zoom(ratio, showTooltip = false, pivot = null, _originalEvent = null) {
    const { imageData } = this;

    ratio = Number(ratio);

    if (ratio < 0) {
      ratio = 1 / (1 - ratio);
    } else {
      ratio = 1 + ratio;
    }

    this.zoomTo(
      (imageData.width * ratio) / imageData.naturalWidth,
      showTooltip,
      pivot,
      _originalEvent,
    );

    return this;
  }
Zoom the image with a relative ratio.
@param {number} ratio - The target ratio.
@param {boolean} [showTooltip=false] - Indicates whether to show the tooltip.
@param {Object} [pivot] - The pivot point coordinate for zooming.
@param {Event} [_originalEvent=null] - The original event if any.
@returns {Viewer} this