/*
* The JTS Topology Suite is a collection of Java classes that
* implement the fundamental operations required to validate a given
* geo-spatial data set to a known topological specification.
*
* Copyright (C) 2001 Vivid Solutions
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* For more information, contact:
*
* Vivid Solutions
* Suite #1A
* 2328 Government Street
* Victoria BC V8T 5G5
* Canada
*
* (250)385-6040
* www.vividsolutions.com
*/
package com.vividsolutions.jts.operation;
import java.util.*;
import com.vividsolutions.jts.algorithm.BoundaryNodeRule;
import com.vividsolutions.jts.geom.*;
/**
* Computes the boundary of a {@link Geometry}.
* Allows specifying the {@link BoundaryNodeRule} to be used.
* This operation will always return a {@link Geometry} of the appropriate
* dimension for the boundary (even if the input geometry is empty).
* The boundary of zero-dimensional geometries (Points) is
* always the empty {@link GeometryCollection}.
*
* @author Martin Davis
* @version 1.7
*/
public class BoundaryOp
{
private Geometry geom;
private GeometryFactory geomFact;
private BoundaryNodeRule bnRule;
public BoundaryOp(Geometry geom)
{
this(geom, BoundaryNodeRule.MOD2_BOUNDARY_RULE);
}
public BoundaryOp(Geometry geom, BoundaryNodeRule bnRule)
{
this.geom = geom;
geomFact = geom.getFactory();
this.bnRule = bnRule;
}
public Geometry getBoundary()
{
if (geom instanceof LineString) return boundaryLineString((LineString) geom);
if (geom instanceof MultiLineString) return boundaryMultiLineString((MultiLineString) geom);
return geom.getBoundary();
}
private MultiPoint getEmptyMultiPoint()
{
return geomFact.createMultiPoint((CoordinateSequence) null);
}
private Geometry boundaryMultiLineString(MultiLineString mLine)
{
if (geom.isEmpty()) {
return getEmptyMultiPoint();
}
Coordinate[] bdyPts = computeBoundaryCoordinates(mLine);
// return Point or MultiPoint
if (bdyPts.length == 1) {
return geomFact.createPoint(bdyPts[0]);
}
// this handles 0 points case as well
return geomFact.createMultiPoint(bdyPts);
}
/*
// MD - superseded
private Coordinate[] computeBoundaryFromGeometryGraph(MultiLineString mLine)
{
GeometryGraph g = new GeometryGraph(0, mLine, bnRule);
Coordinate[] bdyPts = g.getBoundaryPoints();
return bdyPts;
}
*/
private Map endpointMap;
private Coordinate[] computeBoundaryCoordinates(MultiLineString mLine)
{
List bdyPts = new ArrayList();
endpointMap = new TreeMap();
for (int i = 0; i < mLine.getNumGeometries(); i++) {
LineString line = (LineString) mLine.getGeometryN(i);
if (line.getNumPoints() == 0)
continue;
addEndpoint(line.getCoordinateN(0));
addEndpoint(line.getCoordinateN(line.getNumPoints() - 1));
}
for (Iterator it = endpointMap.entrySet().iterator(); it.hasNext(); ) {
Map.Entry entry = (Map.Entry) it.next();
Counter counter = (Counter) entry.getValue();
int valence = counter.count;
if (bnRule.isInBoundary(valence)) {
bdyPts.add(entry.getKey());
}
}
return CoordinateArrays.toCoordinateArray(bdyPts);
}
private void addEndpoint(Coordinate pt)
{
Counter counter = (Counter) endpointMap.get(pt);
if (counter == null) {
counter = new Counter();
endpointMap.put(pt, counter);
}
counter.count++;
}
private Geometry boundaryLineString(LineString line)
{
if (geom.isEmpty()) {
return getEmptyMultiPoint();
}
if (line.isClosed()) {
// check whether endpoints of valence 2 are on the boundary or not
boolean closedEndpointOnBoundary = bnRule.isInBoundary(2);
if (closedEndpointOnBoundary) {
return line.getStartPoint();
}
else {
return geomFact.createMultiPoint((Coordinate[]) null);
}
}
return geomFact.createMultiPoint(new Point[]{
line.getStartPoint(),
line.getEndPoint()
});
}
}
/**
* Stores an integer count, for use as a Map entry.
*
* @author Martin Davis
* @version 1.7
*/
class Counter
{
/**
* The value of the count
*/
int count;
}