var mask = new ludo.canvas.Mask({ id : 'Mask' });
 canvas.adoptDef(mask); // canvas is a ludo.canvas.Canvas object

 var gr = new ludo.canvas.Gradient({
     id:'gradient'
 });
 gr.addStop('0%', 'white', 0);
 gr.addStop('100%', 'white', 1);
 canvas.adopt(gr);

 var rect2 = new ludo.canvas.Rect({ x:0,y:0, width:500,height:500, fill:gr });
 mask.adopt(rect2); // Append rect to mask
 // create ellipsis with reference to mask
 var ellipse = new ludo.canvas.Ellipse({ cx:100, cy:125, rx:50, ry:70,mask:mask });