rotateImage.m

inputfile = "data/1.bmp";

imsrc = imread(inputfile);   % Load an RGB image
imresized = imresize(imsrc, [28 NaN]);  % Resize image
imbw = im2bw(imresized, "moments"); % Convert to binary

% Get the positions of the black pixels
x = []; y = [];
for r = 1:28
    for c = 1:size(imbw, 2)
        if imbw(r, c) == 0
            x = [x; r];
            y = [y; 28-c];
        end
    end
end

% plot(x, y, "rx", "MarkerSize", 8); % Plot the data

m = length(x);  % Count how many data points we have
X = [ones(m, 1) x]; % Add a column of all ones (intercept term) to x

theta = (pinv(X' * X)) * X' * y; % Calculate theta

% Plot the fitted equation we got from the regression
% hold on;
% plot(X(:, 2), X * theta, '-');
% hold off;

imfinal = imrotate (imsrc, -theta(2), "bicubic", "loose", 0);

[path, name, ext] = fileparts(inputfile);
outpath = fullfile(path, "out");
if ~exist(outpath, "dir")
  mkdir(outpath);
end
outfile = fullfile(outpath, strcat(name, ext));
imwrite(imfinal, outfile)

fprintf("Output saved as: %s\n", outfile)