/// <summary>
/// Finds and removes all cut edges from the graph.
/// </summary>
/// <returns>A list of the <c>LineString</c>s forming the removed cut edges.</returns>
public IList <ILineString> DeleteCutEdges()
{
ComputeNextCWEdges();
// label the current set of edgerings
FindLabeledEdgeRings(dirEdges);
/*
* Cut Edges are edges where both dirEdges have the same label.
* Delete them, and record them
*/
IList <ILineString> cutLines = new List <ILineString>();
foreach (PolygonizeDirectedEdge de in dirEdges)
{
if (de.IsMarked)
{
continue;
}
PolygonizeDirectedEdge sym = (PolygonizeDirectedEdge)de.Sym;
if (de.Label == sym.Label)
{
de.Marked = true;
sym.Marked = true;
// save the line as a cut edge
PolygonizeEdge e = (PolygonizeEdge)de.Edge;
cutLines.Add(e.Line);
}
}
return(cutLines);
}
/// <summary>
/// Add a <c>LineString</c> forming an edge of the polygon graph.
/// </summary>
/// <param name="line">The line to add.</param>
public void AddEdge(ILineString line)
{
if (line.IsEmpty)
{
return;
}
Coordinate[] linePts = CoordinateArrays.RemoveRepeatedPoints(line.Coordinates);
if (linePts.Length < 2)
{
return;
}
Coordinate startPt = linePts[0];
Coordinate endPt = linePts[linePts.Length - 1];
Node nStart = GetNode(startPt);
Node nEnd = GetNode(endPt);
DirectedEdge de0 = new PolygonizeDirectedEdge(nStart, nEnd, linePts[1], true);
DirectedEdge de1 = new PolygonizeDirectedEdge(nEnd, nStart, linePts[linePts.Length - 2], false);
Edge edge = new PolygonizeEdge(line);
edge.SetDirectedEdges(de0, de1);
Add(edge);
}
/// <summary>
///
/// </summary>
/// <param name="startDE"></param>
/// <returns></returns>
private EdgeRing FindEdgeRing(PolygonizeDirectedEdge startDE)
{
var er = new EdgeRing(_factory);
er.Build(startDE);
return(er);
}
/// <summary>
///
/// </summary>
/// <param name="node"></param>
private static void ComputeNextCWEdges(Node node)
{
DirectedEdgeStar deStar = node.OutEdges;
PolygonizeDirectedEdge startDE = null;
PolygonizeDirectedEdge prevDE = null;
// the edges are stored in CCW order around the star
foreach (PolygonizeDirectedEdge outDE in deStar.Edges)
{
if (outDE.IsMarked)
{
continue;
}
if (startDE == null)
{
startDE = outDE;
}
if (prevDE != null)
{
PolygonizeDirectedEdge sym = (PolygonizeDirectedEdge)prevDE.Sym;
sym.Next = outDE;
}
prevDE = outDE;
}
if (prevDE != null)
{
PolygonizeDirectedEdge sym = (PolygonizeDirectedEdge)prevDE.Sym;
sym.Next = startDE;
}
}
/// <summary>
/// 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
/// </summary>
/// <param name="node"></param>
/// <param name="label"></param>
private static void ComputeNextCCWEdges(Node node, long label)
{
DirectedEdgeStar deStar = node.OutEdges;
//PolyDirectedEdge lastInDE = null;
PolygonizeDirectedEdge firstOutDE = null;
PolygonizeDirectedEdge prevInDE = null;
// the edges are stored in CCW order around the star
IList <DirectedEdge> edges = deStar.Edges;
//for (IEnumerator i = deStar.Edges.GetEnumerator(); i.MoveNext(); ) {
for (int i = edges.Count - 1; i >= 0; i--)
{
PolygonizeDirectedEdge de = (PolygonizeDirectedEdge)edges[i];
PolygonizeDirectedEdge sym = (PolygonizeDirectedEdge)de.Sym;
PolygonizeDirectedEdge outDE = null;
if (de.Label == label)
{
outDE = de;
}
PolygonizeDirectedEdge inDE = null;
if (sym.Label == 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.Next = outDE;
prevInDE = null;
}
if (firstOutDE == null)
{
firstOutDE = outDE;
}
}
}
if (prevInDE != null)
{
Assert.IsTrue(firstOutDE != null);
prevInDE.Next = firstOutDE;
}
}
/// <summary>
/// Traverses the polygonized edge rings in the graph
/// and computes the depth parity (odd or even)
/// relative to the exterior of the graph.
///
/// If the client has requested that the output
/// be polygonally valid, only odd polygons will be constructed.
/// </summary>
public void ComputeDepthParity()
{
while (true)
{
PolygonizeDirectedEdge de = null; //findLowestDirEdge();
if (de == null)
{
return;
}
ComputeDepthParity(de);
}
}
public void Build(PolygonizeDirectedEdge startDE)
{
PolygonizeDirectedEdge de = startDE;
do
{
Add(de);
de.Ring = this;
de = de.Next;
Utilities.Assert.IsTrue(de != null, "found null DE in ring");
Utilities.Assert.IsTrue(de == startDE || !de.IsInRing, "found DE already in ring");
} while (de != startDE);
}
/// <summary>
/// Traverses a ring of DirectedEdges, accumulating them into a list.
