如何在Flutter中的盒子装饰图像上添加不透明的覆盖

import 'package:flutter/material.dart';

Stack(
  children: [
    // 图像
    Image.network('https://example.com/image.jpg'),
    // 不透明的覆盖
    Container(
      color: Colors.black.withOpacity(0.5), // 设置颜色和不透明度
    ),
  ],
)

Stack(
  children: [
    Image.network('https://example.com/image.jpg'),
    Positioned(
      top: 0,
      left: 0,
      width: MediaQuery.of(context).size.width / 2,
      height: MediaQuery.of(context).size.height / 2,
      child: Container(
        color: Colors.black.withOpacity(0.5),
      ),
    ),
  ],
)