This is a MATLAB function that pixelates a given image with parameter w. uses a 2w+1 mask size for blurring.

pixelate.m

function W = pixelate(I, w)
    [n, m, ~] = size(I);
    W = I;
    
    for row = w + 1 : 2 * w + 1 : n + w
        for column = w + 1 : 2 * w + 1 : m + w
            row_upper = upper(row + w, n, n);
            column_upper = upper(column + w, m, m);
            sub_image = I(row - w : row_upper, column - w : column_upper, :);
            average = mean(mean(sub_image));
            W(row - w : row_upper, column - w : column_upper, :) = average .* ...
                ones(row_upper - row + w + 1, column_upper - column + w + 1, 3);
        end
    end
end

function value = upper(value, threshold, default)
    if value > threshold
        value = default;
    end
end

hi, how did you plot the pixellated image?

We can display any mage in matlab using the imshow() method. after calling this function simply pass in the returned image in imshow(R) where R is the result.

imshow(R);