/// This assumes that all dangling directed edges have been removed
/// from the graph, so that there is always a next dirEdge.
/// </summary>
/// <param name="startDE">The DirectedEdge to start traversing at.</param>
/// <returns>A List of DirectedEdges that form a ring.</returns>
private static IEnumerable <DirectedEdge> FindDirEdgesInRing(PolygonizeDirectedEdge startDE)
{
PolygonizeDirectedEdge de = startDE;
IList <DirectedEdge> edges = new List <DirectedEdge>();
do
{
edges.Add(de);
de = de.Next;
Assert.IsTrue(de != null, "found null DE in ring");
Assert.IsTrue(de == startDE || !de.IsInRing, "found DE already in ring");
}while (de != startDE);
return(edges);
}
/// <summary>
/// Deletes all edges at a node.
/// </summary>
/// <param name="node"></param>
public static void DeleteAllEdges(Node node)
{
IList <DirectedEdge> edges = node.OutEdges.Edges;
foreach (PolygonizeDirectedEdge de in edges)
{
de.Marked = true;
PolygonizeDirectedEdge sym = (PolygonizeDirectedEdge)de.Sym;
if (sym != null)
{
sym.Marked = true;
}
}
}
/**
* Traverses a ring of DirectedEdges, accumulating them into a list.
* This assumes that all dangling directed edges have been removed
* from the graph, so that there is always a next dirEdge.
*
* @param startDE the DirectedEdge to start traversing at
* @return a List of DirectedEdges that form a ring
*/
public static List <DirectedEdge> FindDirEdgesInRing(PolygonizeDirectedEdge startDE)
{
var de = startDE;
var edges = new List <DirectedEdge>();
do
{
edges.Add(de);
de = de.Next;
Utilities.Assert.IsTrue(de != null, "found null DE in ring");
Utilities.Assert.IsTrue(de == startDE || !de.IsInRing, "found DE already in ring");
} while (de != startDE);
return(edges);
}
/// <summary>
///
/// </summary>
/// <param name="startDE"></param>
/// <returns></returns>
private EdgeRing FindEdgeRing(PolygonizeDirectedEdge startDE)
{
PolygonizeDirectedEdge de = startDE;
EdgeRing er = new EdgeRing(_factory);
do
{
er.Add(de);
de.Ring = er;
de = de.Next;
Assert.IsTrue(de != null, "found null DE in ring");
Assert.IsTrue(de == startDE || !de.IsInRing, "found DE already in ring");
}while (de != startDE);
return(er);
}
/// <summary>
/// Marks all edges from the graph which are "dangles".
/// Dangles are which are incident on a node with degree 1.
/// This process is recursive, since removing a dangling edge
/// may result in another edge becoming a dangle.
/// In order to handle large recursion depths efficiently,
/// an explicit recursion stack is used.
/// </summary>
/// <returns>A List containing the <see cref="ILineString"/>s that formed dangles.</returns>
public ICollection <ILineString> DeleteDangles()
{
var nodesToRemove = FindNodesOfDegree(1);
HashSet <ILineString> dangleLines = new HashSet <ILineString>();
Stack <Node> nodeStack = new Stack <Node>();
foreach (Node node in nodesToRemove)
{
nodeStack.Push(node);
}
while (nodeStack.Count != 0)
{
Node node = nodeStack.Pop();
DeleteAllEdges(node);
IList <DirectedEdge> nodeOutEdges = node.OutEdges.Edges;
foreach (PolygonizeDirectedEdge de in nodeOutEdges)
{
// delete this edge and its sym
de.Marked = true;
PolygonizeDirectedEdge sym = (PolygonizeDirectedEdge)de.Sym;
if (sym != null)
{
sym.Marked = true;
}
// save the line as a dangle
PolygonizeEdge e = (PolygonizeEdge)de.Edge;
dangleLines.Add(e.Line);
Node toNode = de.ToNode;
// add the toNode to the list to be processed, if it is now a dangle
if (GetDegreeNonDeleted(toNode) == 1)
{
nodeStack.Push(toNode);
}
}
}
var dangleArray = new ILineString[dangleLines.Count];
dangleLines.CopyTo(dangleArray, 0);
return(new ReadOnlyCollection <ILineString>(dangleArray));
//new ArrayList(dangleLines.CastPlatform());
}
/// <summary>
/// Add a <c>LineString</c> forming an edge of the polygon graph.
