Change exact area in binary images from 1 to 0

Hello, I have this binary image, I know the center and the radius of that circle, and I would like to change this circle to black so from 1 to 0. My goal is to see only the little line without the circle. How can I do it?

Thank you so much

Answer 1

[Matt J]

load BW

hole = bwareafilt(~BW,1,'smallest') ;

BW=BW& ~imdilate(hole,strel('disk',5));

imshow(BW)

[Eliska Paulikova]

Thank you so much, can I ask what ~ do?

[Matt J]

You're welcome, but please Accept-click the answer if it addresses your question.

The ~ operator is logical complement,

~0, 

ans = logical
   1

~1

ans = logical
   0

[Eliska Paulikova]

Thank you so much