Flutter Image ambient backlight

main.dart

// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:flutter/material.dart';
import 'dart:ui';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

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

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
  

    return Scaffold(
        appBar: AppBar(
          title: Text("Image ambient backlight"),
        ),
        body: Center(
            child: Column(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
              ImageColoredShadow(),
              Center(child: Text("This is a caption"))
            ])));
  }
}

class ImageColoredShadow extends StatelessWidget {
  
  @override
  Widget build(BuildContext context) {
    
    double _size = 200.0;
    double blurRadius = 20.0;
    double blurSigma = 7.0;
    String imageUrl = 'https://mp-prod-de-medialib.s3-eu-central-1.amazonaws.com/motivwelt/stockimage/buntes-laub/overview/buntes-laub-l.jpg';
    
    return Stack(children: [
                Center(
                    child: ClipRRect(
                        child: BackdropFilter(
                            filter: ImageFilter.blur(sigmaX: 10, sigmaY: 10),
                            child: new Container(
                              width: _size + blurRadius,
                              height: _size + blurRadius,
                              decoration: new BoxDecoration(
                                  shape: BoxShape.circle,
                                  image: new DecorationImage(
                                      fit: BoxFit.cover,
                                      image: new NetworkImage(imageUrl))),
                            )))),
                Positioned.fill(
                    child: BackdropFilter(
                        filter: ImageFilter.blur(
                            sigmaX: blurSigma, sigmaY: blurSigma),
                        child: Container(color: Colors.black.withOpacity(0)))),
                Positioned.fill(
                  child: Center(
                    child: new Container(
                        width: _size,
                        height: _size,
                        decoration: new BoxDecoration(
                            shape: BoxShape.circle,
                            image: new DecorationImage(
                                fit: BoxFit.cover,
                                image: new NetworkImage(imageUrl)))),
                  ),
                )
              ]);
  }
}