How can i find distance between surf feature point on a signature image in oder to varify real signature or not.

E= imread('1.png');
F=rgb2gray(E);
G= imsharpen(F,'Radius',2,'Amount',1);
H=im2bw(G);
%   points= detectSURFFeatures(l);
figure;
imshow(H); hold on; 
 title('Image Of H');
%   plot(points);

 A = imread('4.png');
 B=rgb2gray(A);
 C= imsharpen(B,'Radius',2,'Amount',2);
 D=im2bw(C);
 figure;
  imshow(D); hold on;
title('Image Of D');

hPoints = detectSURFFeatures(H); dPoints = detectSURFFeatures(D);

figure; imshow(H); title('200 Strongest Feature Points from H Image'); hold on; plot(selectStrongest(hPoints, 200));

figure; imshow(D); title('200 Strongest Feature Points from D Image'); hold on; plot(selectStrongest(dPoints, 200));

this are the code for feature extraction