How to crop the internal area of a contour?

Question

I am working on Retinal fundus images.The image consists of a circular retina on a black background. With OpenCV, I have managed to get a contour which surrounds the whole c

Answer 1

Expansion of nathancy's answer -

You can use any of Contour feature like Bounding Rectangle, Minimum enclosing circle, Fit Ellipse etc. More details here.