Numbering bubbles and extract centers

I have a 2D image of bubbles (all connected to each other). I want to number each bubble seperately, compute its area and locate centre of each bubble along with its co-ordinatres. Can I do it with standard flood fill algorithm? attaching skeletonized image for reference.

Answer 1

[KSSV]

You can count the number of closed regions using bwlabeln.

I = imread('test2.png') ;
I = rgb2gray(I) ;
[L,num] = bwlabeln(I,6) ;  % num gives you closed region 
m = regionprops(L) ;   % measurements of regions, gives centers of the regions
imshow(I)
hold on
for i = 1:num
    c = m(i).Centroid ;
    plot(c(1),c(2),'*r') ;
end

num gives you the number of closed regions. You can view them using vislabels(L). Download the function vislabels from here .

[Mandar Badve]

Thank you KSSV. It works fine!

[KSSV]

Just curious...May I know what image is this? What is the application?

[Mandar Badve]

Is it possible to estimate velocity of the bubbles once I extract centres from the images? By analysing successive frames? Or is there any way to track shapes between successive frames to estimate velocities?

Answer 2

[Abel Babu]

Hi Mandar,

Here is a MATLAB example that describes how to find circles in a given image:

https://in.mathworks.com/help/images/examples/detect-and-measure-circular-objects-in-an-image.html

It uses the ' imfindcircles ' function that internally uses Hough Transform to compute both center and radii of a circle. Here is the documentation for the same:

https://in.mathworks.com/help/images/ref/imfindcircles.html

Abel