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How to find minimum distance between two cylindrical objects from binary image?

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Hello,
I have this binary image
in which I have two cylindrical objects and I want to find out the minimum distance between these. How to do that? I have read this answer but I cannot understand this. Can anyone help to calculate minimum distance in a more simple way? Thanks.

Accepted Answer

Akira Agata
Akira Agata on 16 Dec 2017
By using bwperim, regionprops and pdist2 functions, you can obtain the minimum distance and corresponding points on each object, like:
% Import your image and binarize
I = imread('aa.jpg');
BW = imbinarize(rgb2gray(I));
% Measure the minimum distance
BW2 = bwperim(BW,8);
stats = struct2table(regionprops(BW2,'PixelList'));
dist = pdist2(stats.PixelList{1},stats.PixelList{2});
[dmin,idx] = min(dist(:));
[r,c] = ind2sub(size(dist),idx);
pt1 = stats.PixelList{1}(r,:);
pt2 = stats.PixelList{2}(c,:);
% Show the result
imshow(BW)
hold on
plot([pt1(1) pt2(1)],[pt1(2) pt2(2)],'r-o','LineWidth',2)
disp(sprintf('Min. distance: %f [pixel]',dmin))
The minimum distance in pixel was measured to be:
Min. distance: 476.822818 [pixel]
  4 Comments
mridul ghosh
mridul ghosh on 6 May 2018
Edited: mridul ghosh on 6 May 2018
Sir, pls tell what modification is required in your code in case the distances between more than two objects are needed in an image..
Akira Agata
Akira Agata on 6 May 2018
If your image has N objects, the minimum distance and corresponding points between i th and j th objects can be calculated by modifying the code as follows (note: 1 <= i,j <= N and i ~= j).
dist = pdist2(stats.PixelList{i},stats.PixelList{j});
[dmin,idx] = min(dist(:));
[r,c] = ind2sub(size(dist),idx);
pt1 = stats.PixelList{i}(r,:);
pt2 = stats.PixelList{j}(c,:);

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