Something like this seems to work:
img = imread('testimage.jpg');
bw = imbinarize(im2gray(img),'adaptive','Sensitivity',0.45);
info = regionprops(bw, 'all');
imshow(img);
hold on;
minSize = 50; % ignore small/noise regions (adjust as necessary)
angles = [];
for k = 1:length(info)
% get region properties
w = info(k).MajorAxisLength;
h = info(k).MinorAxisLength;
x = info(k).Centroid(1) - w/2;
y = info(k).Centroid(2) - h/2;
theta = info(k).Orientation;
if h < minSize % skip the small/noise regions
continue;
end
angles = [angles theta];
ps = polyshape([x, x, x+w, x+w], [y, y+h, y+h, y]);
ps2 = rotate(ps, -theta, [x+w/2 y+h/2]);
plot(ps2, 'EdgeColor','r', 'FaceColor','none', 'LineWidth',2);
end
angles
