
  }

  public int getLocation(Coordinate pt)
  {
    if (isWithinToleranceOfBoundary(pt))
    		return Location.BOUNDARY;
    /*
    double dist = linework.distance(point);

    // if point is close to boundary, it is considered to be on the boundary
    if (dist < tolerance)
      return Location.BOUNDARY;
     */
    
    // now we know point must be clearly inside or outside geometry, so return actual location value
    return ptLocator.locate(pt, g);
  }

  /**
   * Extracts linework for polygonal components.
   * 
   * @param g the geometry from which to extract
   * @return a lineal geometry containing the extracted linework
   */
  private MultiLineString extractLinework(Geometry g)
  {
  	PolygonalLineworkExtracter extracter = new PolygonalLineworkExtracter();
  	g.apply(extracter);
  	List linework = extracter.getLinework();
  	LineString[] lines = GeometryFactory.toLineStringArray(linework);
  	return g.getFactory().createMultiLineString(lines);
  }
  
  private boolean isWithinToleranceOfBoundary(Coordinate pt)
  {
  	for (int i = 0; i < linework.getNumGeometries(); i++) {
  		LineString line = (LineString) linework.getGeometryN(i);
  		CoordinateSequence seq = line.getCoordinateSequence();
  		for (int j = 0; j < seq.size() - 1; j++) {
   			seq.getCoordinate(j, seg.p0);
   			seq.getCoordinate(j + 1, seg.p1);
   			double dist = seg.distance(pt);
   			if (dist <= boundaryDistanceTolerance)
   				return true;
  		}
  	}
  	return false;
  }
}

/**
 * Extracts the LineStrings in the boundaries 
 * of all the polygonal elements in the target {@link Geometry}.
 * 
 * @author Martin Davis
 */
class PolygonalLineworkExtracter 
	implements GeometryFilter
{
	private List linework; 
	
	public PolygonalLineworkExtracter()
	{
		linework = new ArrayList();
	}
	
	/**
	 * Filters out all linework for polygonal elements
	 */
	public void filter(Geometry g)
	{
		if (g instanceof Polygon) {
			Polygon poly = (Polygon) g;
			linework.add(poly.getExteriorRing());
			for (int i = 0; i < poly.getNumInteriorRing(); i++) {
				linework.add(poly.getInteriorRingN(i));
			}
		}
	}
	
	/**
	 * Gets the list of polygonal linework.
	 * 
	 * @return a List of LineStrings
	 */
	public List getLinework() { return linework; }
}