Class HausdorffSimilarityMeasure

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
13	package org.locationtech.jts.algorithm.match;
14
15	import org.locationtech.jts.algorithm.distance.DiscreteHausdorffDistance;
16	import org.locationtech.jts.geom.Envelope;
17	import org.locationtech.jts.geom.Geometry;
18
19	/**
20	* Measures the degree of similarity between two {@link Geometry}s
21	* using the Hausdorff distance metric.
22	* The measure is normalized to lie in the range [0, 1].
23	* Higher measures indicate a great degree of similarity.
24	* <p>
25	* The measure is computed by computing the Hausdorff distance
26	* between the input geometries, and then normalizing
27	* this by dividing it by the diagonal distance across
28	* the envelope of the combined geometries.
29	*
30	* @author mbdavis
31	*
32	*/
33	public class HausdorffSimilarityMeasure
34	implements SimilarityMeasure
35	{
36	/*
37	public static double measure(Geometry a, Geometry b)
38	{
39	HausdorffSimilarityMeasure gv = new HausdorffSimilarityMeasure(a, b);
40	return gv.measure();
41	}
42	*/
43
44	public HausdorffSimilarityMeasure()
45	{
46	}
47
48	/*
49	* Densify a small amount to increase accuracy of Hausdorff distance
50	*/
51	private static final double DENSIFY_FRACTION = 0.25;
52
53	public double measure(Geometry g1, Geometry g2)
54	{
55	double distance = DiscreteHausdorffDistance.distance(g1, g2, DENSIFY_FRACTION);
56
57	Envelope env = new Envelope(g1.getEnvelopeInternal());
58	env.expandToInclude(g2.getEnvelopeInternal());
59	double envSize = diagonalSize(env);
60	// normalize so that more similarity produces a measure closer to 1
61	double measure = 1 - distance / envSize;
62
63	//System.out.println("Hausdorff distance = " + distance + ", measure = " + measure);
64	return measure;
65	}
66
67	public static double diagonalSize(Envelope env)
68	{
69	if (env.isNull()) return 0.0;
70
71	double width = env.getWidth();
72	double hgt = env.getHeight();
73	return Math.sqrt(width * width + hgt * hgt);
74	}
75	}
76