Copy visible pixels of 2 Sprites

Peepz,

I want to copy the visible pixels of 2 sprites whitin a new Sprite.
The top Sprite is transparent in the middle so i have to see the sprite beneath it.
But the middle is always white and not transparent can somebody help?


function cloneBitmap(myOldClip:Sprite, myNewClip:Sprite):void
{
 var myBitmapData:BitmapData = new BitmapData(myOldClip.width - 1, myOldClip.height - 1, true);
 myBitmapData.draw(myOldClip) 
 
 var bmp:Bitmap = new Bitmap(myBitmapData); 
 myNewClip.addChild(bmp);
}