Paste each of these expressions into your anchor point property:
// [CENTER, CENTER]
l = thisLayer.sourceRectAtTime();[l.left + l.width/2, l.top + l.height/2];
// [LEFT, CENTER]
I = thisLayer.sourceRectAtTime();[l.left, l.top + l.height/2];
// [LEFT, BOTTOM]
l = thisLayer.sourceRectAtTime();[l.left, l.top + l.height];
// [RIGHT, BOTTOM]
l = thisLayer.sourceRectAtTime();[l.left + l.width, l.top + l.height];
// [RIGHT, TOP]
l = thisLayer.sourceRectAtTime();[l.left + l.width, l.top];
// [CENTER, TOP]
l = thisLayer.sourceRectAtTime();[l.left + l.width/2, l.top];
// [CENTER, BOTTOM]
l = thisLayer.sourceRectAtTime();[l.left + l.width/2, l.top + l.height];