toDataURL(options) {
    return this._graphics.toDataURL(options);
  }
Get data url
@param {Object} options - options for toDataURL
  @param {String} [options.format=png] The format of the output image. Either "jpeg" or "png"
  @param {Number} [options.quality=1] Quality level (0..1). Only used for jpeg.
  @param {Number} [options.multiplier=1] Multiplier to scale by
  @param {Number} [options.left] Cropping left offset. Introduced in fabric v1.2.14
  @param {Number} [options.top] Cropping top offset. Introduced in fabric v1.2.14
  @param {Number} [options.width] Cropping width. Introduced in fabric v1.2.14
  @param {Number} [options.height] Cropping height. Introduced in fabric v1.2.14
@returns {string} A DOMString containing the requested data URI
@example
imgEl.src = imageEditor.toDataURL();

imageEditor.loadImageFromURL(imageEditor.toDataURL(), 'FilterImage').then(() => {
     imageEditor.addImageObject(imgUrl);
});