Hi,
To divide a matrix into submatrices of equal size, you can use the "reshape" function instead of "mat2cell". "reshape" can only divide a matrix into submatrices of equal size, so you'll need to pad your image with zeros to ensure it can be evenly divided into 9x9 submatrices.
To create optimal subgroups that cover the entire head, you can use a sliding window approach. The idea is to slide a 9x9 window over the head and record the positions where the window covers non-zero pixels. Then, you can group these positions into subgroups that cover the entire head.
Example:
% Load the image
image = imread('head_ct.png');
% Extract the head region
head_region = image(size(image, 1)*0.15:end, :, :);
% Initialize a binary mask that indicates which pixels are non-zero in the head region
mask = head_region > 0;
% Slide a 9x9 window over the head region and record the positions where the window covers non-zero pixels
positions = [];
for i = 1:size(head_region, 1)-8
for j = 1:size(head_region, 2)-8
window = mask(i:i+8, j:j+8);
if sum(window(:)) == 81
positions = [positions; i, j];
end
end
end
% Cluster the positions into subgroups that cover the entire head
[idx, C] = kmeans(positions, ceil(size(positions, 1)/9));
subgroups = cell(1, max(idx));
for i = 1:max(idx)
subgroups{i} = positions(idx == i, :);
end
% Display the subgroups
figure;
imshow(head_region);
hold on;
colors = hsv(max(idx));
for i = 1:max(idx)
scatter(subgroups{i}(:, 2), subgroups{i}(:, 1), 5, colors(i, :), 'filled');
end
