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PlantUML is a component that allows to quickly write : * sequence diagram, * use case diagram, * class diagram, * activity diagram, * component diagram, * state diagram * object diagram

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/* ========================================================================
 * PlantUML : a free UML diagram generator
 * ========================================================================
 *
 * (C) Copyright 2009-2013, Arnaud Roques
 *
 * Project Info:  http://plantuml.sourceforge.net
 * 
 * This file is part of PlantUML.
 *
 * PlantUML is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * PlantUML 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 General Public
 * License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
 * USA.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
 * in the United States and other countries.]
 *
 * Original Author:  Arnaud Roques
 *
 * Revision $Revision: 4236 $
 * 
 */
package net.sourceforge.plantuml.posimo;

import java.awt.geom.Line2D;
import java.awt.geom.Point2D;

public class LineSegmentIntersection {

	private final Point2D inter;
	
	// http://local.wasp.uwa.edu.au/~pbourke/geometry/lineline2d/

	public LineSegmentIntersection(Line2D segment, Line2D lineB) {
		final double x1 = segment.getX1();
		final double y1 = segment.getY1();
		final double x2 = segment.getX2();
		final double y2 = segment.getY2();
		final double x3 = lineB.getX1();
		final double y3 = lineB.getY1();
		final double x4 = lineB.getX2();
		final double y4 = lineB.getY2();

		final double den = (y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1);

		if (den == 0) {
			inter = null;
		} else {

			final double uA1 = (x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3);
			final double uA = uA1 / den;

			final double x = x1 + uA * (x2 - x1);
			final double y = y1 + uA * (y2 - y1);

			if (uA >= 0 && uA <= 1) {
				inter = new Point2D.Double(x, y);
			} else {
				inter = null;
			}
		}
	}

	public final Point2D getIntersection() {
		return inter;
	}

}