function mypoint(f,percent)
figure(1)
imshow(f);
ff=double(f);
w = [-1 -1 -1; -1 8 -1; -1 -1 -1];
g=abs(imfilter(ff, w));
%g=abs(imfilter(double(f), w));
T=max(g(:));
g = g>=percent*T;
figure(2); imshow(g)
m=3; n=3;
h=imsubtract(ordfilt2(ff,m*n,ones(m,n)), ordfilt2(ff,1,ones(m.n)));
 %                             ordfilt2(ff,m*n-1,ones(,m.n)));
 h=h>=percent*T;
figure(3); imshow(h)