Class SimpleGeometryPrecisionReducer

1
2	/*
3	* Copyright (c) 2016 Vivid Solutions.
4	*
5	* All rights reserved. This program and the accompanying materials
6	* are made available under the terms of the Eclipse Public License 2.0
7	* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
8	* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
9	* and the Eclipse Distribution License is available at
10	*
11	* http://www.eclipse.org/org/documents/edl-v10.php.
12	*/
13	package org.locationtech.jts.precision;
14
15	import org.locationtech.jts.geom.Coordinate;
16	import org.locationtech.jts.geom.CoordinateList;
17	import org.locationtech.jts.geom.Geometry;
18	import org.locationtech.jts.geom.GeometryFactory;
19	import org.locationtech.jts.geom.LineString;
20	import org.locationtech.jts.geom.LinearRing;
21	import org.locationtech.jts.geom.Polygonal;
22	import org.locationtech.jts.geom.PrecisionModel;
23	import org.locationtech.jts.geom.util.GeometryEditor;
24
25	/**
26	* Reduces the precision of the coordinates of a {@link Geometry}
27	* according to the supplied {@link PrecisionModel}, without
28	* attempting to preserve valid topology.
29	* <p>
30	* In the case of {@link Polygonal} geometries,
31	* the topology of the resulting geometry may be invalid if
32	* topological collapse occurs due to coordinates being shifted.
33	* It is up to the client to check this and handle it if necessary.
34	* Collapses may not matter for some uses. An example
35	* is simplifying the input to the buffer algorithm.
36	* The buffer algorithm does not depend on the validity of the input geometry.
37	*
38	* @version 1.7
39	*
40	* @deprecated use GeometryPrecisionReducer
41	*/
42	public class SimpleGeometryPrecisionReducer
43	{
44	/**
45	* Convenience method for doing precision reduction on a single geometry,
46	* with collapses removed and keeping the geometry precision model the same.
47	*
48	* @param g
49	* @param precModel
50	* @return the reduced geometry
51	*/
52	public static Geometry reduce(Geometry g, PrecisionModel precModel)
53	{
54	SimpleGeometryPrecisionReducer reducer = new SimpleGeometryPrecisionReducer(precModel);
55	return reducer.reduce(g);
56	}
57
58	private PrecisionModel newPrecisionModel;
59	private boolean removeCollapsed = true;
60	private boolean changePrecisionModel = false;
61
62	public SimpleGeometryPrecisionReducer(PrecisionModel pm)
63	{
64	newPrecisionModel = pm;
65	}
66
67	/**
68	* Sets whether the reduction will result in collapsed components
69	* being removed completely, or simply being collapsed to an (invalid)
70	* Geometry of the same type.
71	* The default is to remove collapsed components.
72	*
73	* @param removeCollapsed if <code>true</code> collapsed components will be removed
74	*/
75	public void setRemoveCollapsedComponents(boolean removeCollapsed)
76	{
77	this.removeCollapsed = removeCollapsed;
78	}
79
80	/**
81	* Sets whether the {@link PrecisionModel} of the new reduced Geometry
82	* will be changed to be the {@link PrecisionModel} supplied to
83	* specify the precision reduction.
84	* <p>
85	* The default is to <b>not</b> change the precision model
86	*
87	* @param changePrecisionModel if <code>true</code> the precision model of the created Geometry will be the
88	* the precisionModel supplied in the constructor.
89	*/
90	public void setChangePrecisionModel(boolean changePrecisionModel)
91	{
92	this.changePrecisionModel = changePrecisionModel;
93	}
94
95	public Geometry reduce(Geometry geom)
96	{
97	GeometryEditor geomEdit;
98	if (changePrecisionModel) {
99	GeometryFactory newFactory = new GeometryFactory(newPrecisionModel, geom.getFactory().getSRID());
100	geomEdit = new GeometryEditor(newFactory);
101	}
102	else
103	// don't change geometry factory
104	geomEdit = new GeometryEditor();
105
106	return geomEdit.edit(geom, new PrecisionReducerCoordinateOperation());
107	}
108
109	private class PrecisionReducerCoordinateOperation
110	extends GeometryEditor.CoordinateOperation
111	{
112	public Coordinate[] edit(Coordinate[] coordinates, Geometry geom)
113	{
114	if (coordinates.length == 0) return null;
115
116	Coordinate[] reducedCoords = new Coordinate[coordinates.length];
117	// copy coordinates and reduce
118	for (int i = 0; i < coordinates.length; i++) {
119	Coordinate coord = new Coordinate(coordinates[i]);
120	newPrecisionModel.makePrecise(coord);
121	reducedCoords[i] = coord;
122	}
123	// remove repeated points, to simplify returned geometry as much as possible
124	CoordinateList noRepeatedCoordList = new CoordinateList(reducedCoords, false);
125	Coordinate[] noRepeatedCoords = noRepeatedCoordList.toCoordinateArray();
126
127	/**
128	* Check to see if the removal of repeated points
129	* collapsed the coordinate List to an invalid length
130	* for the type of the parent geometry.
131	* It is not necessary to check for Point collapses, since the coordinate list can
132	* never collapse to less than one point.
133	* If the length is invalid, return the full-length coordinate array
134	* first computed, or null if collapses are being removed.
135	* (This may create an invalid geometry - the client must handle this.)
136	*/
137	int minLength = 0;
138	if (geom instanceof LineString) minLength = 2;
139	if (geom instanceof LinearRing) minLength = 4;
140
141	Coordinate[] collapsedCoords = reducedCoords;
142	if (removeCollapsed) collapsedCoords = null;
143
144	// return null or orignal length coordinate array
145	if (noRepeatedCoords.length < minLength) {
146	return collapsedCoords;
147	}
148
149	// ok to return shorter coordinate array
150	return noRepeatedCoords;
151	}
152	}
153	}
154