bmd = document.getElementById("canvas").bitmapData;

bikes = new Image();
bikes.src = "res/bikes.png";
bmd.draw(bikes);

lenna = new Image();
lenna.src = "res/lenna-300x300.png";
leenaData = new BitmapData(300, 300);
leenaData.draw(lenna);

bmd.copyChannel(leenaData, 
	new Rectangle(50, 50, 200, 200), 
	new Point(50, 50), 
	BitmapDataChannel.GREEN, 
	BitmapDataChannel.GREEN);