%IM_MEAN Fixed mapping computating the centers of gravity of images
%
% B = IM_MEAN(A)
% B = A*IM_MEAN
%
% INPUT
% A Dataset with object images dataset (possibly multi-band)
%
% OUTPUT
% B Dataset with centers-of-gravity replacing images
% (possibly multi-band). The first component is always measured
% in the horizontal direction (X).
%
% DESCRIPTION
% Computes the centers of gravity of all images stored in A.
% This center is computed, relative to the top-left corner of the image.
%
% SEE ALSO (<a href="http://37steps.com/prtools">PRTools Guide</a>)
% DATASETS, DATAFILES
% Copyright: R.P.W. Duin, r.p.w.duin@37steps.com
% Faculty EWI, Delft University of Technology
% P.O. Box 5031, 2600 GA Delft, The Netherlands
function b = im_mean(a)
if nargin < 1 | isempty(a)
b = prmapping(mfilename,'fixed');
b = setname(b,'Image centers');
elseif isa(a,'prdataset') % allows datafiles too
isobjim(a);
b = filtim(a,mfilename);
elseif isa(a,'double') % here we have a single image
if isa(a,'dip_image'), a = double(a); end
[m,n] = size(a);
g = sum(sum(a));
JX = repmat([1:n],m,1);
JY = repmat([1:m]',1,n);
mx = sum(sum(a.*JX))/g;
my = sum(sum(a.*JY))/g;
b = [mx/n my/m];
end
return