MATLAB: How to calculate diameter of object

centroiddiameterimage processingImage Processing Toolboxmaskregionsegmentation

I have the following code to find the centroids of the particles within this image <- Hyperlink:-

I would like to calculate the diameter of each of the particles so to generate the diameter distribution of the entire image.

X=Image;
template = fspecial('LoG',[51,51],3); % produces a laplacian of Gaussian curve as a template mask use to compare all the intensities in the image
y = conv2(double(X),-template,'same'); % convolves the image with the template to find all the points which correspond to the template mask
FoVY = y(500:700,730:940);
Peaks = imregionalmax(FoVY); % finds all the local maxima
imagesc(Peaks)
LPeaks = bwlabel(Peaks);
R = regionprops(LPeaks);
FoVY = X(500:700,730:940);
imagesc(FoVY);
hold on;
for i = 1:length(R)
    plot(R(i).Centroid(1),R(i).Centroid(2),'r.');
    centroid = cat(1, R.Centroid);
end
no_of_collagen=length(centroid);

Best Answer

You can call regionprops() and then ask for EquivDiameter. You might get batter, more comprehensive answers if you put as much effort into your question here on the Mathworks MATLAB Central as you did for some other forum.

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Do you mean like 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 = 22;
%--------------------------------------------------------------------------------------------------------

%    READ IN IMAGE
folder = pwd;
baseFileName = 'Q4_4.png';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
	% The file doesn't exist -- didn't find it there in that folder.
	% Check the entire search path (other folders) for the file by stripping off the folder.
	fullFileNameOnSearchPath = baseFileName; % No path this time.
	if ~exist(fullFileNameOnSearchPath, 'file')
		% Still didn't find it.  Alert user.
		errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
		uiwait(warndlg(errorMessage));
		return;
	end
end
grayImage = imread(fullFileName);
% Get the dimensions of the image.
% numberOfColorChannels should be = 1 for a gray scale image, and 3 for an RGB color image.
[rows, columns, numberOfColorChannels] = size(grayImage)
if numberOfColorChannels > 1
	% It's not really gray scale like we expected - it's color.
	% Use weighted sum of ALL channels to create a gray scale image.
	grayImage = rgb2gray(grayImage);
	% ALTERNATE METHOD: Convert it to gray scale by taking only the green channel,
	% which in a typical snapshot will be the least noisy channel.
	% grayImage = grayImage(:, :, 2); % Take green channel.
end
% Display the image.
subplot(2, 3, 1);
imshow(grayImage);
axis('on', 'image');
title('Original Grayscale Image', 'FontSize', fontSize, 'Interpreter', 'None');
impixelinfo;
hFig = gcf;
hFig.WindowState = 'maximized'; % May not work in earlier versions of MATLAB.
drawnow;
%--------------------------------------------------------------------------------------------------------
% Binarize the image.
binaryImage = ~imbinarize(grayImage);
% Get rid of particles less than 200 in area.
binaryImage = bwareaopen(binaryImage, 200);
% Eliminate partial blobs - those touching the edge of the image.
binaryImage = imclearborder(binaryImage);
subplot(2, 3, 2);
imshow(binaryImage, []);
axis('on', 'image');
title('Mask Image', 'FontSize', fontSize, 'Interpreter', 'None');
impixelinfo;
drawnow;
% Find blobs
props = regionprops(binaryImage, 'Centroid', 'Area');
xy = vertcat(props.Centroid)
allAreas = [props.Area];
subplot(2, 3, 3);
histogram(allAreas, 10);
grid on;
title('Histogram of Blob Areas', 'FontSize', fontSize, 'Interpreter', 'None');
xlabel('Area', 'FontSize', fontSize, 'Interpreter', 'None');
ylabel('Count', 'FontSize', fontSize, 'Interpreter', 'None');
% Get blobs smaller than 2500
[labeledImage, numBlobs] = bwlabel(binaryImage);
smallIndexes = find(allAreas < 2500);
largeIndexes = find(allAreas >= 2500);
% Extract the small blobs with ismember()
smallBlobs = ismember(labeledImage, smallIndexes);
subplot(2, 3, 4);
imshow(smallBlobs);
title('Small Blobs', 'FontSize', fontSize, 'Interpreter', 'None');
% Extract the large blobs with ismember()
largeBlobs = ismember(labeledImage, largeIndexes);
subplot(2, 3, 5);
imshow(largeBlobs);
title('Large Blobs', 'FontSize', fontSize, 'Interpreter', 'None');

MATLAB: 1. How do i get Centroid and its corresponding Equivdiameter when regionprops is used

stats = regionprops(TheImage, 'Centroid', 'EquivDiameter');
stats(1).Centroid
stats(1).EquivDiameter

Best Answer

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MATLAB: Separate two type of object in the image

MATLAB: 1. How do i get Centroid and its corresponding Equivdiameter when regionprops is used

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