我需要在 Firestore 中添加签名图片的路径作为 URL，但我无法弄清楚这个签名图片的路径。我不想将图像保存到图库中，而是直接保存到 firebase，我该怎么做？也许将它暂时存储在某个地方，直到我将它发送到 firebase。或者我可以将字节保存到 Firebase 并取回图像吗？我是 Flutter 新手，请帮忙。

这是我目前使用的代码：

import 'package:flutter/material.dart';

import 'package:signature/signature.dart';
import 'RegistrationPage.dart';
import 'dart:io';


class signaturePage extends StatefulWidget {

  @override
  _signaturePageState createState() => _signaturePageState();
}

class _signaturePageState extends State<signaturePage> {
  SignatureController controller;
  File imageFile;
 
  @override
  void initState() {
    super.initState();
    controller = SignatureController(
      penColor: Colors.white,penStrokeWidth: 5,);
  }
  @override
  void dispose() {
    super.dispose();
    controller.dispose();
  }
  @override
  Widget build(BuildContext context) => Scaffold(
    body: Column(
      children: [
        Signature(controller: controller,backgroundColor: Colors.black,),Spacer(),buildButtons(context),],)
  );

Widget buildButtons (BuildContext context) => Container(
  color: Colors.black,child: Row(
    mainAxisAlignment: MainAxisAlignment.center,children: [
      buildCheck(context),buildClear(context),);

Widget buildCheck(BuildContext context) => IconButton(
  iconSize: 36,icon: Icon(Icons.check,color: Colors.green),onpressed: () async{
    if(controller.isnotEmpty){
      final signature = await exportSignature();
//print(imageFile);

      // await Navigator.push(context,MaterialPageRoute(
      //     builder: (context) => RegistrationScreen(file: signature)));
    }
  },);

Widget buildClear(BuildContext context) => IconButton(
  iconSize: 36,icon: Icon(Icons.close,color: Colors.red),onpressed: () => controller.clear(),);

Future exportSignature() async {
  final exportController = SignatureController(
    penStrokeWidth: 5,penColor: Colors.black,exportBackgroundColor: Colors.white,points: controller.points,);
  final signature = exportController.toImage();
  

  exportController.dispose();
  return signature;

}
}