MATLAB: I tried to find inner and outer diameter of an circle using this code but it didn’t give me outputs images like below I’ve attached

image processing

Here is the code % Read your image and binarize it I = imread('C:\Users\Rangika Mark\Desktop\WP_20171207_11_47_46_Selfie.jpg'); Igray = rgb2gray(I); BW = imbinarize(Igray); % Measure the outer radius BWout = ~BW; BWout = imfill(BWout,'holes'); statOuter = regionprops(BWout,{'EquivDiameter','Centroid'}); outerRadius = statOuter.EquivDiameter/2; % Measure the inner radius BWin = imclearborder(BW); BWin = imopen(BWin, strel('disk',5)); % Remove noise statInner = regionprops(BWin,{'EquivDiameter','Centroid'}) innerRadius = statInner.EquivDiameter/2; % Show the result figure imshow(I) hold on viscircles(statOuter.Centroid, outerRadius,'Color','r') viscircles(statInner.Centroid, innerRadius,'Color','r')

Best Answer

In this case, you should pick up the region, that has maximum diameter, from the output of regionprops function. Based on your original code, I have slightly modified to do that.
I = imread('8122bCXHqPL._SY463_.jpg');
Igray = rgb2gray(I);
BW = imbinarize(Igray); 
% Measure the outer radius 
BWout = ~BW; 
BWout = imfill(BWout,'holes');
statOuter = struct2table(regionprops(BWout,{'MajorAxisLength','Centroid'}));
[~,idxOuter] = max(statOuter.MajorAxisLength);
outerRadius = statOuter.MajorAxisLength(idxOuter)/2; 
% Measure the inner radius 
BWin = imclearborder(BW); 
BWin = imopen(BWin, strel('disk',5)); 
statInner = struct2table(regionprops(BWin,{'MajorAxisLength','Centroid'}));
[~,idxInner] = max(statInner.MajorAxisLength);
innerRadius = statInner.MajorAxisLength(idxInner)/2; 
% Show the result 
figure
imshow(I) 
hold on 
viscircles(statOuter.Centroid(idxOuter,:), outerRadius,'Color','r') 
viscircles(statInner.Centroid(idxInner,:), innerRadius,'Color','r')
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