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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.math3.geometry.euclidean.twod;
import org.apache.commons.math3.geometry.Point;
import org.apache.commons.math3.util.FastMath;
/** Simple container for a two-points segment.
* @since 3.0
*/
public class Segment {
/** Start point of the segment. */
private final Vector2D start;
/** End point of the segment. */
private final Vector2D end;
/** Line containing the segment. */
private final Line line;
/** Build a segment.
* @param start start point of the segment
* @param end end point of the segment
* @param line line containing the segment
*/
public Segment(final Vector2D start, final Vector2D end, final Line line) {
this.start = start;
this.end = end;
this.line = line;
}
/** Get the start point of the segment.
* @return start point of the segment
*/
public Vector2D getStart() {
return start;
}
/** Get the end point of the segment.
* @return end point of the segment
*/
public Vector2D getEnd() {
return end;
}
/** Get the line containing the segment.
* @return line containing the segment
*/
public Line getLine() {
return line;
}
/** Calculates the shortest distance from a point to this line segment.
* <p>
* If the perpendicular extension from the point to the line does not
* cross in the bounds of the line segment, the shortest distance to
* the two end points will be returned.
* </p>
*
* Algorithm adapted from:
* <a href="http://www.codeguru.com/forum/printthread.php?s=cc8cf0596231f9a7dba4da6e77c29db3&t=194400&pp=15&page=1">
* Thread @ Codeguru</a>
*
* @param p to check
* @return distance between the instance and the point
* @since 3.1
*/
public double distance(final Vector2D p) {
final double deltaX = end.getX() - start.getX();
final double deltaY = end.getY() - start.getY();
final double r = ((p.getX() - start.getX()) * deltaX + (p.getY() - start.getY()) * deltaY) /
(deltaX * deltaX + deltaY * deltaY);
// r == 0 => P = startPt
// r == 1 => P = endPt
// r < 0 => P is on the backward extension of the segment
// r > 1 => P is on the forward extension of the segment
// 0 < r < 1 => P is on the segment
// if point isn't on the line segment, just return the shortest distance to the end points
if (r < 0 || r > 1) {
final double dist1 = getStart().distance((Point<Euclidean2D>) p);
final double dist2 = getEnd().distance((Point<Euclidean2D>) p);
return FastMath.min(dist1, dist2);
}
else {
// find point on line and see if it is in the line segment
final double px = start.getX() + r * deltaX;
final double py = start.getY() + r * deltaY;
final Vector2D interPt = new Vector2D(px, py);
return interPt.distance((Point<Euclidean2D>) p);
}
}
}
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