shadowImage() Coordinates Have no Effect

[jmorfis]

->shadowImage() seems broken.

The x, y coordinates do not have any affect. The shadow coordinates appear to be fixed slightly to the bottom-right as you increase the sigma. But the x,y (parameters 3,4) do nothing.

These two yield the same exact results:
$shadow->shadowImage( 100, 2, 0, 0 );
$shadow->shadowImage( 100, 2, 100, 100);