Try this. Adapt as needed. Let me know if you can or not.
% Program to find the circle regions in a demo image.
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
imtool close all; % Close all imtool figures if you have the Image Processing Toolbox.
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;
%===============================================================================
% Check that user has the Image Processing Toolbox installed.
hasIPT = license('test', 'image_toolbox');
if ~hasIPT
% User does not have the toolbox installed.
message = sprintf('Sorry, but you do not seem to have the Image Processing Toolbox.\nDo you want to try to continue anyway?');
reply = questdlg(message, 'Toolbox missing', 'Yes', 'No', 'Yes');
if strcmpi(reply, 'No')
% User said No, so exit.
return;
end
end
%===============================================================================
% Read in the gray scale demo image.
folder = pwd;
baseFileName = 'iso.png';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
% File doesn't exist -- didn't find it there. Check the search path for it.
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.
% numberOfColorBands should be = 1.
[rows, columns, numberOfColorBands] = size(grayImage);
if numberOfColorBands > 1
% It's not really gray scale like we expected - it's color.
% Convert it to gray scale by taking only the green channel.
grayImage = grayImage(:, :, 2); % Take green channel.
end
% Display the original gray scale image.
subplot(2, 3, 1);
imshow(grayImage, []);
axis on;
title('Original Grayscale Image', 'FontSize', fontSize);
drawnow;
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
%===============================================================================
% Let's compute and display the histogram.
[pixelCount, grayLevels] = imhist(grayImage);
% The first and last bin of pixelCount are so huge that it suppresses the height
% of the rest of the histogram when plotted. Zero out these bins so we can see the other bins.
pixelCount(1) = 0;
pixelCount(end) = 0;
subplot(2, 3, 2);
bar(grayLevels, pixelCount, 'BarWidth', 1, 'FaceColor', 'b');
grid on;
title('Histogram of Original Image', 'FontSize', fontSize);
xlim([0 grayLevels(end)]); % Scale x axis manually.
%===============================================================================
% Threshold (binarize) the image.
thresholdValue = 25;
% Draw a red line on the histogram at this value.
line([thresholdValue, thresholdValue], ylim, 'LineWidth', 2, 'Color', 'r');
% Label the regions for the two body zones.
text(28, 1500, 'Threshold = 25', 'Color', 'r', 'FontSize', 20, 'FontWeight', 'bold');
binaryImage = grayImage > thresholdValue; % Do the thresholding.
% Display the binary image.
subplot(2, 3, 3);
imshow(binaryImage, []);
axis on;
title('Binary Image', 'FontSize', fontSize);
drawnow;
% Get rid of stuff touching the border
binaryImage = imclearborder(binaryImage);
% Extract only the two largest blobs.
binaryImage = bwareafilt(binaryImage, 1);
% Fill holes in the blob to make it solid.
binaryImage = imfill(binaryImage, 'holes');
% Display the binary image.
subplot(2, 3, 4);
imshow(binaryImage, []);
axis on;
title('Circle-Only Binary Image', 'FontSize', fontSize);
drawnow;
% Mask image with circle-only mask.
% This will produce a gray scale image in the circle and black everywhere else.
maskedImage = grayImage; % Initialize
maskedImage(~binaryImage) = 0;
% Display the masked gray scale image of only the circle.
subplot(2, 3, 5);
imshow(maskedImage, []);
axis on;
title('Masked Circle-Only Image', 'FontSize', fontSize);
% Label the image
labeledImage = bwlabel(binaryImage);
props = regionprops(labeledImage, 'Centroid', 'Area');
% Plot a big red cross over the centroid.
hold on;
plot(props.Centroid(1), props.Centroid(2), 'r+', 'MarkerSize', 50);
message = sprintf('The Area = %f.\nThe Centroid is at (x,y) = (%f, %f)', ...
props.Area, props.Centroid);
uiwait(helpdlg(message));
