Class InputExtracter

1	/*
2	* Copyright (c) 2019 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	package org.locationtech.jts.operation.union;
13
14	import java.util.ArrayList;
15	import java.util.Collection;
16	import java.util.List;
17
18	import org.locationtech.jts.geom.Dimension;
19	import org.locationtech.jts.geom.Geometry;
20	import org.locationtech.jts.geom.GeometryCollection;
21	import org.locationtech.jts.geom.GeometryFactory;
22	import org.locationtech.jts.geom.GeometryFilter;
23	import org.locationtech.jts.geom.LineString;
24	import org.locationtech.jts.geom.Point;
25	import org.locationtech.jts.geom.Polygon;
26	import org.locationtech.jts.util.Assert;
27
28
29	/**
30	* Extracts atomic elements from
31	* input geometries or collections,
32	* recording the dimension found.
33	* Empty geometries are discarded since they
34	* do not contribute to the result of {@link UnaryUnionOp}.
35	*
36	* @author Martin Davis
37	*
38	*/
39	class InputExtracter implements GeometryFilter
40	{
41	/**
42	* Extracts elements from a collection of geometries.
43	*
44	* @param geoms a collection of geometries
45	* @return an extracter over the geometries
46	*/
47	public static InputExtracter extract(Collection<Geometry> geoms) {
48	InputExtracter extracter = new InputExtracter();
49	extracter.add(geoms);
50	return extracter;
51	}
52
53	/**
54	* Extracts elements from a geometry.
55	*
56	* @param geoms a geometry to extract from
57	* @return an extracter over the geometry
58	*/
59	public static InputExtracter extract(Geometry geom) {
60	InputExtracter extracter = new InputExtracter();
61	extracter.add(geom);
62	return extracter;
63	}
64
65	private GeometryFactory geomFactory = null;
66	private List<Polygon> polygons = new ArrayList<Polygon>();
67	private List<LineString> lines = new ArrayList<LineString>();
68	private List<Point> points = new ArrayList<Point>();
69
70	/**
71	* The default dimension for an empty GeometryCollection
72	*/
73	private int dimension = Dimension.FALSE;
74
75	public InputExtracter() {
76
77	}
78
79	/**
80	* Tests whether there were any non-empty geometries extracted.
81	*
82	* @return true if there is a non-empty geometry present
83	*/
84	public boolean isEmpty() {
85	return polygons.isEmpty()
86	&& lines.isEmpty()
87	&& points.isEmpty();
88	}
89
90	/**
91	* Gets the maximum dimension extracted.
92	*
93	* @return the maximum extracted dimension
94	*/
95	public int getDimension() {
96	return dimension;
97	}
98
99	/**
100	* Gets the geometry factory from the extracted geometry,
101	* if there is one.
102	* If an empty collection was extracted, will return <code>null</code>.
103	*
104	* @return a geometry factory, or null if one could not be determined
105	*/
106	public GeometryFactory getFactory() {
107	return geomFactory;
108	}
109
110	/**
111	* Gets the extracted atomic geometries of the given dimension <code>dim</code>.
112	*
113	* @param dim the dimension of geometry to return
114	* @return a list of the extracted geometries of dimension dim.
115	*/
116	public List getExtract(int dim) {
117	switch (dim) {
118	case 0: return points;
119	case 1: return lines;
120	case 2: return polygons;
121	}
122	Assert.shouldNeverReachHere("Invalid dimension: " + dim);
123	return null;
124	}
125
126	private void add(Collection<Geometry> geoms) {
127	for (Geometry geom : geoms) {
128	add(geom);
129	}
130	}
131
132	private void add(Geometry geom) {
133	if (geomFactory == null)
134	geomFactory = geom.getFactory();
135
136	geom.apply(this);
137	}
138
139	@Override
140	public void filter(Geometry geom) {
141	recordDimension( geom.getDimension() );
142
143	if (geom instanceof GeometryCollection) {
144	return;
145	}
146	/**
147	* Don't keep empty geometries
148	*/
149	if (geom.isEmpty())
150	return;
151
152	if (geom instanceof Polygon) {
153	polygons.add((Polygon) geom);
154	return;
155	}
156	else if (geom instanceof LineString) {
157	lines.add((LineString) geom);
158	return;
159	}
160	else if (geom instanceof Point) {
161	points.add((Point) geom);
162	return;
163	}
164	Assert.shouldNeverReachHere("Unhandled geometry type: " + geom.getGeometryType());
165	}
166
167	private void recordDimension(int dim) {
168	if (dim > dimension )
169	dimension = dim;
170	}
171	}
172