Java Line Intersect intersection(Line2D a, Line2D b)

Description

Computes the intersection between two lines.

License

LGPL

Parameter

Parameter	Description
x1	Point 1 of Line 1
y1	Point 1 of Line 1
x2	Point 2 of Line 1
y2	Point 2 of Line 1
x3	Point 1 of Line 2
y3	Point 1 of Line 2
x4	Point 2 of Line 2
y4	Point 2 of Line 2

Return

Point where the segments intersect, or null if they don't

Declaration

public static Point2D intersection(Line2D a, Line2D b) 

Method Source Code

//package com.java2s;
/**//from  w w  w .ja va2s .c  om
 * Computes the intersection between two lines. The calculated point is approximate, 
 * since integers are used. If you need a more precise result, use doubles
 * everywhere. 
 * (c) 2007 Alexander Hristov. Use Freely (LGPL license). http://www.ahristov.com
 *
 * @param x1 Point 1 of Line 1
 * @param y1 Point 1 of Line 1
 * @param x2 Point 2 of Line 1
 * @param y2 Point 2 of Line 1
 * @param x3 Point 1 of Line 2
 * @param y3 Point 1 of Line 2
 * @param x4 Point 2 of Line 2
 * @param y4 Point 2 of Line 2
 * @return Point where the segments intersect, or null if they don't
 */

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

public class Main {
    /**
     * Computes the intersection between two lines. The calculated point is approximate, 
     * since integers are used. If you need a more precise result, use doubles
     * everywhere. 
     * (c) 2007 Alexander Hristov. Use Freely (LGPL license). http://www.ahristov.com
     *
     * @param x1 Point 1 of Line 1
     * @param y1 Point 1 of Line 1
     * @param x2 Point 2 of Line 1
     * @param y2 Point 2 of Line 1
     * @param x3 Point 1 of Line 2
     * @param y3 Point 1 of Line 2
     * @param x4 Point 2 of Line 2
     * @param y4 Point 2 of Line 2
     * @return Point where the segments intersect, or null if they don't
     */
    public static Point2D intersection(Line2D a, Line2D b) {
        double x1 = a.getX1(), y1 = a.getY1(), x2 = a.getX2(), y2 = a.getY2(), x3 = b.getX1(), y3 = b.getY1(),
                x4 = b.getX2(), y4 = b.getY2();
        double d = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4);
        if (d == 0) {
            return null;
        }

        double xi = ((x3 - x4) * (x1 * y2 - y1 * x2) - (x1 - x2) * (x3 * y4 - y3 * x4)) / d;
        double yi = ((y3 - y4) * (x1 * y2 - y1 * x2) - (y1 - y2) * (x3 * y4 - y3 * x4)) / d;

        return new Point2D.Double(xi, yi);
    }
}

Related

1. intersect(int xa, int ya, int xb, int yb, int xc, int yc, int xd, int yd)
2. intersect(Point a, Point b, Point c, Point d)
3. intersect(Shape shape1, Shape shape2)
4. intersectClip(final Graphics2D g2d, final Shape clip)
5. intersection(Line2D lineA, Line2D lineB)
6. intersection(Point2D p1, Point2D p2, Point2D p3, Point2D p4)
7. intersectionPoint(final Line2D l1, final Line2D l2)
8. intersectionZJU(int x1, int y1, int x2, int y2, int x3, int y3, int x4, int y4)