im = imread('grains.jpg');
im2 = rgb2gray(im);

level = graythresh(im2);
BW = im2bw(im2,level);
imshow(BW)

se = strel('disk',7);

%% morphological operations

a_erode = imerode(BW,se);
figure , imshow(a_erode) , title('eroded image') 

a_dilate = imdilate(BW, se);
figure , imshow(a_dilate) , title('dilated image')


a_open = imopen(BW, se);
figure , imshow(a_open) , title('opened image')

a_closed = imclose(BW,se);
figure , imshow(a_closed) , title('closed image')


I = imread('coins.png');
imshow(I)
level = graythresh(I);
BW = im2bw(I, level);
imshow(BW)
BW2 = imfill(BW, 'holes');
imshow(BW2)