problem with copyPixels?

[LewxX²]

I want to make something like an water reflection,
but I have one problem.

copy picture to the right works perfect: (snag-0101.jpg)

object.bitmapData.copyPixels (blubit.bitmapData, new Rectangle(0,0,stage.stageWidth, stage.stageHeight), new Point(1,1))

but I can't copy them to left : (snag-0101.jpg)

object.bitmapData.copyPixels (blubit.bitmapData, new Rectangle(0,0,stage.stageWidth, stage.stageHeight), new Point(-1,1))

=> this doesn't work

how can use the copyPixels method to copy pixels to the left.
negative values doesn't work