Finding circle in an image

Hi guys. I have an image ( attached ) and I'm trying to find the location of the centre of the hole ( circle ) that is apparent in that image. I've been using imfindcircles ( tried different sensitivities ) with no success, probably due to that light reflection ( ? ) that is visible in the hole. Can anyone propose how to resolve that issue ? Thank you.

Answer 1

[Image Analyst]

I'd try to zero out the bright stuff, then threshold and call regionprops() and compute the circularity. Here's a start:

mask = grayImage > 200;
grayImage(mask) = 0;
binaryImage = grayImage < 50; % or whatever works.
labeledImage = bwlabel(binaryImage);
props = regionprops(labeledImage, 'Area', 'Perimeter');
allAreas = [props.Area];
allPerims = [props.Perimeter];
circularities = allPerimeters .^ 2 ./ (4 * pi * allAreas);
roundBlobIndexes = find(circularities < 2);
roundBlobs = ismember(labeledImage, roundBlobIndexes);
imshow(roundBlobs);