img_A=imread('..\immagini\im1.tif','tif'); 

S=double(img_A(:,:,1))+double(img_A(:,:,2))+double(img_A(:,:,3));
soglia=10; L3=double(max(img_A(:)))*3;
img_t=double(S<soglia | S>(L-soglia));

imshow(img_t);

img_B=zeros(10,10); img_B(1:5,1:5)=1.0; img_B(6:10,6:10)=1.0;
imshow(img_B);

c = normxcorr2(img_B,img_t);
figure; surf(c), shading flat
figure; imshow(c/max(c(:)))

figure; imshow((c/max(c(:))>0.75));