Class PointBuilder

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.overlay;
13
14	import java.util.ArrayList;
15	import java.util.Iterator;
16	import java.util.List;
17
18	import org.locationtech.jts.algorithm.PointLocator;
19	import org.locationtech.jts.geom.Coordinate;
20	import org.locationtech.jts.geom.GeometryFactory;
21	import org.locationtech.jts.geom.Point;
22	import org.locationtech.jts.geomgraph.Label;
23	import org.locationtech.jts.geomgraph.Node;
24
25	/**
26	* Constructs {@link Point}s from the nodes of an overlay graph.
27	* @version 1.7
28	*/
29	public class PointBuilder {
30	private OverlayOp op;
31	private GeometryFactory geometryFactory;
32	private List resultPointList = new ArrayList();
33
34	public PointBuilder(OverlayOp op, GeometryFactory geometryFactory, PointLocator ptLocator) {
35	this.op = op;
36	this.geometryFactory = geometryFactory;
37	// ptLocator is never used in this class
38	}
39
40	/**
41	* Computes the Point geometries which will appear in the result,
42	* given the specified overlay operation.
43	*
44	* @return a list of the Points objects in the result
45	*/
46	public List build(int opCode)
47	{
48	extractNonCoveredResultNodes(opCode);
49	/**
50	* It can happen that connected result nodes are still covered by
51	* result geometries, so must perform this filter.
52	* (For instance, this can happen during topology collapse).
53	*/
54	return resultPointList;
55	}
56
57	/**
58	* Determines nodes which are in the result, and creates {@link Point}s for them.
59	*
60	* This method determines nodes which are candidates for the result via their
61	* labelling and their graph topology.
62	*
63	* @param opCode the overlay operation
64	*/
65	private void extractNonCoveredResultNodes(int opCode)
66	{
67	// testing only
68	//if (true) return resultNodeList;
69
70	for (Iterator nodeit = op.getGraph().getNodes().iterator(); nodeit.hasNext(); ) {
71	Node n = (Node) nodeit.next();
72
73	// filter out nodes which are known to be in the result
74	if (n.isInResult())
75	continue;
76	// if an incident edge is in the result, then the node coordinate is included already
77	if (n.isIncidentEdgeInResult())
78	continue;
79	if (n.getEdges().getDegree() == 0 \|\| opCode == OverlayOp.INTERSECTION) {
80
81	/**
82	* For nodes on edges, only INTERSECTION can result in edge nodes being included even
83	* if none of their incident edges are included
84	*/
85	Label label = n.getLabel();
86	if (OverlayOp.isResultOfOp(label, opCode)) {
87	filterCoveredNodeToPoint(n);
88	}
89	}
90	}
91	//System.out.println("connectedResultNodes collected = " + connectedResultNodes.size());
92	}
93
94	/**
95	* Converts non-covered nodes to Point objects and adds them to the result.
96	*
97	* A node is covered if it is contained in another element Geometry
98	* with higher dimension (e.g. a node point might be contained in a polygon,
99	* in which case the point can be eliminated from the result).
100	*
101	* @param n the node to test
102	*/
103	private void filterCoveredNodeToPoint(Node n)
104	{
105	Coordinate coord = n.getCoordinate();
106	if (! op.isCoveredByLA(coord)) {
107	Point pt = geometryFactory.createPoint(coord);
108	resultPointList.add(pt);
109	}
110	}
111	}
112