File: PolygonizeGraph.cpp

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/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2005-2006 Refractions Research Inc.
 * Copyright (C) 2001-2002 Vivid Solutions Inc.
 *
 * This is free software; you can redistribute and/or modify it under
 * the terms of the GNU Lesser General Public Licence as published
 * by the Free Software Foundation. 
 * See the COPYING file for more information.
 *
 **********************************************************************
 *
 * Last port: operation/polygonize/PolygonizeGraph.java rev. 6/138 (JTS-1.10)
 *
 **********************************************************************/

#include <geos/operation/polygonize/PolygonizeGraph.h>
#include <geos/operation/polygonize/PolygonizeDirectedEdge.h>
#include <geos/operation/polygonize/PolygonizeEdge.h>
#include <geos/operation/polygonize/EdgeRing.h>
#include <geos/planargraph/Node.h>
#include <geos/planargraph/DirectedEdgeStar.h>
#include <geos/planargraph/DirectedEdge.h>
#include <geos/geom/CoordinateSequence.h>
#include <geos/geom/LineString.h>

#include <cassert>
#include <vector>
#include <set>

//using namespace std;
using namespace geos::planargraph;
using namespace geos::geom;

// Define the following to add assertions on downcasts
//#define GEOS_CAST_PARANOIA 1

namespace geos {
namespace operation { // geos.operation
namespace polygonize { // geos.operation.polygonize

int
PolygonizeGraph::getDegreeNonDeleted(Node *node)
{
	std::vector<DirectedEdge*> &edges=node->getOutEdges()->getEdges();
	int degree=0;
	for(unsigned int i=0; i<edges.size(); ++i) {
		PolygonizeDirectedEdge *de=(PolygonizeDirectedEdge*)edges[i];
		if (!de->isMarked()) ++degree;
	}
	return degree;
}

int
PolygonizeGraph::getDegree(Node *node, long label)
{
	std::vector<DirectedEdge*> &edges=node->getOutEdges()->getEdges();
	int degree=0;
	for(unsigned int i=0; i<edges.size(); ++i)
	{
		PolygonizeDirectedEdge *de=(PolygonizeDirectedEdge*)edges[i];
		if (de->getLabel()==label) ++degree;
	}
	return degree;
}

/**
 * Deletes all edges at a node
 */
void
PolygonizeGraph::deleteAllEdges(Node *node)
{
	std::vector<DirectedEdge*> &edges=node->getOutEdges()->getEdges();
	for(unsigned int i=0; i<edges.size(); ++i) {
		PolygonizeDirectedEdge *de=(PolygonizeDirectedEdge*)edges[i];
		de->setMarked(true);
		PolygonizeDirectedEdge *sym=(PolygonizeDirectedEdge*) de->getSym();
		if (sym!=NULL)
			sym->setMarked(true);
	}
}

/*
 * Create a new polygonization graph.
 */
PolygonizeGraph::PolygonizeGraph(const GeometryFactory *newFactory):
	factory(newFactory)
{
}

/*
 * Destroy a PolygonizeGraph
 */
PolygonizeGraph::~PolygonizeGraph()
{
	unsigned int i;
	for (i=0; i<newEdges.size(); i++)
		delete newEdges[i];
	for (i=0; i<newDirEdges.size(); i++)
		delete newDirEdges[i];
	for (i=0; i<newNodes.size(); i++)
		delete newNodes[i];
	for (i=0; i<newEdgeRings.size(); i++)
		delete newEdgeRings[i];
	for (i=0; i<newCoords.size(); i++) delete newCoords[i];
}

/*
 * Add a LineString forming an edge of the polygon graph.
 * @param line the line to add
 */
void
PolygonizeGraph::addEdge(const LineString *line)
{
	if (line->isEmpty()) return;

	CoordinateSequence *linePts=CoordinateSequence::removeRepeatedPoints(line->getCoordinatesRO());

