A=imread('cell.tif');
subplot(3,3,[1,4,7]);
imshow(A);
pixval 
text(191,170,'Image courtesy of Alan Partin',...
   'FontSize',7,'HorizontalAlignment','right');
text(191,180,'Johns Hopkins University',...
    'FontSize',7,'HorizontalAlignment','right');

subplot(3,3,2);
B=edge(A,'sobel');
imshow(B);
title('binary gradient mask');

SE = strel('line',2,8);
C=imdilate(A,SE);
subplot(3,3,3);
imshow(A),title('Original');
subplot(3,3,5);
imshow(C),title('dilated gradient mask');

D=imfill(C);
subplot(3,3,6);
imshow(D),title('imfill');
E=imclearborder(D);
subplot(3,3,8);
imshow(E),title('imclearborder');
F=imerode(E,SE);
subplot(3,3,9);
imshow(F),title('imerode');