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

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.

Answer 1

[Akira Agata]

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]

[Naseeb Gill]

Sir while I run above program it shows error

Undefined function 'imbinarize' for input arguments of type 'uint8'

because I have 2014b version while imbinarize was added from 2016a version. Is there any alternative for the same?

[Naseeb Gill]

Thanks @Akira Agata. I used

threshold = graythresh(I);
BW=im2bw(I,threshold);

instead of imbinarize and it works fine.

[mridul ghosh]

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]

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,:);