overlay_on_image.dart

import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Card(
      clipBehavior: Clip.antiAlias,
      child: Stack(children: [
        Image.network(
            'https://images.pexels.com/photos/7903158/pexels-photo-7903158.jpeg?auto=compress&cs=tinysrgb&dpr=1&w=500'),
        Positioned(
          left: 0,
          right: 0,
          bottom: 0,
          height: 150,
          child: Container(
              color: Colors.black45,
              alignment: Alignment.topRight,
              padding: EdgeInsets.all(8),
              child: Text('HELLO')),
        ),
      ]),
    );
  }
}