MATLAB: How to get centroid specific part of an image

centroiddigital image processingImage Processing Toolbox

I am intended to compute centroid of a part of image. I am getting centroid of all parts of the image which makes me confused of selecting the right one. my code is:
I = imread('Murine_Tibia_Crosssection.png')
Ibw = im2bw(I);
Ibw = imfill(Ibw,'holes');
Ilabel = bwlabel(Ibw);
stat = regionprops(Ilabel,'centroid');
imshow(I); hold on;
for x = 1: numel(stat)
  plot(stat(x).Centroid(1),stat(x).Centroid(2),'ro');
end
please help me to get the right one.

Best Answer

Dear Ajay,
If an image shows multiple centroids, there are some tricks to still determine the centroid. First you can filter the image using the function medfilt2. Then you can make the image black and white with the function im2bw. Finally you can fill holes when the size of the hole is smaller than a specific size with the function bwareaopen.
See the code below for an example:
clc;clear all;close all;
I = imread('Murine_Tibia_Crosssection.png');
figure(1)
imshow(I)
stat = regionprops(I,'centroid'); 
I_filtered = medfilt2(I, [12 12]);
figure(2)
imshow(I_filtered)
level = graythresh(I_filtered)
BlackWhite = im2bw(I_filtered, level);
figure(3)
imshow(BlackWhite);
original = BlackWhite;
filled = imfill(original, 'holes');
holes = filled & ~original;
bigholes = bwareaopen(holes, 500);
smallholes = holes & ~bigholes;
new = original | smallholes;
figure(4)
imshow(new);
stat = regionprops(new,'centroid'); 
hold on; for x = 1: numel(stat) 
    plot(stat(x).Centroid(1),stat(x).Centroid(2),'ro','linewidth',5); 
end
hold off
Good luck! Christiaan
Related Question