/// <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>
/// 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>
/// 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);
}