Full blurring of the container instead of a circle – Flutter

I want to have only one blurred circle but this is not possible and the outer parts of the circle i.e. Container are completely blurred. The same is true for CustomPoint.

Codes :

Center(
    child: Stack(alignment: Alignment.center, children: [
      Image.network(
          "https://mojekooh.com/wp-content/uploads/2020/09/1024px-Matterhorn_from_Domh%C3%BCtte_-_2.jpg"),
      ClipRRect(
        child: BackdropFilter(
          filter: ImageFilter.blur(sigmaX: 5, sigmaY: 5),
          child: Container(
            width: 200,
            height: 100,
            decoration: const BoxDecoration(
                color: Color.fromARGB(33, 255, 0, 0),
                shape: BoxShape.circle),
          ),
        ),
      )
    ]),
  ),

I searched the internet and did not find anything

Update:

My friends, I solved this problem:

    Stack(alignment: Alignment.center, children: [
        Image.network(
            "https://mojekooh.com/wp-content/uploads/2020/09/1024px-Matterhorn_from_Domh%C3%BCtte_-_2.jpg"),
        ClipOval(
         clipper: CoustomCircle(),
          child: BackdropFilter(
           filter: ImageFilter.blur(sigmaX: 5, sigmaY: 5),
            child: Container(
              width: 200,
              height: 200,
              decoration: const BoxDecoration(
                  color: Color.fromARGB(57, 255, 0, 0),
                  shape: BoxShape.circle),
            ),
          ),
        )
      ]),


class CoustomCircle extends CustomClipper<Rect> {

  @override
  Rect getClip(size){
    return const Rect.fromLTWH(0, 0, 200, 200);
  }

@override
  bool shouldReclip(oldClipper){
  return true;
}
}