edu_imgpreprocess(I, selected_col,selected_ln)

function img = edu_imgpreprocess(I, selected_col,selected_ln)

Igray = rgb2gray(I);

Ibw = im2bw(Igray,graythresh(Igray));

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];
[y,x]=size(Ibox);
x=x/4;
Ibox = reshape(Ibox,[4 x]);

Ic = [Iprops.Centroid];
[z,w]=size(Ic);%
w=w/2;%
Ic = reshape(Ic,[2 w]);
Ic = Ic';
Ic(:,3) = (mean(Ic.^2,2)).^(1/2);
Ic(:,4) = 1:w;

% Extra lines compare to example2 to extract all the components into an
% cell array
Ic2 = sortrows(Ic,2);

for cnt = 1:selected_ln
   Ic2((cnt-1)*selected_col+1:cnt*selected_col,:) = sortrows(Ic2((cnt-1)*selected_col+1:cnt*selected_col,:),4);
end

Ic3 = Ic2(:,1:2);
ind = Ic2(:,4);

for cnt = 1:selected_ln*selected_col
    img{cnt} = imcrop(Ibw,Ibox(:,ind(cnt)));
end