code: function() {
          var boundingBox = this.getBoundingBox();
          var x = Math.floor(boundingBox.x);
          var y = Math.floor(boundingBox.y);
          var width = Math.ceil(boundingBox.width + boundingBox.x - x);
          var height = Math.ceil(boundingBox.height + boundingBox.y - y);
          return new $.Rect(x, y, width, height);
      }
docs: Retrieves the smallest horizontal (degrees=0) rectangle which contains
  this rectangle and has integers x, y, width and height
  @returns {OpenSeadragon.Rect}