Class LineSegmentIndex

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.simplify;
14
15	import java.util.ArrayList;
16	import java.util.List;
17
18	import org.locationtech.jts.geom.Envelope;
19	import org.locationtech.jts.geom.LineSegment;
20	import org.locationtech.jts.index.ItemVisitor;
21	import org.locationtech.jts.index.quadtree.Quadtree;
22
23	/**
24	* An spatial index on a set of {@link LineSegment}s.
25	* Supports adding and removing items.
26	*
27	* @author Martin Davis
28	*/
29	class LineSegmentIndex
30	{
31	private Quadtree index = new Quadtree();
32
33	public LineSegmentIndex()
34	{
35	}
36
37	public void add(TaggedLineString line) {
38	TaggedLineSegment[] segs = line.getSegments();
39	for (int i = 0; i < segs.length; i++) {
40	TaggedLineSegment seg = segs[i];
41	add(seg);
42	}
43	}
44
45	public void add(LineSegment seg)
46	{
47	index.insert(new Envelope(seg.p0, seg.p1), seg);
48	}
49
50	public void remove(LineSegment seg)
51	{
52	index.remove(new Envelope(seg.p0, seg.p1), seg);
53	}
54
55	public List query(LineSegment querySeg)
56	{
57	Envelope env = new Envelope(querySeg.p0, querySeg.p1);
58
59	LineSegmentVisitor visitor = new LineSegmentVisitor(querySeg);
60	index.query(env, visitor);
61	List itemsFound = visitor.getItems();
62
63	// List listQueryItems = index.query(env);
64	// System.out.println("visitor size = " + itemsFound.size()
65	// + " query size = " + listQueryItems.size());
66	// List itemsFound = index.query(env);
67
68	return itemsFound;
69	}
70	}
71
72	/**
73	* ItemVisitor subclass to reduce volume of query results.
74	*/
75	class LineSegmentVisitor
76	implements ItemVisitor
77	{
78	// MD - only seems to make about a 10% difference in overall time.
79
80	private LineSegment querySeg;
81	private ArrayList items = new ArrayList();
82
83	public LineSegmentVisitor(LineSegment querySeg) {
84	this.querySeg = querySeg;
85	}
86
87	public void visitItem(Object item)
88	{
89	LineSegment seg = (LineSegment) item;
90	if (Envelope.intersects(seg.p0, seg.p1, querySeg.p0, querySeg.p1))
91	items.add(item);
92	}
93
94	public ArrayList getItems() { return items; }
95	}
96