resize from center of canvas

I have searched and searched but cant seem to find the answer. 

I have an photoshop file that is comprised of a few layers.  I need to resize all the layers so that the object is smaller.  I am using the following line of code and it does the trick, but the layers no longer align.  It appears that the anchorPosition.MiddleCenter uses the extents of the pixels on a particular layer.  I need the item to be resized using the canvas center so that when all the layers are resized, they stack on top of one another.   How do i set the anchor point to use canvas center?

activeDocument.activeLayer.resize(23,23, AnchorPosition.MIDDLECENTER);