	/*
	 * This would catch invalid linestrings
	 * (containing duplicated points only)
	 */
	if ( linePts->getSize() < 2 )
	{
		delete linePts;
		return;
	}

	const Coordinate& startPt=linePts->getAt(0);
	const Coordinate& endPt=linePts->getAt(linePts->getSize()-1);
	Node *nStart=getNode(startPt);
	Node *nEnd=getNode(endPt);
	DirectedEdge *de0=new PolygonizeDirectedEdge(nStart, nEnd, linePts->getAt(1), true);
	newDirEdges.push_back(de0);
	DirectedEdge *de1=new PolygonizeDirectedEdge(nEnd, nStart,
			linePts->getAt(linePts->getSize()-2), false);
	newDirEdges.push_back(de1);
	Edge *edge=new PolygonizeEdge(line);
	newEdges.push_back(edge);
	edge->setDirectedEdges(de0, de1);
	add(edge);

	newCoords.push_back(linePts);
}

Node *
PolygonizeGraph::getNode(const Coordinate& pt)
{
	Node *node=findNode(pt);
	if (node==NULL) {
		node=new Node(pt);
		newNodes.push_back(node);
		// ensure node is only added once to graph
		add(node);
	}
	return node;
}

void
PolygonizeGraph::computeNextCWEdges()
{
	typedef std::vector<Node*> Nodes;
	Nodes pns; getNodes(pns);
	// set the next pointers for the edges around each node
	for(Nodes::size_type i=0, in=pns.size(); i<in; ++i) {
		Node *node=pns[i];
		computeNextCWEdges(node);
	}
}

/* private */
void
PolygonizeGraph::convertMaximalToMinimalEdgeRings(
		std::vector<PolygonizeDirectedEdge*> &ringEdges)
{
	typedef std::vector<Node*> IntersectionNodes;
	typedef std::vector<PolygonizeDirectedEdge*> RingEdges;

	IntersectionNodes intNodes;
	for(RingEdges::size_type i=0, in=ringEdges.size();
			i<in; ++i)
	{
		PolygonizeDirectedEdge *de = ringEdges[i];
		long label=de->getLabel();
		findIntersectionNodes(de, label, intNodes);

		// set the next pointers for the edges around each node
		for(IntersectionNodes::size_type j=0, jn=intNodes.size();
				j<jn; ++j)
		{
			Node *node=intNodes[j];
			computeNextCCWEdges(node, label);
		}

		intNodes.clear(); 
	}
}

/* private static */
void
PolygonizeGraph::findIntersectionNodes(PolygonizeDirectedEdge *startDE,
		long label, std::vector<Node*>& intNodes)
{
	PolygonizeDirectedEdge *de=startDE;
	do {
		Node *node=de->getFromNode();
		if (getDegree(node, label) > 1) {
			intNodes.push_back(node);
		}
		de=de->getNext();
		assert(de!=NULL); // found NULL DE in ring
		assert(de==startDE || !de->isInRing()); // found DE already in ring
	} while (de!=startDE);
}

/* public */
void
PolygonizeGraph::getEdgeRings(std::vector<EdgeRing*>& edgeRingList)
{
	// maybe could optimize this, since most of these pointers should
	// be set correctly already
	// by deleteCutEdges()
	computeNextCWEdges();

	// clear labels of all edges in graph
	label(dirEdges, -1);
	std::vector<PolygonizeDirectedEdge*> maximalRings;
	findLabeledEdgeRings(dirEdges, maximalRings);
	convertMaximalToMinimalEdgeRings(maximalRings);
	maximalRings.clear(); // not needed anymore

	// find all edgerings
	for(unsigned int i=0; i<dirEdges.size(); ++i)
	{
		PolygonizeDirectedEdge *de=(PolygonizeDirectedEdge*)dirEdges[i];
		if (de->isMarked()) continue;
		if (de->isInRing()) continue;
		EdgeRing *er=findEdgeRing(de);
		edgeRingList.push_back(er);
	}
}

/* static private */
void
PolygonizeGraph::findLabeledEdgeRings(std::vector<DirectedEdge*> &dirEdges,
		std::vector<PolygonizeDirectedEdge*> &edgeRingStarts)
{
	typedef std::vector<DirectedEdge*> Edges;

