/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2001-2006 Vivid Solutions
* (C) 2001-2008, Open Source Geospatial Foundation (OSGeo)
*
* 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;
* version 2.1 of the License.
*
* 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.
*/
package org.geotools.geometry.iso.util.algorithm2D;
import org.geotools.geometry.iso.topograph2D.Coordinate;
/**
* Represents a homogeneous coordinate in a 2-D coordinate space. In JTS
* {@link HCoordinate}s are used as a clean way of computing intersections
* between line segments.
*
* @source $URL$
*/
public class HCoordinate {
/**
* Computes the (approximate) intersection point between two line segments
* using homogeneous coordinates.
* <p>
* Note that this algorithm is not numerically stable; i.e. it can produce
* intersection points which lie outside the envelope of the line segments
* themselves. In order to increase the precision of the calculation input
* points should be normalized before passing them to this routine.
*/
public static Coordinate intersection(Coordinate p1, Coordinate p2,
Coordinate q1, Coordinate q2) throws NotRepresentableException {
HCoordinate l1 = new HCoordinate(new HCoordinate(p1), new HCoordinate(
p2));
HCoordinate l2 = new HCoordinate(new HCoordinate(q1), new HCoordinate(
q2));
HCoordinate intHCoord = new HCoordinate(l1, l2);
Coordinate intPt = intHCoord.getCoordinate();
return intPt;
}
public double x, y, w;
public HCoordinate() {
x = 0.0;
y = 0.0;
w = 1.0;
}
public HCoordinate(double _x, double _y, double _w) {
x = _x;
y = _y;
w = _w;
}
public HCoordinate(double _x, double _y) {
x = _x;
y = _y;
w = 1.0;
}
public HCoordinate(Coordinate p) {
x = p.x;
y = p.y;
w = 1.0;
}
public HCoordinate(HCoordinate p1, HCoordinate p2) {
x = p1.y * p2.w - p2.y * p1.w;
y = p2.x * p1.w - p1.x * p2.w;
w = p1.x * p2.y - p2.x * p1.y;
}
public double getX() throws NotRepresentableException {
double a = x / w;
if ((Double.isNaN(a)) || (Double.isInfinite(a))) {
throw new NotRepresentableException();
}
return a;
}
public double getY() throws NotRepresentableException {
double a = y / w;
if ((Double.isNaN(a)) || (Double.isInfinite(a))) {
throw new NotRepresentableException();
}
return a;
}
public Coordinate getCoordinate() throws NotRepresentableException {
Coordinate p = new Coordinate();
p.x = getX();
p.y = getY();
return p;
}
}