>> clear
>> I = imread('target.jpg');
figure, imshow(I);
>> th = graythresh(I);
BW = ~im2bw(I,th);
figure, imshow(BW);
>> bw_a = padarray(BW,[1 1],1,'pre');
BW = imfill(bw_a,'holes');
BW = BW(2:end,2:end);
figure, imshow(BW);
>> imgTwoAdjacent = bwareaopen(BW,5420); %figure, imshow(imgTwoAdjacent);
imgRemain1 = imsubtract(BW,imgTwoAdjacent);        %figure, imshow(imgRemain1);
imgMedium = bwareaopen(imgRemain1,2275);                 %figure, imshow(imgMedium);
imgSmall = imsubtract(logical(imgRemain1),imgMedium);   %figure, imshow(imgSmall);
>> [imgMedium,numMedium] = bwlabel(imgMedium);
figure, imshow(imgMedium);
title(['#medium: ' num2str(numMedium) '']);
>> [imgSmall,numSmall] = bwlabel(imgSmall);
figure, imshow(imgSmall);
title(['#small: ' num2str(numSmall) '']);
>> [imgTwoAdjacent,numTwoAdjacent] = bwlabel(imgTwoAdjacent);
figure, imshow(imgTwoAdjacent);
title(['#2 Cell: ' num2str(numTwoAdjacent) '']);