title: How to fill up a drawable image
body: <p>I have a .png image as seen below. I want to draw an inner circle inside the colorful ring so that it fills the white-space completely. Is there a way for me to calculate how large the radius of the inner circle should be without hard-coding values?
  <a href="https://i.stack.imgur.com/1Zlfe.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/1Zlfe.png" alt="enter image description here" /></a></p>