Java Distance Calculate distance(int px, int py, int x1, int y1, int x2, int y2)

Description

Calculates the distance between a point and a line segment.

License

Open Source License

Parameter

Parameter	Description
px	x-coordinate of the point
py	y-coordinate of the point
x1	x-coordinate of segment point 1
y1	y-coordinate of segment point 1
x2	x-coordinate of segment point 2
y2	y-coordinate of segment point 2

Return

the distance in pixels

Declaration

public static double distance(int px, int py, int x1, int y1, int x2, int y2) 

Method Source Code

//package com.java2s;
/*****************************************************************************
 * Copyright (c) 2007, 2014 Intel Corporation, Ericsson
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:// w  w  w.j ava 2 s .  com
 *     Intel Corporation - Initial API and implementation
 *     Ruslan A. Scherbakov, Intel - Initial API and implementation
 *     Alvaro Sanchez-Leon - Udpated for TMF
 *     Patrick Tasse - Refactoring
 *     Marc-Andre Laperle - Add time zone preference
 *****************************************************************************/

public class Main {
    /**
     * Calculates the distance between a point and a line segment. If the point
     * is in the perpendicular region between the segment points, return the
     * distance from the point to its projection on the segment. Otherwise
     * return the distance from the point to its closest segment point.
     *
     * @param px
     *            x-coordinate of the point
     * @param py
     *            y-coordinate of the point
     * @param x1
     *            x-coordinate of segment point 1
     * @param y1
     *            y-coordinate of segment point 1
     * @param x2
     *            x-coordinate of segment point 2
     * @param y2
     *            y-coordinate of segment point 2
     *
     * @return the distance in pixels
     */
    public static double distance(int px, int py, int x1, int y1, int x2, int y2) {
        double length2 = distance2(x1, y1, x2, y2);
        if (length2 == 0) {
            return Math.sqrt(distance2(px, py, x1, y1));
        }
        // 'r' is the ratio of the position, between segment point 1 and segment
        // point 2, of the projection of the point on the segment
        double r = ((px - x1) * (x2 - x1) + (py - y1) * (y2 - y1)) / length2;
        if (r <= 0.0) {
            // the projection is before segment point 1, return distance from
            // the point to segment point 1
            return Math.sqrt(distance2(px, py, x1, y1));
        }
        if (r >= 1.0) {
            // the projection is after segment point 2, return distance from
            // the point to segment point 2
            return Math.sqrt(distance2(px, py, x2, y2));
        }
        // the projection is between the segment points, return distance from
        // the point to its projection on the segment
        int x = (int) (x1 + r * (x2 - x1));
        int y = (int) (y1 + r * (y2 - y1));
        return Math.sqrt(distance2(px, py, x, y));
    }

    /**
     * Calculates the square of the distance between two points.
     *
     * @param x1
     *            x-coordinate of point 1
     * @param y1
     *            y-coordinate of point 1
     * @param x2
     *            x-coordinate of point 2
     * @param y2
     *            y-coordinate of point 2
     *
     * @return the square of the distance in pixels^2
     */
    public static double distance2(int x1, int y1, int x2, int y2) {
        int dx = x2 - x1;
        int dy = y2 - y1;
        int d2 = dx * dx + dy * dy;
        return d2;
    }
}

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