1 /*
2  * Copyright (c) 2016 Vivid Solutions.
3  *
4  * All rights reserved. This program and the accompanying materials
5  * are made available under the terms of the Eclipse Public License 2.0
6  * and Eclipse Distribution License v. 1.0 which accompanies this distribution.
7  * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
8  * and the Eclipse Distribution License is available at
9  *
10  * http://www.eclipse.org/org/documents/edl-v10.php.
11  */
12 package org.locationtech.jts.algorithm.distance;
13 
14 import org.locationtech.jts.geom.Coordinate;
15 import org.locationtech.jts.geom.Geometry;
16 import org.locationtech.jts.geom.GeometryCollection;
17 import org.locationtech.jts.geom.LineSegment;
18 import org.locationtech.jts.geom.LineString;
19 import org.locationtech.jts.geom.Polygon;
20 
21 /**
22  * Computes the Euclidean distance (L2 metric) from a {@link Coordinate} to a {@link Geometry}.
23  * Also computes two points on the geometry which are separated by the distance found.
24  */
25 public class DistanceToPoint
26 {
27 
DistanceToPoint()28   public DistanceToPoint() {
29   }
30 
computeDistance(Geometry geom, Coordinate pt, PointPairDistance ptDist)31   public static void computeDistance(Geometry geom, Coordinate pt, PointPairDistance ptDist)
32   {
33     if (geom instanceof LineString) {
34       computeDistance((LineString) geom, pt, ptDist);
35     }
36     else if (geom instanceof Polygon) {
37       computeDistance((Polygon) geom, pt, ptDist);
38     }
39     else if (geom instanceof GeometryCollection) {
40       GeometryCollection gc = (GeometryCollection) geom;
41       for (int i = 0; i < gc.getNumGeometries(); i++) {
42         Geometry g = gc.getGeometryN(i);
43         computeDistance(g, pt, ptDist);
44       }
45     }
46     else { // assume geom is Point
47       ptDist.setMinimum(geom.getCoordinate(), pt);
48     }
49   }
50 
computeDistance(LineString line, Coordinate pt, PointPairDistance ptDist)51   public static void computeDistance(LineString line, Coordinate pt, PointPairDistance ptDist)
52   {
53     LineSegment tempSegment = new LineSegment();
54     Coordinate[] coords = line.getCoordinates();
55     for (int i = 0; i < coords.length - 1; i++) {
56       tempSegment.setCoordinates(coords[i], coords[i + 1]);
57       // this is somewhat inefficient - could do better
58       Coordinate closestPt = tempSegment.closestPoint(pt);
59       ptDist.setMinimum(closestPt, pt);
60     }
61   }
62 
computeDistance(LineSegment segment, Coordinate pt, PointPairDistance ptDist)63   public static void computeDistance(LineSegment segment, Coordinate pt, PointPairDistance ptDist)
64   {
65     Coordinate closestPt = segment.closestPoint(pt);
66     ptDist.setMinimum(closestPt, pt);
67   }
68 
computeDistance(Polygon poly, Coordinate pt, PointPairDistance ptDist)69   public static void computeDistance(Polygon poly, Coordinate pt, PointPairDistance ptDist)
70   {
71     computeDistance(poly.getExteriorRing(), pt, ptDist);
72     for (int i = 0; i < poly.getNumInteriorRing(); i++) {
73       computeDistance(poly.getInteriorRingN(i), pt, ptDist);
74     }
75   }
76 }
77