getImage() {
    if (this.zoomifyImage_) {
      return this.zoomifyImage_;
    }
    const image = super.getImage();
    if (this.state == TileState.LOADED) {
      const tileSize = this.tileSize_;
      if (image.width == tileSize[0] && image.height == tileSize[1]) {
        this.zoomifyImage_ = image;
        return image;
      }
      const context = createCanvasContext2D(tileSize[0], tileSize[1]);
      context.drawImage(image, 0, 0);
      this.zoomifyImage_ = context.canvas;
      return context.canvas;
    }
    return image;
  }
Get the image element for this tile.
@return {HTMLCanvasElement|HTMLImageElement|HTMLVideoElement} Image.
@override