code: function() {
          if (this.degrees === 0) {
              return this.clone();
          }
          var topLeft = this.getTopLeft();
          var topRight = this.getTopRight();
          var bottomLeft = this.getBottomLeft();
          var bottomRight = this.getBottomRight();
          var minX = Math.min(topLeft.x, topRight.x, bottomLeft.x, bottomRight.x);
          var maxX = Math.max(topLeft.x, topRight.x, bottomLeft.x, bottomRight.x);
          var minY = Math.min(topLeft.y, topRight.y, bottomLeft.y, bottomRight.y);
          var maxY = Math.max(topLeft.y, topRight.y, bottomLeft.y, bottomRight.y);
          return new $.Rect(
              minX,
              minY,
              maxX - minX,
              maxY - minY);
      }
docs: Retrieves the smallest horizontal (degrees=0) rectangle which contains
  this rectangle.
  @returns {OpenSeadragon.Rect}