Class FacetSequenceTreeBuilder

1	/*
2	* Copyright (c) 2016 Martin Davis.
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.operation.distance;
14
15	import java.util.ArrayList;
16	import java.util.Iterator;
17	import java.util.List;
18
19	import org.locationtech.jts.geom.CoordinateSequence;
20	import org.locationtech.jts.geom.Geometry;
21	import org.locationtech.jts.geom.GeometryComponentFilter;
22	import org.locationtech.jts.geom.LineString;
23	import org.locationtech.jts.geom.Point;
24	import org.locationtech.jts.index.strtree.STRtree;
25
26
27	public class FacetSequenceTreeBuilder {
28	// 6 seems to be a good facet sequence size
29	private static final int FACET_SEQUENCE_SIZE = 6;
30
31	// Seems to be better to use a minimum node capacity
32	private static final int STR_TREE_NODE_CAPACITY = 4;
33
34	public static STRtree build(Geometry g) {
35	STRtree tree = new STRtree(STR_TREE_NODE_CAPACITY);
36	List sections = computeFacetSequences(g);
37	for (Iterator i = sections.iterator(); i.hasNext();) {
38	FacetSequence section = (FacetSequence) i.next();
39	tree.insert(section.getEnvelope(), section);
40	}
41	tree.build();
42	return tree;
43	}
44
45	/**
46	* Creates facet sequences
47	*
48	* @param g
49	* @return List<GeometryFacetSequence>
50	*/
51	private static List computeFacetSequences(Geometry g) {
52	final List sections = new ArrayList();
53
54	g.apply(new GeometryComponentFilter() {
55
56	public void filter(Geometry geom) {
57	CoordinateSequence seq = null;
58	if (geom instanceof LineString) {
59	seq = ((LineString) geom).getCoordinateSequence();
60	addFacetSequences(geom, seq, sections);
61	}
62	else if (geom instanceof Point) {
63	seq = ((Point) geom).getCoordinateSequence();
64	addFacetSequences(geom, seq, sections);
65	}
66	}
67	});
68	return sections;
69	}
70
71	private static void addFacetSequences(Geometry geom, CoordinateSequence pts, List sections) {
72	int i = 0;
73	int size = pts.size();
74	while (i <= size - 1) {
75	int end = i + FACET_SEQUENCE_SIZE + 1;
76	// if only one point remains after this section, include it in this
77	// section
78	if (end >= size - 1)
79	end = size;
80	FacetSequence sect = new FacetSequence(geom, pts, i, end);
81	sections.add(sect);
82	i = i + FACET_SEQUENCE_SIZE;
83	}
84	}
85	}
86