Class GeometryNoder

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.noding.snapround;
14
15	import java.util.ArrayList;
16	import java.util.Collection;
17	import java.util.Iterator;
18	import java.util.List;
19
20	import org.locationtech.jts.geom.Geometry;
21	import org.locationtech.jts.geom.GeometryFactory;
22	import org.locationtech.jts.geom.LineString;
23	import org.locationtech.jts.geom.PrecisionModel;
24	import org.locationtech.jts.geom.util.LinearComponentExtracter;
25	import org.locationtech.jts.noding.NodedSegmentString;
26	import org.locationtech.jts.noding.Noder;
27	import org.locationtech.jts.noding.NodingValidator;
28	import org.locationtech.jts.noding.SegmentString;
29
30	/**
31	* Nodes the linework in a list of {@link Geometry}s using Snap-Rounding
32	* to a given {@link PrecisionModel}.
33	* <p>
34	* The input coordinates are expected to be rounded
35	* to the given precision model.
36	* This class does not perform that function.
37	* <code>GeometryPrecisionReducer</code> may be used to do this.
38	* <p>
39	* This class does <b>not</b> dissolve the output linework,
40	* so there may be duplicate linestrings in the output.
41	* Subsequent processing (e.g. polygonization) may require
42	* the linework to be unique. Using <code>UnaryUnion</code> is one way
43	* to do this (although this is an inefficient approach).
44	*
45	*
46	*/
47	public class GeometryNoder
48	{
49	private GeometryFactory geomFact;
50	private PrecisionModel pm;
51	private boolean isValidityChecked = false;
52
53	/**
54	* Creates a new noder which snap-rounds to a grid specified
55	* by the given {@link PrecisionModel}.
56	*
57	* @param pm the precision model for the grid to snap-round to
58	*/
59	public GeometryNoder(PrecisionModel pm) {
60	this.pm = pm;
61	}
62
63	/**
64	* Sets whether noding validity is checked after noding is performed.
65	*
66	* @param isValidityChecked
67	*/
68	public void setValidate(boolean isValidityChecked)
69	{
70	this.isValidityChecked = isValidityChecked;
71	}
72
73	/**
74	* Nodes the linework of a set of Geometrys using SnapRounding.
75	*
76	* @param geoms a Collection of Geometrys of any type
77	* @return a List of LineStrings representing the noded linework of the input
78	*/
79	public List node(Collection geoms)
80	{
81	// get geometry factory
82	Geometry geom0 = (Geometry) geoms.iterator().next();
83	geomFact = geom0.getFactory();
84
85	List segStrings = toSegmentStrings(extractLines(geoms));
86	//Noder sr = new SimpleSnapRounder(pm);
87	Noder sr = new MCIndexSnapRounder(pm);
88	sr.computeNodes(segStrings);
89	Collection nodedLines = sr.getNodedSubstrings();
90
91	//TODO: improve this to check for full snap-rounded correctness
92	if (isValidityChecked) {
93	NodingValidator nv = new NodingValidator(nodedLines);
94	nv.checkValid();
95	}
96
97	return toLineStrings(nodedLines);
98	}
99
100	private List toLineStrings(Collection segStrings)
101	{
102	List lines = new ArrayList();
103	for (Iterator it = segStrings.iterator(); it.hasNext(); ) {
104	SegmentString ss = (SegmentString) it.next();
105	// skip collapsed lines
106	if (ss.size() < 2)
107	continue;
108	lines.add(geomFact.createLineString(ss.getCoordinates()));
109	}
110	return lines;
111	}
112
113	private List extractLines(Collection geoms)
114	{
115	List lines = new ArrayList();
116	LinearComponentExtracter lce = new LinearComponentExtracter(lines);
117	for (Iterator it = geoms.iterator(); it.hasNext(); ) {
118	Geometry geom = (Geometry) it.next();
119	geom.apply(lce);
120	}
121	return lines;
122	}
123
124	private List toSegmentStrings(Collection lines)
125	{
126	List segStrings = new ArrayList();
127	for (Iterator it = lines.iterator(); it.hasNext(); ) {
128	LineString line = (LineString) it.next();
129	segStrings.add(new NodedSegmentString(line.getCoordinates(), null));
130	}
131	return segStrings;
132	}
133	}
134