code: function scaleY(_scaleY) {
      var scaleX = this.imageData.scaleX;
      return this.scale(isNumber(scaleX) ? scaleX : 1, _scaleY);
    }
docs: Scale the image on the y-axis.
  @param {number} scaleY - The scale ratio on the y-axis.
  @returns {Cropper} this