get Intersection Points - Java java.lang

Java examples for java.lang:Math Geometry Line

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Description

get Intersection Points

Demo Code


//package com.java2s;

import java.awt.geom.Line2D;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;

public class Main {
    /**//from   w ww.j a v  a  2 s  .c  o m
     * @param line
     * @param rect
     * @return Point2D[0] = Top line; Point2D[1] = Bottom line; Point2D[3] = Left line; Point2D[4] = Right line;
     */
    public static Point2D[] getIntersectionPoints(final Line2D line,
            final Rectangle2D rect) {
        Point2D[] p = new Point2D[4];

        // Top line
        p[0] = getIntersectionPoint(line, new Line2D.Double(rect.getX(),
                rect.getY(), rect.getX() + rect.getWidth(), rect.getY()));
        // Bottom line
        p[1] = getIntersectionPoint(
                line,
                new Line2D.Double(rect.getX(), rect.getY()
                        + rect.getHeight(), rect.getX() + rect.getWidth(),
                        rect.getY() + rect.getHeight()));
        // Left side...
        p[2] = getIntersectionPoint(line, new Line2D.Double(rect.getX(),
                rect.getY(), rect.getX(), rect.getY() + rect.getHeight()));
        // Right side
        p[3] = getIntersectionPoint(
                line,
                new Line2D.Double(rect.getX() + rect.getWidth(), rect
                        .getY(), rect.getX() + rect.getWidth(), rect.getY()
                        + rect.getHeight()));

        return p;
    }

    /**
     * Computes the intersection between two lines. The calculated point is approximate, 
     * @param p1 Point 1 of Line 1
     * @param p2 Point 2 of Line 1
     * @param p3 Point 1 of Line 2
     * @param p4 Point 2 of Line 2
     * @return Point where the segments intersect, or null if they don't
     */
    public static Point2D getIntersectionPoint(final Point2D p1,
            final Point2D p2, final Point2D p3, final Point2D p4) {
        return getIntersectionPoint(new Line2D.Double(p1, p2),
                new Line2D.Double(p3, p4));
    }

    public static Point2D getIntersectionPoint(final Line2D lineA,
            final Line2D lineB) {
        double a1x = lineA.getX1();
        double a1y = lineA.getY1();
        double a2x = lineA.getX2();
        double a2y = lineA.getY2();

        double b1x = lineB.getX1();
        double b1y = lineB.getY1();
        double b2x = lineB.getX2();
        double b2y = lineB.getY2();

        Point2D p = null;
        double d = (b2y - b1y) * (a2x - a1x) - (b2x - b1x) * (a2y - a1y);

        if (d != 0) {
            double ua = ((b2x - b1x) * (a1y - b1y) - (b2y - b1y)
                    * (a1x - b1x))
                    / d;
            double ub = ((a2x - a1x) * (a1y - b1y) - (a2y - a1y)
                    * (a1x - b1x))
                    / d;

            if (0 <= ua && ua <= 1 && 0 <= ub && ub <= 1) {
                double xi = a1x + ua * (a2x - a1x);
                double yi = a1y + ua * (a2y - a1y);
                p = new Point2D.Double(xi, yi);
            }
        }

        return p;
    }
}

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