onViewed = function onViewed() {
      var imageData = _this2.imageData;
      var render = Array.isArray(options.title) ? options.title[1] : options.title;
      title.innerHTML = escapeHTMLEntities(isFunction(render) ? render.call(_this2, image, imageData) : "".concat(alt, " (").concat(imageData.naturalWidth, " \xD7 ").concat(imageData.naturalHeight, ")"));
    }
View one of the images with image's index
@param {number} index - The index of the image to view.
@returns {Viewer} this