Class BufferCurveMaximumDistanceFinder

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.operation.buffer.validate;
13
14	import org.locationtech.jts.geom.Coordinate;
15	import org.locationtech.jts.geom.CoordinateFilter;
16	import org.locationtech.jts.geom.CoordinateSequence;
17	import org.locationtech.jts.geom.CoordinateSequenceFilter;
18	import org.locationtech.jts.geom.Geometry;
19
20	/**
21	* Finds the approximate maximum distance from a buffer curve to
22	* the originating geometry.
23	* This is similar to the Discrete Oriented Hausdorff distance
24	* from the buffer curve to the input.
25	* <p>
26	* The approximate maximum distance is determined by testing
27	* all vertices in the buffer curve, as well
28	* as midpoints of the curve segments.
29	* Due to the way buffer curves are constructed, this
30	* should be a very close approximation.
31	*
32	* @author mbdavis
33	*
34	*/
35	public class BufferCurveMaximumDistanceFinder
36	{
37	private Geometry inputGeom;
38	private PointPairDistance maxPtDist = new PointPairDistance();
39
40	public BufferCurveMaximumDistanceFinder(Geometry inputGeom)
41	{
42	this.inputGeom = inputGeom;
43	}
44
45	public double findDistance(Geometry bufferCurve)
46	{
47	computeMaxVertexDistance(bufferCurve);
48	computeMaxMidpointDistance(bufferCurve);
49	return maxPtDist.getDistance();
50	}
51
52	public PointPairDistance getDistancePoints()
53	{
54	return maxPtDist;
55	}
56	private void computeMaxVertexDistance(Geometry curve)
57	{
58	MaxPointDistanceFilter distFilter = new MaxPointDistanceFilter(inputGeom);
59	curve.apply(distFilter);
60	maxPtDist.setMaximum(distFilter.getMaxPointDistance());
61	}
62
63	private void computeMaxMidpointDistance(Geometry curve)
64	{
65	MaxMidpointDistanceFilter distFilter = new MaxMidpointDistanceFilter(inputGeom);
66	curve.apply(distFilter);
67	maxPtDist.setMaximum(distFilter.getMaxPointDistance());
68	}
69
70	public static class MaxPointDistanceFilter implements CoordinateFilter {
71	private PointPairDistance maxPtDist = new PointPairDistance();
72	private PointPairDistance minPtDist = new PointPairDistance();
73	private Geometry geom;
74
75	public MaxPointDistanceFilter(Geometry geom) {
76	this.geom = geom;
77	}
78
79	public void filter(Coordinate pt) {
80	minPtDist.initialize();
81	DistanceToPointFinder.computeDistance(geom, pt, minPtDist);
82	maxPtDist.setMaximum(minPtDist);
83	}
84
85	public PointPairDistance getMaxPointDistance() {
86	return maxPtDist;
87	}
88	}
89
90	public static class MaxMidpointDistanceFilter
91	implements CoordinateSequenceFilter
92	{
93	private PointPairDistance maxPtDist = new PointPairDistance();
94	private PointPairDistance minPtDist = new PointPairDistance();
95	private Geometry geom;
96
97	public MaxMidpointDistanceFilter(Geometry geom) {
98	this.geom = geom;
99	}
100
101	public void filter(CoordinateSequence seq, int index)
102	{
103	if (index == 0)
104	return;
105
106	Coordinate p0 = seq.getCoordinate(index - 1);
107	Coordinate p1 = seq.getCoordinate(index);
108	Coordinate midPt = new Coordinate(
109	(p0.x + p1.x)/2,
110	(p0.y + p1.y)/2);
111
112	minPtDist.initialize();
113	DistanceToPointFinder.computeDistance(geom, midPt, minPtDist);
114	maxPtDist.setMaximum(minPtDist);
115	}
116
117	public boolean isGeometryChanged() { return false; }
118
119	public boolean isDone() { return false; }
120
121	public PointPairDistance getMaxPointDistance() {
122	return maxPtDist;
123	}
124	}
125
126	}
127