///<summary>
/// Gets the union of the input geometries.
/// If no input geometries were provided, a POINT EMPTY is returned.
///</summary>
///<returns>a Geometry containing the union</returns>
/// <returns>an empty GEOMETRYCOLLECTION if no geometries were provided in the input</returns>
public IGeometry Union()
{
if (_geomFact == null)
{
return(null);
}
IGeometry unionPoints = null;
if (_points.Count > 0)
{
IGeometry ptGeom =
_geomFact.BuildGeometry(convertPoints(_points).ToList());
unionPoints = UnionNoOpt(ptGeom);
}
IGeometry unionLines = null;
if (_lines.Count > 0)
{
IGeometry lineGeom = _geomFact.BuildGeometry(convertLineStrings(_lines).ToList());
unionLines = UnionNoOpt(lineGeom);
}
IGeometry unionPolygons = null;
if (_polygons.Count > 0)
{
unionPolygons = CascadedPolygonUnion.Union(_polygons);
}
/**
* Performing two unions is somewhat inefficient,
* but is mitigated by unioning lines and points first
*/
IGeometry unionLA = UnionWithNull(unionLines, unionPolygons);
IGeometry union = null;
if (unionPoints == null)
{
union = unionLA;
}
else if (unionLA == null)
{
union = unionPoints;
}
else
{
union = PointGeometryUnion.Union((IPoint)unionPoints, unionLA);
}
if (union == null)
{
return(_geomFact.CreateGeometryCollection(null));
}
return(union);
}
public static IGeometry Union(ICollection polys)
{
var op = new CascadedPolygonUnion(polys);
return(op.Union());
}
public static IGeometry Union(ICollection polys)
{
var op = new CascadedPolygonUnion(polys);
return op.Union();
}