Java Geometry Algorithm colinearPoint(Line2D line, Point2D point, double distance)

Description

colinear Point

License

Open Source License

Declaration

public static Point2D colinearPoint(Line2D line, Point2D point, double distance) 

Method Source Code

//package com.java2s;
/*//from   w w  w .j av  a  2 s.c om
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 * 
 *    (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.
 */

import java.awt.geom.Line2D;

import java.awt.geom.Point2D;

import static java.lang.Math.*;

public class Main {

    public static Point2D colinearPoint(Line2D line, Point2D point, double distance) {
        return colinearPoint(line.getX1(), line.getY1(), line.getX2(), line.getY2(), point.getX(), point.getY(),
                distance);
    }

    public static Point2D colinearPoint(double x1, double y1, double x2, double y2, double x, double y,
            double distance) {
        final double ox1 = x1;
        final double oy1 = y1;
        final double ox2 = x2;
        final double oy2 = y2;
        distance *= distance;
        if (x1 == x2) {
            double dy = x1 - x;
            dy = sqrt(distance - dy * dy);
            y1 = y - dy;
            y2 = y + dy;
        } else if (y1 == y2) {
            double dx = y1 - y;
            dx = sqrt(distance - dx * dx);
            x1 = x - dx;
            x2 = x + dx;
        } else {
            final double m = (y1 - y2) / (x2 - x1);
            final double y0 = (y2 - y) + m * (x2 - x);
            final double B = m * y0;
            final double A = m * m + 1;
            final double C = sqrt(B * B + A * (distance - y0 * y0));
            x1 = (B + C) / A;
            x2 = (B - C) / A;
            y1 = y + y0 - m * x1;
            y2 = y + y0 - m * x2;
            x1 += x;
            x2 += x;
        }
        boolean in1, in2;
        if (oy1 > oy2) {
            in1 = y1 <= oy1 && y1 >= oy2;
            in2 = y2 <= oy1 && y2 >= oy2;
        } else {
            in1 = y1 >= oy1 && y1 <= oy2;
            in2 = y2 >= oy1 && y2 <= oy2;
        }
        if (ox1 > ox2) {
            in1 &= x1 <= ox1 && x1 >= ox2;
            in2 &= x2 <= ox1 && x2 >= ox2;
        } else {
            in1 &= x1 >= ox1 && x1 <= ox2;
            in2 &= x2 >= ox1 && x2 <= ox2;
        }
        if (!in1 && !in2)
            return null;
        if (!in1)
            return new Point2D.Double(x2, y2);
        if (!in2)
            return new Point2D.Double(x1, y1);
        x = x1 - ox1;
        y = y1 - oy1;
        final double d1 = x * x + y * y;
        x = x2 - ox1;
        y = y2 - oy1;
        final double d2 = x * x + y * y;
        if (d1 > d2)
            return new Point2D.Double(x2, y2);
        else
            return new Point2D.Double(x1, y1);
    }
}

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