how to find the centre point of a circle?

A dent has been found on the outer edge of the circle. how to find the angle between the center point and the dent region?

Answer 1

[Image Analyst]

Like I said in your related question, find the dents

dentsImage = bwconvhull(binaryImage) - binaryImage;

Then get the centroids

measurements = regionprops(binaryImage, 'Centroid');

which I'm sure you already know how to do because you've used regionprops many, many times in the past.