public onFileChange(files: FileUpload | FileUpload[]): void {
    if (files == null) {
      return;
    }
    const canvasElement = this.canvas.getElement();
    const width = canvasElement.clientWidth;
    const height = canvasElement.clientHeight;

    const chosenFile: FileUpload = Array.isArray(files) ? files[0] : files as FileUpload;
    const uploadedFile = chosenFile.data;
    const reader = new FileReader();
    reader.onload = (e) => {
      const imageUrl = e.target?.result as string;
      fabric.FabricImage.fromURL(imageUrl).then((img) => {
        img.set({ left: 0, top: 0 }).scaleToWidth(width);
        img.canvas = this.canvas
        this.canvas.backgroundImage = img;
        this.canvas.renderAll();
      });
    };
    reader.readAsDataURL(uploadedFile);
  }