find symmetry in image in matlab

main.m
% read in the image
original_image = imread('image.jpg');

% convert the image to grayscale
grayscale_image = rgb2gray(original_image);

% apply edge detection to extract the edges
edge_image = edge(grayscale_image, 'Canny');

% find the Hough transform of the image
hough_transform = hough(edge_image);

% find the peaks in the Hough transform
peaks = houghpeaks(hough_transform);

% extract the lines from the Hough transform
lines = houghlines(edge_image, hough_transform, peaks);

% create a mirror image of the original image
mirrored_image = flip(original_image, 2);

% measure the symmetry of the image by finding the difference between the
% original image and the mirrored image along the detected lines
symmetry = zeros(length(lines), 1);
for i = 1:length(lines)
    x1 = lines(i).point1(1);
    y1 = lines(i).point1(2);
    x2 = lines(i).point2(1);
    y2 = lines(i).point2(2);
    
    % create a mask of the line
    mask = poly2mask([x1 x2 x2 x1], [y1 y1 y2 y2], size(original_image,1), size(original_image,2));
    
    % extract the pixels along the line from the original and mirrored image
    line_pixels_original = double(grayscale_image(mask));
    line_pixels_mirrored = double(grayscale_image(mask & flip(mask, 2)));
    
    % calculate the difference between the original and mirrored image
    symmetry(i) = sum(abs(line_pixels_original - line_pixels_mirrored));
end

% plot the detected lines on the original image
figure
imshow(original_image);
hold on;
for i = 1:length(lines)
   xy = [lines(i).point1; lines(i).point2];
   plot(xy(:,1),xy(:,2),'LineWidth',2,'Color','green');
end
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