Flash - How To Modify Image Dynamically

I'm trying to modify my bitmap to change their pixels to a random color. This is the way I do it (I'm using the FlashPunk library):
private var _v:Point = new Point;
private var _speed:Point = new Point(200, 200);
private var _bmpData:BitmapData = new BitmapData(24, 24, false, 0x000000)
private var _bmpImage:Image = new Image(_bmpData);
public function Player(p:Point) {
[Code] .....

So ok, the function that does this is render(), but in the line
graphic = new Image(_bmpData);
I get new memory for graphic, and this translate into a memory leak in the game. Here is an image of this:
And as you can see, the MEM: part is constantly increasing.