Find an almost circular strip of bright pixels in this image.

Question

This is the problem that I have: I have an image as shown below. I want to find a circular area, which I marked with a red line to display here (this is a special bright ring).

Initially this is what I am doing now: (MATLAB)

binaryImage = imdilate(binaryImage,strel('disk',5)); 
binaryImage = imfill(binaryImage, 'holes'); % Fill holes.
binaryImage = bwareaopen(binaryImage, 20000); % Remove small blobs.
binaryImage = imerode(binaryImage,strel('disk',300));
out = binaryImage;
img_display = immultiply(binaryImage,rgb2gray(J1));
figure, imshow(img_display);

The output, apparently, is cut out on one of the parts of the object (for another image as an input, and not for the one shown above). I want the result to be such that it is symmetrical (its not always an ideal circle when it rotates).

I want to strictly avoid im2bw, because as soon as I binarize, I lose a lot of form information.

This is what I was thinking:

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Answer 1

'log'. , , - 2- ( , ), , . , , .

img = im2double(rgb2gray(imread('wheel.png')));
img = imresize(img, 0.25, 'bicubic');

filt_img = imfilter(img, fspecial('log',31,5));
bin_img = filt_img < 0;

subplot(2,2,1);
imshow(filt_img,[]);

% Get regionprops
rp = regionprops(bin_img,'EulerNumber','Eccentricity','Area','PixelIdxList','PixelList'); 
rp = rp([rp.EulerNumber] == 0 & [rp.Eccentricity] < 0.5 & [rp.Area] > 2000);

bin_img(:) = false;
bin_img(vertcat(rp.PixelIdxList)) = true;
subplot(2,2,2);
imshow(bin_img,[]);

bin_img(:) = false;
bin_img(rp(1).PixelIdxList) = true;
bin_img = imfill(bin_img,'holes');

img_new = img;
img_new(~bin_img) = 0;

subplot(2,2,3);
imshow(img_new,[]);

bin_img(:) = false;
bin_img(rp(2).PixelIdxList) = true;
bin_img = imfill(bin_img,'holes');

img_new = img;
img_new(~bin_img) = 0;

subplot(2,2,4);
imshow(img_new,[]);

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