Concentric offset on polygon

Question

I am using the Angus Johnson's Clipper Library in .NET/C# and I would like to do several concentric offset on a Polygon with the ClipperOffset class. (http://www.angusj.com/delphi/clipper/documentation/Docs/Units/ClipperLib/Classes/ClipperOffset/_Body.htm).

I want to fill my polygon like the kangaroo (from Angus Johnson's Homepage).

I have written a function to do that, but it needs a big calculation time if I call it 10 times for example :

    static public Polygon doOffset(Polygon p, double offset_nm)
    {
        // Offset to grow up the forbidden polygon
        Polygons solution = new Polygons();
        ClipperOffset co = new ClipperOffset();
        co.AddPath(p, JoinType.jtRound, EndType.etClosedPolygon);
        co.Execute(ref solution, offset_nm);

        return solution[0];
    }

Do you know a more efficient way to do that ? Thanks.

Kangaroo