Getting square magnifying filter, even though it's defined by a circular object.

Question

So I have created a magnifying effect in AS3 where the BitmapData collected is filtered through a shape that is circular.
However, when I test this out, the distortion filter goes beyond the object's circular bounds and creates a square.
When I go to mask the BitmapData, it says I cannot mask it.
Problem:                                                                       
Image Without:
I just need the best method to make this BitmapData circular.
My code:
(the premise of this is, to have a ball tthat your drag and tracks the speed of throw to reflect bouncing speed on stage, while it bounces it magnifies an image, or can be dragged to magnify it)
//Magnifying://
var dPoint:Point = new Point(0, 0);
var dMap:BitmapData = new BitmapData(object.width, object.height, true, 0x808080)
dMap.draw(colorMap_mc)
removeChild(colorMap_mc)
var dFilter:DisplacementMapFilter = new DisplacementMapFilter ();
dFilter.scaleX         = 30   
dFilter.scaleY         = 30   
dFilter.componentX     = 1           
dFilter.componentY     = 2           
dFilter.mode        = "color"   
dFilter.color        = 0x000000   
dFilter.alpha         = 0           
dFilter.mapPoint    = dPoint;   
dFilter.mapBitmap    = dMap;       
Image_mc.filters = [dFilter]
Image_mc.addEventListener(Event.ENTER_FRAME, onFrame)
function onFrame(e:Event){
    dPoint.x += ((object.x-colorMap_mc.width/2)-dPoint.x)
    dPoint.y += ((object.y-colorMap_mc.height/2)-dPoint.y)
    object.x += xSpeed;
    object.y += ySpeed;
    dFilter.mapPoint = dPoint
    Image_mc.filters = [dFilter]
Both my colormap_mc and object are round and exactly the same size.
The square is the dimensions of the circular object, but alas, it's still a square.

Answer 1

Yeah, but at further staring, I notice that the square doesnt have the magnifying filter.
So the displacement's location doesn't seem to be the issue.  :-/