public override Point[] GetPoints(Size size, double thickness)
{
var alpha = size.FitRectangle(thickness);
return new[]
{
new Point(thickness*Math.Sin(alpha), 0),
new Point(0, thickness*Math.Cos(alpha)),
new Point(size.Width - thickness*Math.Sin(alpha), size.Height),
new Point(size.Width, size.Height - thickness*Math.Cos(alpha))
};
}