load(imageName, img) {
    let promise;

    if (!imageName && !img) {
      // Back to the initial state, not error.
      const canvas = this.getCanvas();

      canvas.backgroundImage = null;
      canvas.renderAll();

      promise = new Promise((resolve) => {
        this.setCanvasImage('', null);
        resolve();
      });
    } else {
      promise = this._setBackgroundImage(img).then((oImage) => {
        this.setCanvasImage(imageName, oImage);
        this.adjustCanvasDimension();

        return oImage;
      });
    }

    return promise;
  }
Load image from url
@param {?string} imageName - File name
@param {?(fabric.Image|string)} img - fabric.Image instance or URL of an image
@returns {Promise}