code: function scale(scaleX) {
      var scaleY = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : scaleX;
      var imageData = this.imageData;
  
  
      scaleX = Number(scaleX);
      scaleY = Number(scaleY);
  
      if (this.viewed && !this.played && this.options.scalable) {
        var changed = false;
  
        if (isNumber(scaleX)) {
          imageData.scaleX = scaleX;
          changed = true;
        }
  
        if (isNumber(scaleY)) {
          imageData.scaleY = scaleY;
          changed = true;
        }
  
        if (changed) {
          this.renderImage();
        }
      }
  
      return this;
    }
docs: Scale the image.
  @param {number} scaleX - The scale ratio on the x-axis.
  @param {number} [scaleY=scaleX] - The scale ratio on the y-axis.
  @returns {Viewer} this