/* * 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; }