/// <summary>
/// Constructs the geometric difference between this Polygon and the supplied Polygons.
/// </summary>
/// <param name="difPolys">The list of intersecting Polygons.</param>
/// <returns>
/// Returns a list of Polygons representing the subtraction of the supplied Polygons from this Polygon.
/// Returns null if the area of this Polygon is entirely subtracted.
/// Returns a list containing a representation of the perimeter of this Polygon if the two Polygons do not intersect.
/// </returns>
public IList <Polygon> Difference(IList <Polygon> difPolys)
{
var thisPath = this.ToClipperPath();
var polyPaths = new List <List <IntPoint> >();
foreach (Polygon polygon in difPolys)
{
polyPaths.Add(polygon.ToClipperPath());
}
Clipper clipper = new Clipper();
clipper.AddPath(thisPath, PolyType.ptSubject, true);
clipper.AddPaths(polyPaths, PolyType.ptClip, true);
var solution = new List <List <IntPoint> >();
clipper.Execute(ClipType.ctDifference, solution);
if (solution.Count == 0)
{
return(null);
}
var polygons = new List <Polygon>();
foreach (List <IntPoint> path in solution)
{
polygons.Add(PolygonExtensions.ToPolygon(path.Distinct().ToList()));
}
return(polygons);
}
/// <summary>
/// Returns Polygons representing the symmetric difference between this Polygon and the supplied Polygon.
/// </summary>
/// <param name="polygon">The intersecting polygon.</param>
/// <returns>
/// Returns a list of Polygons representing the symmetric difference of this Polygon and the supplied Polygon.
/// Returns a representation of this Polygon and the supplied Polygon if the Polygons do not intersect.
/// </returns>
public IList <Polygon> XOR(Polygon polygon)
{
var thisPath = this.ToClipperPath();
var polyPath = polygon.ToClipperPath();
Clipper clipper = new Clipper();
clipper.AddPath(thisPath, PolyType.ptSubject, true);
clipper.AddPath(polyPath, PolyType.ptClip, true);
var solution = new List <List <IntPoint> >();
clipper.Execute(ClipType.ctUnion, solution);
var polygons = new List <Polygon>();
foreach (List <IntPoint> path in solution)
{
polygons.Add(PolygonExtensions.ToPolygon(path));
}
return(polygons);
}