code: function( viewerX, viewerY, current ) {
          var scale = (current ? this._scaleSpring.current.value : this._scaleSpring.target.value);
          return new $.Point(viewerX * (this.source.dimensions.x / scale),
              viewerY * ((this.source.dimensions.y * this.contentAspectX) / scale));
      }
docs: private