	Edges edges;

	// label the edge rings formed
	long currLabel=1;
	for(Edges::size_type i=0, n=dirEdges.size(); i<n; ++i)
	{
#ifdef GEOS_CAST_PARANOIA
		assert(dynamic_cast<PolygonizeDirectedEdge*>(dirEdges[i]));
#endif
		PolygonizeDirectedEdge *de =
			static_cast<PolygonizeDirectedEdge*>(dirEdges[i]);

		if (de->isMarked()) continue;
		if (de->getLabel() >= 0) continue;
		edgeRingStarts.push_back(de);

		findDirEdgesInRing(de, edges);
		label(edges, currLabel);
		edges.clear(); 

		++currLabel;
	}
}

/* public */
void
PolygonizeGraph::deleteCutEdges(std::vector<const LineString*> &cutLines)
{
	computeNextCWEdges();

	typedef std::vector<PolygonizeDirectedEdge*> DirEdges;

	// label the current set of edgerings
	DirEdges junk;
	findLabeledEdgeRings(dirEdges, junk);
	junk.clear(); // not needed anymore

	/*
	 * Cut Edges are edges where both dirEdges have the same label.
	 * Delete them, and record them
	 */
	for (DirEdges::size_type i=0, in=dirEdges.size(); i<in; ++i)
	{
		DirectedEdge *de_ = dirEdges[i];
#ifdef GEOS_CAST_PARANOIA
		assert(dynamic_cast<PolygonizeDirectedEdge*>(de_));
#endif
		PolygonizeDirectedEdge *de =
			static_cast<PolygonizeDirectedEdge*>(de_);

		if (de->isMarked()) continue;

		DirectedEdge *sym_ = de->getSym();
#ifdef GEOS_CAST_PARANOIA
		assert(dynamic_cast<PolygonizeDirectedEdge*>(sym_));
#endif
		PolygonizeDirectedEdge *sym =
			static_cast<PolygonizeDirectedEdge*>(sym_);

		if (de->getLabel()==sym->getLabel())
		{
			de->setMarked(true);
			sym->setMarked(true);

			// save the line as a cut edge
			Edge *e_ = de->getEdge();
#ifdef GEOS_CAST_PARANOIA
			assert(dynamic_cast<PolygonizeEdge*>(e_));
#endif
			PolygonizeEdge *e = static_cast<PolygonizeEdge*>(e_);

			cutLines.push_back(e->getLine());
		}
	}
}

void
PolygonizeGraph::label(std::vector<DirectedEdge*> &dirEdges, long label)
{
	for(unsigned int i=0; i<dirEdges.size(); ++i)
	{
		PolygonizeDirectedEdge *de=(PolygonizeDirectedEdge*)dirEdges[i];
		de->setLabel(label);
	}
}

void
PolygonizeGraph::computeNextCWEdges(Node *node)
{
	DirectedEdgeStar *deStar=node->getOutEdges();
	PolygonizeDirectedEdge *startDE=NULL;
	PolygonizeDirectedEdge *prevDE=NULL;

	// the edges are stored in CCW order around the star
	std::vector<DirectedEdge*> &pde=deStar->getEdges();
	for(unsigned int i=0; i<pde.size(); ++i) {
		PolygonizeDirectedEdge *outDE=(PolygonizeDirectedEdge*)pde[i];
		if (outDE->isMarked()) continue;
		if (startDE==NULL)
			startDE=outDE;
		if (prevDE!=NULL) {
			PolygonizeDirectedEdge *sym=(PolygonizeDirectedEdge*) prevDE->getSym();
			sym->setNext(outDE);
		}
		prevDE=outDE;
	}
	if (prevDE!=NULL) {
		PolygonizeDirectedEdge *sym=(PolygonizeDirectedEdge*) prevDE->getSym();
		sym->setNext(startDE);
	}
}

