| gvSIG desktop 1

/*

 * Created on 09-oct-2006

 *

 * gvSIG. Sistema de Informaci?n Geogr?fica de la Generalitat Valenciana

 *

 * Copyright (C) 2004 IVER T.I. and Generalitat Valenciana.

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License

 * as published by the Free Software Foundation; either version 2

 * of the License, or (at your option) any later version.

 *

 * This program 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 General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,USA.

 *

 * For more information, contact:

 *

 *  Generalitat Valenciana

 *   Conselleria d'Infraestructures i Transport

 *   Av. Blasco Ib??ez, 50

 *   46010 VALENCIA

 *   SPAIN

 *

 *      +34 963862235

 *   gvsig@gva.es

 *      www.gvsig.gva.es

 *

 *    or

 *

 *   IVER T.I. S.A

 *   Salamanca 50

 *   46005 Valencia

 *   Spain

 *

 *   +34 963163400

 *   dac@iver.es

 */

/* CVS MESSAGES:

*

* $Id: SnapPolygonBuilder.java 38047 2012-03-01 17:46:39Z amaneiro $

* $Log$

* Revision 1.2  2007-03-06 17:08:59  caballero

* Exceptions

*

* Revision 1.1  2006/12/04 19:30:23  azabala

* *** empty log message ***

*

* Revision 1.2  2006/10/17 18:25:53  azabala

* *** empty log message ***

*

* Revision 1.1  2006/10/09 19:10:56  azabala

* First version in CVS

*

*

*/

package com.vividsolutions.jts.operation.overlay;

import java.util.ArrayList;

import java.util.Collection;

import java.util.Iterator;

import java.util.List;

import com.vividsolutions.jts.algorithm.CGAlgorithms;

import com.vividsolutions.jts.geom.Coordinate;

import com.vividsolutions.jts.geom.Envelope;

import com.vividsolutions.jts.geom.GeometryFactory;

import com.vividsolutions.jts.geom.LinearRing;

import com.vividsolutions.jts.geom.Polygon;

import com.vividsolutions.jts.geomgraph.DirectedEdge;

import com.vividsolutions.jts.geomgraph.EdgeRing;

import com.vividsolutions.jts.geomgraph.SnappingPlanarGraph;

import com.vividsolutions.jts.util.Assert;

public class SnapPolygonBuilder extends PolygonBuilder {

         private GeometryFactory geometryFactory;

          //private List dirEdgeList;

          //private NodeMap nodes;

          private List shellList        = new ArrayList();

          public SnapPolygonBuilder(GeometryFactory geometryFactory)

          {

                super(geometryFactory);

            this.geometryFactory = geometryFactory;

          }

          /**

           * Add a complete graph.

           * The graph is assumed to contain one or more polygons,

           * possibly with holes.

           */

          public void add(SnappingPlanarGraph graph)

          {

            add(graph.getEdgeEnds(), graph.getNodes());

          }

          /**

           * Add a set of edges and nodes, which form a graph.

           * The graph is assumed to contain one or more polygons,

           * possibly with holes.

           */

          public void add(Collection dirEdges, Collection nodes)

          {

                SnappingPlanarGraph.linkResultDirectedEdges(nodes);

            List maxEdgeRings = buildMaximalEdgeRings(dirEdges);

            List freeHoleList = new ArrayList();

            List edgeRings = buildMinimalEdgeRings(maxEdgeRings, shellList, freeHoleList);

            sortShellsAndHoles(edgeRings, shellList, freeHoleList);

            placeFreeHoles(shellList, freeHoleList);

          }

          public List getPolygons()

          {

            List resultPolyList = computePolygons(shellList);

            return resultPolyList;

          }

          /**

           * for all DirectedEdges in result, form them into MaximalEdgeRings

           */

          private List buildMaximalEdgeRings(Collection dirEdges)

          {

            List maxEdgeRings     = new ArrayList();

            for (Iterator it = dirEdges.iterator(); it.hasNext(); ) {

              DirectedEdge de = (DirectedEdge) it.next();

              if (de.isInResult() && de.getLabel().isArea() ) {

                // if this edge has not yet been processed

                if (de.getEdgeRing() == null) {

                  MaximalEdgeRing er = new MaximalEdgeRing(de, geometryFactory);

                  maxEdgeRings.add(er);

                  er.setInResult();

//        System.out.println("max node degree = " + er.getMaxDegree());

                }

              }

            }

            return maxEdgeRings;

          }

          private List buildMinimalEdgeRings(List maxEdgeRings, List shellList, List freeHoleList)

          {

            List edgeRings = new ArrayList();

            for (Iterator it = maxEdgeRings.iterator(); it.hasNext(); ) {

              MaximalEdgeRing er = (MaximalEdgeRing) it.next();

              if (er.getMaxNodeDegree() > 2) {

                er.linkDirectedEdgesForMinimalEdgeRings();

                List minEdgeRings = er.buildMinimalRings();

                // at this point we can go ahead and attempt to place holes, if this EdgeRing is a polygon

                EdgeRing shell = findShell(minEdgeRings);

                if (shell != null) {

                  placePolygonHoles(shell, minEdgeRings);

                  shellList.add(shell);

                }

                else {

                  freeHoleList.addAll(minEdgeRings);

                }

              }

              else {

                edgeRings.add(er);

              }

            }

            return edgeRings;

          }

          /**

           * This method takes a list of MinimalEdgeRings derived from a MaximalEdgeRing,

           * and tests whether they form a Polygon.  This is the case if there is a single shell

           * in the list.  In this case the shell is returned.

