toggle(_originalEvent = null) {
    if (this.imageData.ratio === 1) {
      this.zoomTo(this.imageData.oldRatio, true, null, _originalEvent);
    } else {
      this.zoomTo(1, true, null, _originalEvent);
    }

    return this;
  }
Toggle the image size between its current size and natural size
@param {Event} [_originalEvent=null] - The original event if any.
@returns {Viewer} this