Comment décorer le conteneur en flottement

Container(
  decoration: BoxDecoration(
    color: const Color(0xff7c94b6),
    image: const DecorationImage(
      image: NetworkImage('https://flutter.github.io/assets-for-api-docs/assets/widgets/owl-2.jpg'),
      fit: BoxFit.cover,
    ),
    border: Border.all(
      color: Colors.black,
      width: 8,
    ),
    borderRadius: BorderRadius.circular(12),
      
 //   borderRadius: new BorderRadius.only(            
 //              topLeft   : const Radius.circular(40.0),
 // 				topRight  : const Radius.circular(40.0),
 //				bottomLeft: const Radius.circular(40.0),
 //			bottomRight:const Radius.circular(40.0),            
 //            )
  ),
)
mohamed mostafa