/// <summary>
/// Convert a self intersecting polygon into simple polygons
/// </summary>
/// <param name="poly"></param>
/// <param name="fillType"></param>
/// <returns></returns>
public static List<List<IntPoint>> SimplifyPolygon(List<IntPoint> poly, PolyFillType fillType = PolyFillType.EvenOdd)
{
Contract.Requires(poly != null);
Contract.Ensures(Contract.Result<List<List<IntPoint>>>() != null);
var result = new List<List<IntPoint>>();
var c = new Clipper { ForceSimple = true };
c.AddPolygon(poly, PolyType.Subject);
c.Execute(ClipType.Union, result, fillType, fillType);
return result;
}
private PolyOffsetBuilder(IReadOnlyList<IReadOnlyList<IntPoint>> points, List<List<IntPoint>> solution, bool isPolygon, double delta, JoinType jointype, EndType endtype, double limit = 0)
{
Contract.Requires(points != null);
Contract.Requires(solution != null);
if (ReferenceEquals(solution, points))
throw new ArgumentException("Input and Output parameters cannot be the same", nameof(solution));
if (delta == 0)
return;
_p = points;
_delta = delta;
_rmin = 0.5;
if (jointype == JoinType.Miter)
{
if (limit > 2)
_rmin = 2.0 / (limit * limit);
limit = 0.25; //just in case endtype == etRound
}
else
{
if (limit <= 0)
limit = 0.25;
else if (limit > Math.Abs(delta))
limit = Math.Abs(delta);
}
solution.Clear();
for (_i = 0; _i < points.Count; _i++)
{
var len = points[_i].Count;
if (len == 0 || (len < 3 && delta <= 0))
continue;
else if (len == 1)
{
_currentPoly = new List<IntPoint>();
_currentPoly = InternalHelpers.BuildArc(points[_i][0], 0, 2 * Math.PI, delta, limit);
solution.Add(_currentPoly);
continue;
}
var forceClose = points[_i][0].Equals(points[_i][len - 1]);
if (forceClose)
len--;
//build normals ...
_normals.Clear();
for (var j = 0; j < len - 1; ++j)
_normals.Add(points[_i][j].UnitNormal(points[_i][j + 1]));
if (isPolygon || forceClose)
_normals.Add(points[_i][len - 1].UnitNormal(points[_i][0]));
else
_normals.Add(_normals[len - 2]);
_currentPoly = new List<IntPoint>();
if (isPolygon || forceClose)
{
_k = len - 1;
for (_j = 0; _j < len; ++_j)
OffsetPoint(jointype, limit);
solution.Add(_currentPoly);
if (!isPolygon)
{
_currentPoly = new List<IntPoint>();
_delta = -_delta;
_k = len - 1;
for (_j = 0; _j < len; ++_j)
OffsetPoint(jointype, limit);
_delta = -_delta;
_currentPoly.Reverse();
solution.Add(_currentPoly);
}
}
else
{
_k = 0;
for (_j = 1; _j < len - 1; ++_j)
OffsetPoint(jointype, limit);
IntPoint pt1;
if (endtype == EndType.OpenButt)
{
_j = len - 1;
pt1 = new IntPoint(InternalHelpers.Round(points[_i][_j].X + _normals[_j].X * delta), InternalHelpers.Round(points[_i][_j].Y + _normals[_j].Y * delta));
AddPoint(pt1);
pt1 = new IntPoint(InternalHelpers.Round(points[_i][_j].X - _normals[_j].X * delta), InternalHelpers.Round(points[_i][_j].Y - _normals[_j].Y * delta));
AddPoint(pt1);
}
else
{
_j = len - 1;
_k = len - 2;
_normals[_j] = new DoublePoint(-_normals[_j].X, -_normals[_j].Y);
if (endtype == EndType.OpenSquare)
DoSquare();
else
DoRound(limit);
}
//re-build Normals ...
for (var j = len - 1; j > 0; j--)
{
_normals[_j] = new DoublePoint(-_normals[j - 1].X, -_normals[j - 1].Y);
}
_normals[0] = new DoublePoint(-_normals[1].X, -_normals[1].Y);
_k = len - 1;
for (_j = _k - 1; _j > 0; --_j)
OffsetPoint(jointype, limit);
if (endtype == EndType.OpenButt)
{
pt1 = new IntPoint(InternalHelpers.Round(points[_i][0].X - _normals[0].X * delta), InternalHelpers.Round(points[_i][0].Y - _normals[0].Y * delta));
AddPoint(pt1);
pt1 = new IntPoint(InternalHelpers.Round(points[_i][0].X + _normals[0].X * delta), InternalHelpers.Round(points[_i][0].Y + _normals[0].Y * delta));
AddPoint(pt1);
}
else
{
_k = 1;
if (endtype == EndType.OpenSquare)
DoSquare();
else
DoRound(limit);
}
solution.Add(_currentPoly);
}
}
//finally, clean up untidy corners ...
var clpr = new Clipper();
clpr.AddPolygons(solution, PolyType.Subject);
if (delta > 0)
{
clpr.Execute(ClipType.Union, solution, PolyFillType.Positive, PolyFillType.Positive);
}
else
{
var r = clpr.GetBounds();
var outer = new List<IntPoint>(4) {
new IntPoint(r.Left - 10, r.Bottom + 10),
new IntPoint(r.Right + 10, r.Bottom + 10),
new IntPoint(r.Right + 10, r.Top - 10),
new IntPoint(r.Left - 10, r.Top - 10)
};
clpr.AddPolygon(outer, PolyType.Subject);
clpr.ReverseSolution = true;
clpr.Execute(ClipType.Union, solution, PolyFillType.Negative, PolyFillType.Negative);
if (solution.Count > 0)
solution.RemoveAt(0);
}
}