How detect spot white circle on image

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I would like detect spot white are like below image . Hope anyone help . Thanks!

Accepted Answer

KSSV
KSSV on 6 Jun 2017
Edited: KSSV on 6 Jun 2017
I = imread('Screen Shot 2017-06-06 at 3.54.58 PM.png') ;
im = imclearborder(im2bw(I));
im_fill = imfill(im, 'holes');
s = regionprops(im_fill, 'Area', 'PixelList');
[~,ind] = max([s.Area]);
pix = sub2ind(size(im), s(ind).PixelList(:,2), s(ind).PixelList(:,1));
out = zeros(size(im));
out(pix) = im(pix);
% imshow(out);
[y,x] = find(out) ;
idx = boundary(x,y) ;
% idx = convhull(x,y) ;
imshow(I)
hold on
plot(x(idx),y(idx),'r','linewidth',3)
If boundary doesn't work, use convexhull

More Answers (1)

Image Analyst
Image Analyst on 6 Jun 2017
KSSV's code finds the largest blob that is not touching the border, whereas you actually want roundish objects.
Like I said in your duplicate post, You could use my code for circularity. Or you could also look for Solidities close to 1, or get the BoundingBox and look for aspect ratios close to 1.

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