m = imread('cbnimg.jpg');
imshow(m)
im = mean(m,3);
im = (im-min(im(:))) / (max(im(:))-min(im(:)));
figure;
imshow(im,[]);
impixelinfo
figure;

bin = im2bw(im);
imshow(bin);
figure;
bin = edge(bin);
SE = strel('disk',2);
cir =~imdilate(bin,SE);
imshow(cir);