/*
* Copyright (c) 2016 Vivid Solutions.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
*
* http://www.eclipse.org/org/documents/edl-v10.php.
*/
package org.locationtech.jts.triangulate;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import org.locationtech.jts.geom.Coordinate;
import org.locationtech.jts.geom.CoordinateArrays;
import org.locationtech.jts.geom.Envelope;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryCollection;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.geom.Polygon;
import org.locationtech.jts.triangulate.quadedge.QuadEdgeSubdivision;
/**
* A utility class which creates Voronoi Diagrams
* from collections of points.
* The diagram is returned as a {@link GeometryCollection} of {@link Polygon}s
* representing the faces of the Voronoi diagram.
* The faces are clipped to the larger of:
* <ul>
* <li> an envelope supplied by {@link #setClipEnvelope(Envelope)}
* <li> an envelope determined by the input sites
* </ul>
* The <tt>userData</tt> attribute of each face <tt>Polygon</tt> is set to
* the <tt>Coordinate</tt> of the corresponding input site.
* This allows using a <tt>Map</tt> to link faces to data associated with sites.
*
* @author Martin Davis
*
*/
public class VoronoiDiagramBuilder
{
private Collection siteCoords;
private double tolerance = 0.0;
private QuadEdgeSubdivision subdiv = null;
private Envelope clipEnv = null;
private Envelope diagramEnv = null;
/**
* Creates a new Voronoi diagram builder.
*
*/
public VoronoiDiagramBuilder()
{
}
/**
* Sets the sites (point or vertices) which will be diagrammed.
* All vertices of the given geometry will be used as sites.
*
* @param geom the geometry from which the sites will be extracted.
*/
public void setSites(Geometry geom)
{
// remove any duplicate points (they will cause the triangulation to fail)
siteCoords = DelaunayTriangulationBuilder.extractUniqueCoordinates(geom);
}
/**
* Sets the sites (point or vertices) which will be diagrammed
* from a collection of {@link Coordinate}s.
*
* @param coords a collection of Coordinates.
*/
public void setSites(Collection coords)
{
// remove any duplicate points (they will cause the triangulation to fail)
siteCoords = DelaunayTriangulationBuilder.unique(CoordinateArrays.toCoordinateArray(coords));
}
/**
* Sets the envelope to clip the diagram to.
* The diagram will be clipped to the larger
* of this envelope or an envelope surrounding the sites.
*
* @param clipEnv the clip envelope.
*/
public void setClipEnvelope(Envelope clipEnv)
{
this.clipEnv = clipEnv;
}
/**
* Sets the snapping tolerance which will be used
* to improved the robustness of the triangulation computation.
* A tolerance of 0.0 specifies that no snapping will take place.
*
* @param tolerance the tolerance distance to use
*/
public void setTolerance(double tolerance)
{
this.tolerance = tolerance;
}
private void create()
{
if (subdiv != null) return;
Envelope siteEnv = DelaunayTriangulationBuilder.envelope(siteCoords);
diagramEnv = siteEnv;
// add a buffer around the final envelope
double expandBy = Math.max(diagramEnv.getWidth(), diagramEnv.getHeight());
diagramEnv.expandBy(expandBy);
if (clipEnv != null)
diagramEnv.expandToInclude(clipEnv);
List vertices = DelaunayTriangulationBuilder.toVertices(siteCoords);
subdiv = new QuadEdgeSubdivision(siteEnv, tolerance);
IncrementalDelaunayTriangulator triangulator = new IncrementalDelaunayTriangulator(subdiv);
triangulator.insertSites(vertices);
}
/**
* Gets the {@link QuadEdgeSubdivision} which models the computed diagram.
*
* @return the subdivision containing the triangulation
*/
public QuadEdgeSubdivision getSubdivision()
{
create();
return subdiv;
}
/**
* Gets the faces of the computed diagram as a {@link GeometryCollection}
* of {@link Polygon}s, clipped as specified.
* <p>
* The <tt>userData</tt> attribute of each face <tt>Polygon</tt> is set to
* the <tt>Coordinate</tt> of the corresponding input site.
* This allows using a <tt>Map</tt> to link faces to data associated with sites.
*
* @param geomFact the geometry factory to use to create the output
* @return a <tt>GeometryCollection</tt> containing the face <tt>Polygon</tt>s of the diagram
*/
public Geometry getDiagram(GeometryFactory geomFact)
{
create();
Geometry polys = subdiv.getVoronoiDiagram(geomFact);
// clip polys to diagramEnv
return clipGeometryCollection(polys, diagramEnv);
}
private static Geometry clipGeometryCollection(Geometry geom, Envelope clipEnv)
{
Geometry clipPoly = geom.getFactory().toGeometry(clipEnv);
List clipped = new ArrayList();
for (int i = 0; i < geom.getNumGeometries(); i++) {
Geometry g = geom.getGeometryN(i);
Geometry result = null;
// don't clip unless necessary
if (clipEnv.contains(g.getEnvelopeInternal()))
result = g;
else if (clipEnv.intersects(g.getEnvelopeInternal())) {
result = clipPoly.intersection(g);
// keep vertex key info
result.setUserData(g.getUserData());
}
if (result != null && ! result.isEmpty()) {
clipped.add(result);
}
}
return geom.getFactory().createGeometryCollection(GeometryFactory.toGeometryArray(clipped));
}
}