hello, I found the solution.
In graphics I changed the
CompositingMode that determines when to paint a polygon on the other it is overwritten and not superimposed.
Bitmap img = new Bitmap( 200, 200 );
Graphics imgGraph = Graphics.FromImage( img );
imgGraph.CompositingMode = System.Drawing.Drawing2D.CompositingMode.SourceCopy;
imgGraph.FillPolygon( Brushes.Red, Points1 );
imgGraph.FillPolygon( Brushes.Transparent, Points2 );
That's all folks!