find angle frome centroid area output not true

im = imcrop(BW,[min(columns),min(rows),width,height]);
[r,c] = find(im,1,'first');
theta = atan2(cen(1,1)-c,cen(1,2)-r);
theta = radtodeg(theta);
hold on
plot(cen(:,1),cen(:,2),'b*')
line ([cen(:,1) r],[cen(:,2) c]);

%find center
[y, x] = ndgrid(1:size(BW, 1), 1:size(BW, 2));
cen = mean([x(logical(BW)), y(logical(BW))]);

I use this code find angle use find white area first but some picture has output of angle is 30 not true help me

[KSSV]

If the angle result, is not true; check whether your cen exactly is center or not.