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/*
* 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.overlay;
import java.util.*;
import com.vividsolutions.jts.geom.*;
import com.vividsolutions.jts.algorithm.*;
import com.vividsolutions.jts.geomgraph.*;
/**
* Constructs {@link Point}s from the nodes of an overlay graph.
* @version 1.7
*/
public class PointBuilder {
private OverlayOp op;
private GeometryFactory geometryFactory;
private List resultPointList = new ArrayList();
public PointBuilder(OverlayOp op, GeometryFactory geometryFactory, PointLocator ptLocator) {
this.op = op;
this.geometryFactory = geometryFactory;
// ptLocator is never used in this class
}
/**
* Computes the Point geometries which will appear in the result,
* given the specified overlay operation.
*
* @return a list of the Points objects in the result
*/
public List build(int opCode)
{
extractNonCoveredResultNodes(opCode);
/**
* It can happen that connected result nodes are still covered by
* result geometries, so must perform this filter.
* (For instance, this can happen during topology collapse).
*/
return resultPointList;
}
/**
* Determines nodes which are in the result, and creates {@link Point}s for them.
*
* This method determines nodes which are candidates for the result via their
* labelling and their graph topology.
*
* @param opCode the overlay operation
*/
private void extractNonCoveredResultNodes(int opCode)
{
// testing only
//if (true) return resultNodeList;
for (Iterator nodeit = op.getGraph().getNodes().iterator(); nodeit.hasNext(); ) {
Node n = (Node) nodeit.next();
// filter out nodes which are known to be in the result
if (n.isInResult())
continue;
// if an incident edge is in the result, then the node coordinate is included already
if (n.isIncidentEdgeInResult())
continue;
if (n.getEdges().getDegree() == 0 || opCode == OverlayOp.INTERSECTION) {
/**
* For nodes on edges, only INTERSECTION can result in edge nodes being included even
* if none of their incident edges are included
*/
Label label = n.getLabel();
if (OverlayOp.isResultOfOp(label, opCode)) {
filterCoveredNodeToPoint(n);
}
}
}
//System.out.println("connectedResultNodes collected = " + connectedResultNodes.size());
}
/**
* Converts non-covered nodes to Point objects and adds them to the result.
*
* A node is covered if it is contained in another element Geometry
* with higher dimension (e.g. a node point might be contained in a polygon,
* in which case the point can be eliminated from the result).
*
* @param n the node to test
*/
private void filterCoveredNodeToPoint(Node n)
{
Coordinate coord = n.getCoordinate();
if (! op.isCoveredByLA(coord)) {
Point pt = geometryFactory.createPoint(coord);
resultPointList.add(pt);
}
}
}