void alignPivot([HorizontalAlign hAlign = HorizontalAlign.Center, VerticalAlign vAlign = VerticalAlign.Center ])

Aligns the display object's pivot point relative to the current bounds.

Source 

void alignPivot([
  HorizontalAlign hAlign = HorizontalAlign.Center,
  VerticalAlign vAlign = VerticalAlign.Center]) {

  var b = this.bounds;
  if (hAlign == HorizontalAlign.Left) this.pivotX = b.left;
  if (hAlign == HorizontalAlign.Center) this.pivotX = b.left + b.width / 2;
  if (hAlign == HorizontalAlign.Right) this.pivotX = b.right;
  if (vAlign == VerticalAlign.Top) this.pivotY = b.top;
  if (vAlign == VerticalAlign.Center) this.pivotY = b.top + b.height / 2;
  if (vAlign == VerticalAlign.Bottom) this.pivotY = b.bottom;
}