/// <summary>
///
/// </summary>
/// <param name="g0"></param>
/// <param name="g1"></param>
public OverlayOp(IGeometry g0, IGeometry g1)
: base(g0, g1)
{
graph = new PlanarGraph(new OverlayNodeFactory());
/*
* Use factory of primary point.
* Note that this does NOT handle mixed-precision arguments
* where the second arg has greater precision than the first.
*/
geomFact = g0.Factory;
}
private IList CreateSubgraphs(PlanarGraph graph)
{
ArrayList subgraphList = new ArrayList();
foreach(object obj in graph.Nodes)
{
Node node = (Node)obj;
if (!node.IsVisited)
{
BufferSubgraph subgraph = new BufferSubgraph();
subgraph.Create(node);
subgraphList.Add(subgraph);
}
}
/*
* Sort the subgraphs in descending order of their rightmost coordinate.
* This ensures that when the Polygons for the subgraphs are built,
* subgraphs for shells will have been built before the subgraphs for
* any holes they contain.
*/
subgraphList.Sort();
subgraphList.Reverse();
return subgraphList;
}
/// <summary>
///
/// </summary>
/// <param name="g"></param>
/// <param name="distance"></param>
/// <returns></returns>
public IGeometry Buffer(IGeometry g, double distance)
{
IPrecisionModel precisionModel = workingPrecisionModel;
if (precisionModel == null)
precisionModel = g.PrecisionModel;
// factory must be the same as the one used by the input
geomFact = g.Factory;
OffsetCurveBuilder curveBuilder = new OffsetCurveBuilder(precisionModel, quadrantSegments);
curveBuilder.EndCapStyle = endCapStyle;
OffsetCurveSetBuilder curveSetBuilder = new OffsetCurveSetBuilder(g, distance, curveBuilder);
IList bufferSegStrList = curveSetBuilder.GetCurves();
// short-circuit test
if (bufferSegStrList.Count <= 0)
{
IGeometry emptyGeom = geomFact.CreateGeometryCollection(new IGeometry[0]);
return emptyGeom;
}
ComputeNodedEdges(bufferSegStrList, precisionModel);
graph = new PlanarGraph(new OverlayNodeFactory());
graph.AddEdges(edgeList.Edges);
IList subgraphList = CreateSubgraphs(graph);
PolygonBuilder polyBuilder = new PolygonBuilder(geomFact);
BuildSubgraphs(subgraphList, polyBuilder);
IList resultPolyList = polyBuilder.Polygons;
IGeometry resultGeom = geomFact.BuildGeometry(resultPolyList);
return resultGeom;
}
/// <summary>
///
/// </summary>
/// <returns></returns>
public bool IsInteriorsConnected()
{
// node the edges, in case holes touch the shell
IList splitEdges = new ArrayList();
geomGraph.ComputeSplitEdges(splitEdges);
// form the edges into rings
PlanarGraph graph = new PlanarGraph(new OverlayNodeFactory());
graph.AddEdges(splitEdges);
SetInteriorEdgesInResult(graph);
graph.LinkResultDirectedEdges();
IList edgeRings = BuildEdgeRings(graph.EdgeEnds);
/*
* Mark all the edges for the edgeRings corresponding to the shells
* of the input polygons. Note only ONE ring gets marked for each shell.
*/
VisitShellInteriors((IGeometry) geomGraph.Geometry, graph);
/*
* If there are any unvisited shell edges
* (i.e. a ring which is not a hole and which has the interior
* of the parent area on the RHS)
* this means that one or more holes must have split the interior of the
* polygon into at least two pieces. The polygon is thus invalid.
*/
return !HasUnvisitedShellEdge(edgeRings);
}
/// <summary>
/// Mark all the edges for the edgeRings corresponding to the shells of the input polygons.
/// Only ONE ring gets marked for each shell - if there are others which remain unmarked
/// this indicates a disconnected interior.
/// </summary>
/// <param name="g"></param>
/// <param name="graph"></param>
private void VisitShellInteriors(IGeometry g, PlanarGraph graph)
{
if (g is IPolygon)
{
IPolygon p = (IPolygon) g;
VisitInteriorRing(p.Shell, graph);
}
if (g is IMultiPolygon)
{
IMultiPolygon mp = (IMultiPolygon) g;
foreach (IPolygon p in mp.Geometries)
VisitInteriorRing(p.Shell, graph);
}
}
/// <summary>
///
/// </summary>
/// <param name="ring"></param>
/// <param name="graph"></param>
private void VisitInteriorRing(ILineString ring, PlanarGraph graph)
{
ICoordinate[] pts = ring.Coordinates;
ICoordinate pt0 = pts[0];
/*
* Find first point in coord list different to initial point.
* Need special check since the first point may be repeated.
*/
ICoordinate pt1 = FindDifferentPoint(pts, pt0);
Edge e = graph.FindEdgeInSameDirection(pt0, pt1);
DirectedEdge de = (DirectedEdge) graph.FindEdgeEnd(e);
DirectedEdge intDe = null;
if (de.Label.GetLocation(0, Positions.Right) == Locations.Interior)
intDe = de;
else if (de.Sym.Label.GetLocation(0, Positions.Right) == Locations.Interior)
intDe = de.Sym;
Assert.IsTrue(intDe != null, "unable to find dirEdge with Interior on RHS");
VisitLinkedDirectedEdges(intDe);
}
/// <summary>
///
/// </summary>
/// <param name="graph"></param>
private void SetInteriorEdgesInResult(PlanarGraph graph)
{
foreach (DirectedEdge de in graph.EdgeEnds)
if (de.Label.GetLocation(0, Positions.Right) == Locations.Interior)
de.InResult = true;
}
/// <summary>
/// Add a complete graph.
/// The graph is assumed to contain one or more polygons,
/// possibly with holes.
/// </summary>
/// <param name="graph"></param>
public void Add(PlanarGraph graph)
{
Add(graph.EdgeEnds, graph.Nodes);
}