How to get centroid specific part of an image
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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.
Accepted Answer
Christiaan
on 10 Mar 2015
Edited: Christiaan
on 10 Mar 2015
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

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More Answers (2)
Image Analyst
on 10 Mar 2015
My Image Segmentation Tutorial shows you how to get centroids.
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