clc,clear,close all
%% 中轴线算法

a = imread('cl.jpg');
a  = im2bw( a );

m = zeros( size(a) );

figure
imshow(a)


for i = 1:size(m,1)
    for j = 1:size(m, 2)
        if a(i,j)
           sd = 0;
           tmp = 1;
           while all( tmp )
               sd = sd + 1;
               u = max(i - sd , 1);
               d = min(i + sd , size(m,1));
               l = max(j - sd , 1);
               r = min(j + sd , size(m,2));
               tmp = a( u:d, l:r );
               m(i,j) = sum(tmp(:));
           end
        end
    end
end
figure
imshow(m , [])


%% 
t  = false( size(a) );
for i = 2:size(m,1)-1
    for j = 2:size(m, 2)-1
        if m(i,j) >= 20
            tmp = m(i-1:i+1,j-1:j+1);
            tmp = tmp(:);
%             tmp([1 3 7 9]) = [];
            tmp = sort(tmp);
            if m(i,j) >= tmp(end-1);
    %                 && m(i,j)>=m(i-1,j-1) && m(i,j)>=m(i+1,j+1) && ...
    %                 m(i,j)>=m(i+1,j-1) && m(i,j)>=m(i-1,j+1)
                t(i,j) = true;
            end
        end
    end
end
figure
imshow( t )

原图：

处理后的图片：