public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { List <System.Windows.Point> Points = new List <System.Windows.Point>(); if (value != null) { ConvexPolygon polygon = value as ConvexPolygon; var centerP = Transformer.ConvertToScreen(polygon.Center()); foreach (Point p in polygon.Points) { var p1 = Transformer.ConvertToScreen(p); Points.Add(new System.Windows.Point(p1.X - centerP.X, p1.Y - centerP.Y)); } return(new PointCollection(Points)); } else { return(null); } }