CustomClipperBezierCurve.dart

import 'package:flutter/material.dart';

final Color darkBlue = Color(0xffffffff);

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: Stack(children: [
          Padding(
              padding: EdgeInsets.all(20),
              child: ClipPath(
                clipper: MyClipper(),
                child: Container(
                    decoration: BoxDecoration(
                        boxShadow: [
                      BoxShadow(
                        color: Colors.black.withOpacity(.5),
                        spreadRadius: 13,
                        blurRadius: 13.0,
                        offset: Offset(6.0, 7.0),
                      ),
                    ],
                        gradient: LinearGradient(
                          begin: Alignment.topRight,
                          end: Alignment.bottomLeft,
                          //stops: [0.1, 0.5, 0.7, 0.9],
                          colors: [
                            Color(0xFFF9D976),
                            Color(0xFFF39F86),
                           
                          ],
                        ),
                        color: Colors.red)),
              )),
         
           Positioned(
              top: 320,
              child: Padding( 
           padding:EdgeInsets.all(28),
           child: Image.network(
                  "https://upload.wikimedia.org/wikipedia/en/thumb/e/e0/Iron_Man_bleeding_edge.jpg/250px-Iron_Man_bleeding_edge.jpg")))
        ])));
  }
}

class MyClipper extends CustomClipper<Path> {
  @override
  Path getClip(Size size) {
    var path = new Path();

    path.lineTo(0.0, size.height * 0.75);

//     var firstEndPoint = new Offset(size.width / 2, size.height - 40);
//     var firstControlPoint = new Offset(size.width / 4, size.height);
//     path.quadraticBezierTo(firstControlPoint.dx, firstControlPoint.dy,
//         firstEndPoint.dx, firstEndPoint.dy);
//     var secondControlPoint =
//         Offset(size.width - (size.width / 3.25), size.height - 65);
//     var secondEndPoint = Offset(size.width, size.height - 40);
//     path.quadraticBezierTo(secondControlPoint.dx, secondControlPoint.dy,
//         secondEndPoint.dx, secondEndPoint.dy);
//     path.lineTo(size.width, size.height - 40);
//     path.lineTo(size.width, 0.0);

    var firstControlPoint = Offset(size.width / 2, size.height);
    var firstEndPoint = new Offset(size.width, size.height * 0.75);
    path.quadraticBezierTo(firstControlPoint.dx, firstControlPoint.dy,
        firstEndPoint.dx, firstEndPoint.dy);

    path.lineTo(size.width, 0);
    path.close();

    return path;
  }

  @override
  bool shouldReclip(CustomClipper<Path> oldClipper) {
    return false;
  }
}