data = dir('images/*.bmp');
for i = 1:length(data)
    filename = data(i).name;
    a = imread(strcat('images/', filename));
    [r,c] = size(a);
    for i=1:r
        for j = 1:c
            if(a(i,j) > 128 )
                a(i,j) = 255;
            end
            if(a(i,j) <= 128)
                 a(i,j) = 0;
            end
        end
    end
    imwrite(a,strcat('images2/', filename));
end