Class InteriorPointLine

1
2	/*
3	* Copyright (c) 2016 Vivid Solutions.
4	*
5	* All rights reserved. This program and the accompanying materials
6	* are made available under the terms of the Eclipse Public License 2.0
7	* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
8	* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
9	* and the Eclipse Distribution License is available at
10	*
11	* http://www.eclipse.org/org/documents/edl-v10.php.
12	*/
13	package org.locationtech.jts.algorithm;
14
15	import org.locationtech.jts.geom.Coordinate;
16	import org.locationtech.jts.geom.Geometry;
17	import org.locationtech.jts.geom.GeometryCollection;
18	import org.locationtech.jts.geom.LineString;
19
20	/**
21	* Computes a point in the interior of an linear geometry.
22	* <h2>Algorithm</h2>
23	* <ul>
24	* <li>Find an interior vertex which is closest to
25	* the centroid of the linestring.
26	* <li>If there is no interior vertex, find the endpoint which is
27	* closest to the centroid.
28	* </ul>
29	*
30	* @version 1.7
31	*/
32	public class InteriorPointLine {
33
34	/**
35	* Computes an interior point for the
36	* linear components of a Geometry.
37	*
38	* @param geom the geometry to compute
39	* @return the computed interior point,
40	* or <code>null</code> if the geometry has no linear components
41	*/
42	public static Coordinate getInteriorPoint(Geometry geom) {
43	InteriorPointLine intPt = new InteriorPointLine(geom);
44	return intPt.getInteriorPoint();
45	}
46
47	private Coordinate centroid;
48	private double minDistance = Double.MAX_VALUE;
49
50	private Coordinate interiorPoint = null;
51
52	public InteriorPointLine(Geometry g)
53	{
54	centroid = g.getCentroid().getCoordinate();
55	addInterior(g);
56	if (interiorPoint == null)
57	addEndpoints(g);
58	}
59
60	public Coordinate getInteriorPoint()
61	{
62	return interiorPoint;
63	}
64
65	/**
66	* Tests the interior vertices (if any)
67	* defined by a linear Geometry for the best inside point.
68	* If a Geometry is not of dimension 1 it is not tested.
69	* @param geom the geometry to add
70	*/
71	private void addInterior(Geometry geom)
72	{
73	if (geom instanceof LineString) {
74	addInterior(geom.getCoordinates());
75	}
76	else if (geom instanceof GeometryCollection) {
77	GeometryCollection gc = (GeometryCollection) geom;
78	for (int i = 0; i < gc.getNumGeometries(); i++) {
79	addInterior(gc.getGeometryN(i));
80	}
81	}
82	}
83	private void addInterior(Coordinate[] pts)
84	{
85	for (int i = 1; i < pts.length - 1; i++) {
86	add(pts[i]);
87	}
88	}
89	/**
90	* Tests the endpoint vertices
91	* defined by a linear Geometry for the best inside point.
92	* If a Geometry is not of dimension 1 it is not tested.
93	* @param geom the geometry to add
94	*/
95	private void addEndpoints(Geometry geom)
96	{
97	if (geom instanceof LineString) {
98	addEndpoints(geom.getCoordinates());
99	}
100	else if (geom instanceof GeometryCollection) {
101	GeometryCollection gc = (GeometryCollection) geom;
102	for (int i = 0; i < gc.getNumGeometries(); i++) {
103	addEndpoints(gc.getGeometryN(i));
104	}
105	}
106	}
107	private void addEndpoints(Coordinate[] pts)
108	{
109	add(pts[0]);
110	add(pts[pts.length - 1]);
111	}
112
113	private void add(Coordinate point)
114	{
115	double dist = point.distance(centroid);
116	if (dist < minDistance) {
117	interiorPoint = new Coordinate(point);
118	minDistance = dist;
119	}
120	}
121
122	}
123