照这个用
function img = edu_imgpreprocess(I) %图像预处理
Igray = rgb2gray(I); %转化成灰色图像
Ibw = im2bw(Igray,graythresh(Igray));%转化成二值 graythresh返回图像的阈值和阈值的有效性
Iedge = edge(uint8(Ibw));
se = strel('square',3);
Iedge2 = imdilate(Iedge, se);
Ifill= imfill(Iedge2,'holes');
[Ilabel num] = bwlabel(Ifill);
Iprops = regionprops(Ilabel);
Ibox = [Iprops.BoundingBox];
Ibox = reshape(Ibox,[4 50]);
Ic = [Iprops.Centroid];
Ic = reshape(Ic,[2 50]);
Ic = Ic';
Ic(:,3) = (mean(Ic.^2,2)).^(1/2);
Ic(:,4) = 1:50;
% Extra lines compare to example2 to extract all the components into an
% cell array
Ic2 = sortrows(Ic,2);
for cnt = 1:5
Ic2((cnt-1)*10+1:cnt*10,:) = sortrows(Ic2((cnt-1)*10+1:cnt*10,:),4);
end
Ic3 = Ic2(:,1:2);
ind = Ic2(:,4);
for cnt = 1:50
img{cnt} = imcrop(Ibw,Ibox(:,ind(cnt)));
end