/// </summary>
/// <param name="line">The line to add.</param>
public void AddEdge(ILineString line)
{
if (line.IsEmpty)
return;
Coordinate[] linePts = CoordinateArrays.RemoveRepeatedPoints(line.Coordinates);
Coordinate startPt = linePts[0];
Coordinate endPt = linePts[linePts.Length - 1];
Node nStart = GetNode(startPt);
Node nEnd = GetNode(endPt);
DirectedEdge de0 = new PolygonizeDirectedEdge(nStart, nEnd, linePts[1], true);
DirectedEdge de1 = new PolygonizeDirectedEdge(nEnd, nStart, linePts[linePts.Length - 2], false);
Edge edge = new PolygonizeEdge(line);
edge.SetDirectedEdges(de0, de1);
Add(edge);
}
/// <summary>
/// Updates the included status for currently non-included shells
/// based on whether they are adjacent to an included shell.
/// </summary>
internal void UpdateIncluded()
{
if (IsHole)
{
return;
}
for (int i = 0; i < _deList.Count; i++)
{
PolygonizeDirectedEdge de = (PolygonizeDirectedEdge)_deList[i];
EdgeRing adjShell = ((PolygonizeDirectedEdge)de.Sym).Ring.Shell;
if (adjShell != null && adjShell.IsIncludedSet)
{
// adjacent ring has been processed, so set included to inverse of adjacent included
IsIncluded = !adjShell.IsIncluded;
return;
}
}
}
/// <summary>
/// Finds all nodes in a maximal edgering which are self-intersection nodes
/// </summary>
/// <param name="startDE"></param>
/// <param name="label"></param>
/// <returns>
/// The list of intersection nodes found,
/// or null if no intersection nodes were found.
/// </returns>
private static IEnumerable <Node> FindIntersectionNodes(PolygonizeDirectedEdge startDE, long label)
{
PolygonizeDirectedEdge de = startDE;
IList <Node> intNodes = null;
do
{
Node node = de.FromNode;
if (GetDegree(node, label) > 1)
{
if (intNodes == null)
{
intNodes = new List <Node>();
}
intNodes.Add(node);
}
de = de.Next;
Assert.IsTrue(de != null, "found null DE in ring");
Assert.IsTrue(de == startDE || !de.IsInRing, "found DE already in ring");
}while (de != startDE);
return(intNodes);
}
/// <summary>
///
/// </summary>
/// <param name="startDE"></param>
/// <returns></returns>
private EdgeRing FindEdgeRing(PolygonizeDirectedEdge startDE)
{
PolygonizeDirectedEdge de = startDE;
EdgeRing er = new EdgeRing(_factory);
do
{
er.Add(de);
de.Ring = er;
de = de.Next;
Assert.IsTrue(de != null, "found null DE in ring");
Assert.IsTrue(de == startDE || ! de.IsInRing, "found DE already in ring");
}
while (de != startDE);
return er;
}
/// <summary>
/// Finds all nodes in a maximal edgering which are self-intersection nodes
/// </summary>
/// <param name="startDE"></param>
/// <param name="label"></param>
/// <returns>
/// The list of intersection nodes found,
/// or null if no intersection nodes were found.
/// </returns>
private static IEnumerable<Node> FindIntersectionNodes(PolygonizeDirectedEdge startDE, long label)
{
PolygonizeDirectedEdge de = startDE;
IList<Node> intNodes = null;
do
{
Node node = de.FromNode;
if (GetDegree(node, label) > 1)
{
if (intNodes == null)
intNodes = new List<Node>();
intNodes.Add(node);
}
de = de.Next;
Assert.IsTrue(de != null, "found null DE in ring");
Assert.IsTrue(de == startDE || ! de.IsInRing, "found DE already in ring");
}
while (de != startDE);
return intNodes;
}
/// <summary>
///
/// </summary>
/// <param name="startDE"></param>
/// <returns></returns>
private EdgeRing FindEdgeRing(PolygonizeDirectedEdge startDE)
{
var er = new EdgeRing(_factory);
er.Build(startDE);
return er;
}
///<summary>
/// Traverses all connected edges, computing the depth parity of the associated polygons.
///</summary>
/// <param name="de"></param>
private void ComputeDepthParity(PolygonizeDirectedEdge de)
{
}
///<summary>
/// Traverses all connected edges, computing the depth parity of the associated polygons.
///</summary>
/// <param name="de"></param>
private void ComputeDepthParity(PolygonizeDirectedEdge de)
{
}
/// <summary>
/// Traverses a ring of DirectedEdges, accumulating them into a list.
/// This assumes that all dangling directed edges have been removed
/// from the graph, so that there is always a next dirEdge.
/// </summary>
/// <param name="startDE">The DirectedEdge to start traversing at.</param>
/// <returns>A List of DirectedEdges that form a ring.</returns>
private static IEnumerable<DirectedEdge> FindDirEdgesInRing(PolygonizeDirectedEdge startDE)
{
PolygonizeDirectedEdge de = startDE;
IList<DirectedEdge> edges = new List<DirectedEdge>();
do
{
edges.Add(de);
de = de.Next;
Assert.IsTrue(de != null, "found null DE in ring");
Assert.IsTrue(de == startDE || ! de.IsInRing, "found DE already in ring");
}
while (de != startDE);
return edges;
}