/**
 * Computes the next edge pointers going CCW around the given node, for the
 * given edgering label.
 * This algorithm has the effect of converting maximal edgerings into
 * minimal edgerings
 */
void
PolygonizeGraph::computeNextCCWEdges(Node *node, long label)
{
	DirectedEdgeStar *deStar=node->getOutEdges();
	PolygonizeDirectedEdge *firstOutDE=NULL;
	PolygonizeDirectedEdge *prevInDE=NULL;

	// the edges are stored in CCW order around the star
	std::vector<DirectedEdge*> &edges=deStar->getEdges();

	/*
	 * Must use a SIGNED int here to allow for beak condition
	 * to be true.
	 */
	for(int i=static_cast<int>(edges.size())-1; i>=0; --i)
	{
		PolygonizeDirectedEdge *de=(PolygonizeDirectedEdge*)edges[i];
		PolygonizeDirectedEdge *sym=(PolygonizeDirectedEdge*) de->getSym();
		PolygonizeDirectedEdge *outDE=NULL;
		if (de->getLabel()==label) outDE=de;
		PolygonizeDirectedEdge *inDE=NULL;
		if (sym->getLabel()==label) inDE= sym;
		if (outDE==NULL && inDE==NULL) continue; // this edge is not in edgering
		if (inDE != NULL) {
			prevInDE=inDE;
		}
		if (outDE != NULL) {
			if (prevInDE != NULL) {
				prevInDE->setNext(outDE);
				prevInDE=NULL;
			}
			if (firstOutDE==NULL)
				firstOutDE=outDE;
		}
	}
	if (prevInDE != NULL) {
		assert(firstOutDE != NULL);
		prevInDE->setNext(firstOutDE);
	}
}

/* static private */
void
PolygonizeGraph::findDirEdgesInRing(PolygonizeDirectedEdge *startDE,
		std::vector<DirectedEdge*>& edges)
{
	PolygonizeDirectedEdge *de=startDE;
	do {
		edges.push_back(de);
		de=de->getNext();
		assert(de != NULL); // found NULL DE in ring
		assert(de==startDE || !de->isInRing()); // found DE already in ring
	} while (de != startDE);
}

EdgeRing *
PolygonizeGraph::findEdgeRing(PolygonizeDirectedEdge *startDE)
{
	PolygonizeDirectedEdge *de=startDE;
	EdgeRing *er=new EdgeRing(factory);
	// Now, when will we delete those EdgeRings ?
	newEdgeRings.push_back(er);
	do {
		er->add(de);
		de->setRing(er);
		de=de->getNext();
		assert(de != NULL); // found NULL DE in ring
		assert(de==startDE || ! de->isInRing()); // found DE already in ring
	} while (de != startDE);
	return er;
}

/* public */
void
PolygonizeGraph::deleteDangles(std::vector<const LineString*>& dangleLines)
{
	std::vector<Node*> nodeStack;
	findNodesOfDegree(1, nodeStack);

	std::set<const LineString*> uniqueDangles;

	while (!nodeStack.empty()) {
		Node *node=nodeStack.back(); 
		nodeStack.pop_back();
		deleteAllEdges(node);
		std::vector<DirectedEdge*> &nodeOutEdges=node->getOutEdges()->getEdges();
		for(unsigned int j=0; j<nodeOutEdges.size(); ++j)
		{
			PolygonizeDirectedEdge *de=(PolygonizeDirectedEdge*)nodeOutEdges[j];
			// delete this edge and its sym
			de->setMarked(true);
			PolygonizeDirectedEdge *sym=(PolygonizeDirectedEdge*) de->getSym();
			if (sym != NULL)
				sym->setMarked(true);
			// save the line as a dangle
			PolygonizeEdge *e=(PolygonizeEdge*) de->getEdge();
			const LineString* ls = e->getLine();
			if ( uniqueDangles.insert(ls).second )
				dangleLines.push_back(ls);
			Node *toNode=de->getToNode();
			// add the toNode to the list to be processed,
			// if it is now a dangle
			if (getDegreeNonDeleted(toNode)==1)
				nodeStack.push_back(toNode);
		}
	}

}

} // namespace geos.operation.polygonize
} // namespace geos.operation
} // namespace geos