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diff --git a/SD-VBS/benchmarks/sift/src/matlab/diffss.m b/SD-VBS/benchmarks/sift/src/matlab/diffss.m
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+function dss = diffss(ss)
+% DIFFSS  Difference of scale space
+%   DSS=DIFFSS(SS) returns a scale space DSS obtained by subtracting
+%   consecutive levels of the scale space SS.
+%
+%   In SIFT, this function is used to compute the difference of
+%   Gaussian scale space from the Gaussian scale space of an image.
+%
+%   See also GAUSSIANSS(), PDF:SIFT.USER.SS.
+
+% AUTORIGHTS
+% Copyright (c) 2006 The Regents of the University of California.
+% All Rights Reserved.
+% 
+% Created by Andrea Vedaldi
+% UCLA Vision Lab - Department of Computer Science
+% 
+% Permission to use, copy, modify, and distribute this software and its
+% documentation for educational, research and non-profit purposes,
+% without fee, and without a written agreement is hereby granted,
+% provided that the above copyright notice, this paragraph and the
+% following three paragraphs appear in all copies.
+% 
+% This software program and documentation are copyrighted by The Regents
+% of the University of California. The software program and
+% documentation are supplied "as is", without any accompanying services
+% from The Regents. The Regents does not warrant that the operation of
+% the program will be uninterrupted or error-free. The end-user
+% understands that the program was developed for research purposes and
+% is advised not to rely exclusively on the program for any reason.
+% 
+% This software embodies a method for which the following patent has
+% been issued: "Method and apparatus for identifying scale invariant
+% features in an image and use of same for locating an object in an
+% image," David G. Lowe, US Patent 6,711,293 (March 23,
+% 2004). Provisional application filed March 8, 1999. Asignee: The
+% University of British Columbia.
+% 
+% IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
+% FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES,
+% INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND
+% ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN
+% ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. THE UNIVERSITY OF
+% CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
+% LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+% A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS"
+% BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE
+% MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+
+dss.smin = ss.smin ;
+dss.smax = ss.smax-1 ;
+dss.omin = ss.omin ;
+dss.O = ss.O ;
+dss.S = ss.S ;
+dss.sigma0 = ss.sigma0 ;
+
+for o=1:dss.O
+  % Can be done at once, but it turns out to be faster
+  % this way
+  [M,N,S] = size(ss.octave{o}) ;
+  dss.octave{o} = zeros(M,N,S-1) ;
+  for s=1:S-1
+    dss.octave{o}(:,:,s) = ...
+        ss.octave{o}(:,:,s+1) - ss.octave{o}(:,:,s) ;
+  end
+end
+
+%    for i=1:32
+%        for j=1:32
+%            fprintf(1, '%f\n', dss.octave{1}(i,j,1));
+%        end
+%    end