Find center of pixels in an image?

Hi, I have a picture like "Cattura"

I want to find the center of those little areas that we can see.

How can I do?

Answer 1

[Image Analyst]

Try this:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 18;
fprintf('Beginning to run %s.m ...\n', mfilename);
echo off;

s = load('FileDaAllegare.mat')
grayImage = s.E;
subplot(2, 2, 1);
imshow(imadjust(grayImage), []);
title('Contrast-stretched gray scale image', 'FontSize', fontSize);

subplot(2, 2, 2);
imhist(grayImage);
grid on;
title('Histogram of gray scale image', 'FontSize', fontSize);

% Binarize the image.
mask = grayImage > 0.5;
% Count the initial number of blobs.
[~, numBlobs] = bwlabel(mask);
fprintf('Found %d blobs initially.\n', numBlobs);
% Merge close blobs together with a morphologcal closing.
windowRadius = 7;
se = strel('disk', windowRadius, 0);
mask = imclose(mask, se);
subplot(2, 2, 3);
imshow(mask, []);
title('Binary image', 'FontSize', fontSize);

props = regionprops(mask, 'Area', 'Centroid');
numBlobs = length(props);
% Get all the areas.
allAreas = [props.Area];
% Get all the centroids.  Column 1 is x, column 2 is y.
centroidsXY = vertcat(props.Centroid);
fprintf('Found %d blobs after filtering.\n', numBlobs);

% Show histogram of areas.
subplot(2, 2, 4);
histogram(allAreas);
grid on;
caption = sprintf('Histogram of %d Blob Areas', numBlobs);
title(caption, 'FontSize', fontSize);

g = gcf;
g.WindowState = 'maximized';

Answer 2

[Image Analyst]

I go over this in my Image Segmentation Tutorial

Image Analyst's File Exchange

Attach your original gray scale image (not a pseudocolored screenshot) if you need more help.

[Alberto Paniate]

I have tried to use you programme, but I don't have a great results, I really dont know how to detect them because they have different size (and they arent perfect circle) and different intensity

[Image Analyst]

Did you not see the last line in my answer?

[Alberto Paniate]

Yes, sorry. Tell me if this is ok:

[Image Analyst]

No - that's another screenshot. Give me the image as you originally read it from disk and before you called imagesc and exported a screenshot of it. I want a grayscale image BEFORE it has been pseudocolored by imagesc() or colormap(). The image you gave makes it harder to determine the intensities of the pixels. It's still possible but we'd have to do color segmentation instead of simple thresholding, then we'd have to have code to throw away the white background and black tick marks and labels. It would be so much easier if you could just give me the original image.

[Alberto Paniate]

That picture is a matrix that I calculate on a program. Here there is the matrix.

https://drive.google.com/file/d/1qHxXnIYlxP2ZdvJzjCm8jZJefzh8XHvv/view?usp=sharing

[Image Analyst]

Can you make easy on us and please attach it here with the paper clip icon? We'd like the solution to be completely self contained here within the Answers forum, not spread across different web sites. I'll check back later.

[Alberto Paniate]

I cant the dimension is 29 MB even zipping it