clear;
pollenmat = imread('Fig3.10(b).jpg');
u = double(pollenmat);
[nx ny] = size(u)
nshades = 256;
hist= zeros(nshades,1);
for i=1:nx
    for j=1:ny
        for k=0:nshades-1
            if u(i,j)==k
                hist(k+1)=hist(k+1)+1;
            end
        end
    end
end
plot(hist);