How to radius image in stack in flutter

i want to radius image in stack can anyone help me please :

this is part of my code :

InkWell(
       

   child: Stack(
              children: <Widget>[
                new Image.asset('assets/Images/b.jpg',fit: BoxFit.cover,),
                Center(child: Text("something",textAlign: TextAlign.center,)),
              ]
          ),
          onTap: () {
            ListOfEpisode();
            print("am");
          },
        ),

radius like this :

try using container decoration.

 InkWell(
                    child: Stack(children: <Widget>[
                      Container(
                        height: 200,
                        width: 200,
                        decoration: BoxDecoration(
                            borderRadius: BorderRadius.circular(40),
                            image: DecorationImage(
                              image: AssetImage(
                                'assets/Images/b.jpg',
                              ),
                              fit: BoxFit.cover,
                            )),
                        child: Center(
                          child: Text(
                            "something",
                            textAlign: TextAlign.center,
                          ),
                        ),
                      ),
                    ]),
                    onTap: () {
                      // ListOfEpisode();
                      // print("am");
                    },
                  ),