function bin = exc4( img_path, out_path, varargin )

im = imread(img_path);
gray = rgb2gray(im);

if length(varargin) > 1
    error 'Túl sok paraméter!';
elseif length(varargin) < 1
    threshold = mean(gray(:));
else
    threshold = varargin{1};
end

logic_im = gray > threshold;
gray(logic_im == 0) = 0;
gray(logic_im == 1) = 255;

if exist(out_path, 'dir') == 7
    [path, name, ext] = fileparts(img_path);
    imwrite(gray,strcat(out_path, name, '_mixed', ext));
end

bin = gray;

end