/* * 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.linemerge; import java.util.ArrayList; import java.util.Collection; import java.util.Iterator; import com.vividsolutions.jts.geom.Geometry; import com.vividsolutions.jts.geom.GeometryComponentFilter; import com.vividsolutions.jts.geom.GeometryFactory; import com.vividsolutions.jts.geom.LineString; import com.vividsolutions.jts.planargraph.GraphComponent; import com.vividsolutions.jts.planargraph.Node; import com.vividsolutions.jts.util.Assert; /** * Merges a collection of linear components to form maximal-length linestrings. * <p> * Merging stops at nodes of degree 1 or degree 3 or more. * In other words, all nodes of degree 2 are merged together. * The exception is in the case of an isolated loop, which only has degree-2 nodes. * In this case one of the nodes is chosen as a starting point. * <p> * The direction of each * merged LineString will be that of the majority of the LineStrings from which it * was derived. * <p> * Any dimension of Geometry is handled - the constituent linework is extracted to * form the edges. The edges must be correctly noded; that is, they must only meet * at their endpoints. The LineMerger will accept non-noded input * but will not merge non-noded edges. * <p> * Input lines which are empty or contain only a single unique coordinate are not included * in the merging. * * @version 1.7 */ public class LineMerger { private LineMergeGraph graph = new LineMergeGraph(); private Collection mergedLineStrings = null; private GeometryFactory factory = null; /** * Creates a new line merger. * */ public LineMerger() { } /** * Adds a Geometry to be processed. May be called multiple times. * Any dimension of Geometry may be added; the constituent linework will be * extracted. * * @param geometry geometry to be line-merged */ public void add(Geometry geometry) { geometry.apply(new GeometryComponentFilter() { public void filter(Geometry component) { if (component instanceof LineString) { add((LineString)component); } } }); } /** * Adds a collection of Geometries to be processed. May be called multiple times. * Any dimension of Geometry may be added; the constituent linework will be * extracted. * * @param geometries the geometries to be line-merged */ public void add(Collection geometries) { mergedLineStrings = null; for (Iterator i = geometries.iterator(); i.hasNext(); ) { Geometry geometry = (Geometry) i.next(); add(geometry); } } private void add(LineString lineString) { if (factory == null) { this.factory = lineString.getFactory(); } graph.addEdge(lineString); } private Collection edgeStrings = null; private void merge() { if (mergedLineStrings != null) { return; } // reset marks (this allows incremental processing) GraphComponent.setMarked(graph.nodeIterator(), false); GraphComponent.setMarked(graph.edgeIterator(), false); edgeStrings = new ArrayList(); buildEdgeStringsForObviousStartNodes(); buildEdgeStringsForIsolatedLoops(); mergedLineStrings = new ArrayList(); for (Iterator i = edgeStrings.iterator(); i.hasNext(); ) { EdgeString edgeString = (EdgeString) i.next(); mergedLineStrings.add(edgeString.toLineString()); } } private void buildEdgeStringsForObviousStartNodes() { buildEdgeStringsForNonDegree2Nodes(); } private void buildEdgeStringsForIsolatedLoops() { buildEdgeStringsForUnprocessedNodes(); } private void buildEdgeStringsForUnprocessedNodes() { for (Iterator i = graph.getNodes().iterator(); i.hasNext(); ) { Node node = (Node) i.next(); if (!node.isMarked()) { Assert.isTrue(node.getDegree() == 2); buildEdgeStringsStartingAt(node); node.setMarked(true); } } } private void buildEdgeStringsForNonDegree2Nodes() { for (Iterator i = graph.getNodes().iterator(); i.hasNext(); ) { Node node = (Node) i.next(); if (node.getDegree() != 2) { buildEdgeStringsStartingAt(node); node.setMarked(true); } } } private void buildEdgeStringsStartingAt(Node node) { for (Iterator i = node.getOutEdges().iterator(); i.hasNext(); ) { LineMergeDirectedEdge directedEdge = (LineMergeDirectedEdge) i.next(); if (directedEdge.getEdge().isMarked()) { continue; } edgeStrings.add(buildEdgeStringStartingWith(directedEdge)); } } private EdgeString buildEdgeStringStartingWith(LineMergeDirectedEdge start) { EdgeString edgeString = new EdgeString(factory); LineMergeDirectedEdge current = start; do { edgeString.add(current); current.getEdge().setMarked(true); current = current.getNext(); } while (current != null && current != start); return edgeString; } /** * Gets the {@link LineString}s created by the merging process. * * @return the collection of merged LineStrings */ public Collection getMergedLineStrings() { merge(); return mergedLineStrings; } }