## Copyright (C) 2000 Dave Cogdell <cogdelld@asme.org>
## Copyright (C) 2000 Paul Kienzle <pkienzle@users.sf.net>
## Copyright (C) 2012 CarnĂŤ Draug <carandraug+dev@gmail.com>
## Copyright (C) 2014 Benjamin Eltzner <b.eltzner@gmx.de>
##
## This program is free software; you can redistribute it and/or modify it under
## the terms of the GNU General Public License as published by the Free Software
## Foundation; either version 3 of the License, or (at your option) any later
## version.
##
## This program is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
## details.
##
## You should have received a copy of the GNU General Public License along with
## this program; if not, see <http://www.gnu.org/licenses/>. 

function c = xcorr2coeff_alt (a, b)

  %%%%% as lines 69-71 %%%%%
  [ma,na] = size(a);
  [mb,nb] = size(b);
  c = conv2 (a, conj (b (mb:-1:1, nb:-1:1)));
  %%%%%

  %%%%% insert this instead of lines 94-98 %%%%%
  a = double (a);
  b = double (b);
  b = b.-mean2(b);
  c = conv2 (a, conj (b (mb:-1:1, nb:-1:1)));
  means_a = conv2 (a, (ones (size (b))) ./ (mb*nb));
  squares_a = conv2 (a.^2, ones (size (b)));
  a = squares_a .- (mb*nb) .* means_a.^2;
  b = sumsq (b(:));
  c(:,:) = c(:,:) ./ sqrt (a(:,:) * b);
  c(isnan(c)) = 0;
  %%%%%