           * The other possibility is that they are a series of connected holes, in which case

           * no shell is returned.

           *

           * @return the shell EdgeRing, if there is one

           * @return null, if all the rings are holes

           */

          private EdgeRing findShell(List minEdgeRings)

          {

            int shellCount = 0;

            EdgeRing shell = null;

            for (Iterator it = minEdgeRings.iterator(); it.hasNext(); ) {

              EdgeRing er = (MinimalEdgeRing) it.next();

              if (! er.isHole()) {

                shell = er;

                shellCount++;

              }

            }

            Assert.isTrue(shellCount <= 1, "found two shells in MinimalEdgeRing list");

            return shell;

          }

          /**

           * This method assigns the holes for a Polygon (formed from a list of

           * MinimalEdgeRings) to its shell.

           * Determining the holes for a MinimalEdgeRing polygon serves two purposes:

           * <ul>

           * <li>it is faster than using a point-in-polygon check later on.

           * <li>it ensures correctness, since if the PIP test was used the point

           * chosen might lie on the shell, which might return an incorrect result from the

           * PIP test

           * </ul>

           */

          private void placePolygonHoles(EdgeRing shell, List minEdgeRings)

          {

            for (Iterator it = minEdgeRings.iterator(); it.hasNext(); ) {

              MinimalEdgeRing er = (MinimalEdgeRing) it.next();

              if (er.isHole()) {

                er.setShell(shell);

              }

            }

          }

          /**

           * For all rings in the input list,

           * determine whether the ring is a shell or a hole

           * and add it to the appropriate list.

           * Due to the way the DirectedEdges were linked,

           * a ring is a shell if it is oriented CW, a hole otherwise.

           */

          private void sortShellsAndHoles(List edgeRings, List shellList, List freeHoleList)

          {

            for (Iterator it = edgeRings.iterator(); it.hasNext(); ) {

              EdgeRing er = (EdgeRing) it.next();

//              er.setInResult();

              if (er.isHole() ) {

                freeHoleList.add(er);

              }

              else {

                shellList.add(er);

              }

            }

          }

          /**

           * This method determines finds a containing shell for all holes

           * which have not yet been assigned to a shell.

           * These "free" holes should

           * all be <b>properly</b> contained in their parent shells, so it is safe to use the

           * <code>findEdgeRingContaining</code> method.

           * (This is the case because any holes which are NOT

           * properly contained (i.e. are connected to their

           * parent shell) would have formed part of a MaximalEdgeRing

           * and been handled in a previous step).

           */

          private void placeFreeHoles(List shellList, List freeHoleList)

          {

            for (Iterator it = freeHoleList.iterator(); it.hasNext(); ) {

              EdgeRing hole = (EdgeRing) it.next();

              // only place this hole if it doesn't yet have a shell

              if (hole.getShell() == null) {

                EdgeRing shell = findEdgeRingContaining(hole, shellList);

                Assert.isTrue(shell != null, "unable to assign hole to a shell");

                hole.setShell(shell);

              }

            }

          }

          /**

           * Find the innermost enclosing shell EdgeRing containing the argument EdgeRing, if any.

           * The innermost enclosing ring is the <i>smallest</i> enclosing ring.

           * The algorithm used depends on the fact that:

           * <br>

           *  ring A contains ring B iff envelope(ring A) contains envelope(ring B)

           * <br>

           * This routine is only safe to use if the chosen point of the hole

           * is known to be properly contained in a shell

           * (which is guaranteed to be the case if the hole does not touch its shell)

           *

           * @return containing EdgeRing, if there is one

           * @return null if no containing EdgeRing is found

           */

          //TODO Estudiar como meter el snapping

          private EdgeRing findEdgeRingContaining(EdgeRing testEr, List shellList)

          {

            LinearRing testRing = testEr.getLinearRing();

            Envelope testEnv = testRing.getEnvelopeInternal();

            Coordinate testPt = testRing.getCoordinateN(0);

            EdgeRing minShell = null;

            Envelope minEnv = null;

            for (Iterator it = shellList.iterator(); it.hasNext(); ) {

              EdgeRing tryShell = (EdgeRing) it.next();

              LinearRing tryRing = tryShell.getLinearRing();

              Envelope tryEnv = tryRing.getEnvelopeInternal();

              if (minShell != null) minEnv = minShell.getLinearRing().getEnvelopeInternal();

              boolean isContained = false;

              if (tryEnv.contains(testEnv)

                  && CGAlgorithms.isPointInRing(testPt, tryRing.getCoordinates()) )

                isContained = true;

              // check if this new containing ring is smaller than the current minimum ring

              if (isContained) {

                if (minShell == null

                    || minEnv.contains(tryEnv)) {

                  minShell = tryShell;

                }

              }

            }

            return minShell;

          }

          private List computePolygons(List shellList)

          {

            List resultPolyList   = new ArrayList();

            // add Polygons for all shells

            for (Iterator it = shellList.iterator(); it.hasNext(); ) {

              EdgeRing er = (EdgeRing) it.next();

              Polygon poly = er.toPolygon(geometryFactory);

              resultPolyList.add(poly);

            }

            return resultPolyList;

          }

          /**

           * Checks the current set of shells (with their associated holes) to

           * see if any of them contain the point.

           */

          //TODO METER SNAPPING

          public boolean containsPoint(Coordinate p)

          {

            for (Iterator it = shellList.iterator(); it.hasNext(); ) {

              EdgeRing er = (EdgeRing) it.next();

              if (er.containsPoint(p))

               return true;

            }

            return false;

          }

}