/*
* 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;
import com.vividsolutions.jts.geom.Coordinate;
/**
* Computes an approximate intersection of two line segments
* by taking the most central of the endpoints of the segments.
* This is effective in cases where the segments are nearly parallel
* and should intersect at an endpoint.
* It is also a reasonable strategy for cases where the
* endpoint of one segment lies on or almost on the interior of another one.
* Taking the most central endpoint ensures that the computed intersection
* point lies in the envelope of the segments.
* Also, by always returning one of the input points, this should result
* in reducing segment fragmentation.
* Intended to be used as a last resort for
* computing ill-conditioned intersection situations which
* cause other methods to fail.
*
* @author Martin Davis
* @version 1.8
*/
public class CentralEndpointIntersector
{
public static Coordinate getIntersection(Coordinate p00, Coordinate p01,
Coordinate p10, Coordinate p11)
{
CentralEndpointIntersector intor = new CentralEndpointIntersector(p00, p01, p10, p11);
return intor.getIntersection();
}
private Coordinate[] pts;
private Coordinate intPt = null;
public CentralEndpointIntersector(Coordinate p00, Coordinate p01,
Coordinate p10, Coordinate p11)
{
pts = new Coordinate[] { p00, p01, p10, p11 };
compute();
}
private void compute()
{
Coordinate centroid = average(pts);
intPt = findNearestPoint(centroid, pts);
}
public Coordinate getIntersection() {
return intPt;
}
private static Coordinate average(Coordinate[] pts)
{
Coordinate avg = new Coordinate();
int n = pts.length;
for (int i = 0; i < pts.length; i++) {
avg.x += pts[i].x;
avg.y += pts[i].y;
}
if (n > 0) {
avg.x /= n;
avg.y /= n;
}
return avg;
}
/**
* Determines a point closest to the given point.
*
* @param p the point to compare against
* @param p1 a potential result point
* @param p2 a potential result point
* @param q1 a potential result point
* @param q2 a potential result point
* @return the point closest to the input point p
*/
private Coordinate findNearestPoint(Coordinate p, Coordinate[] pts)
{
double minDist = Double.MAX_VALUE;
Coordinate result = null;
for (int i = 0; i < pts.length; i++) {
double dist = p.distance(pts[i]);
if (dist < minDist) {
minDist = dist;
result = pts[i];
}
}
return result;
}
}