%=======================================================================
% Copyright 2008-2016, LEGI UMR 5519 / CNRS UGA G-INP, Grenoble, France
%   http://www.legi.grenoble-inp.fr
%   Joel.Sommeria - Joel.Sommeria (A) legi.cnrs.fr
%
%     This file is part of the toolbox UVMAT.
%
%     UVMAT 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 2 of the license,
%     or (at your option) any later version.
%
%     UVMAT 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 (see LICENSE.txt) for more details.
%=======================================================================

function DataOut=im_levels(DataIn)
%% set GUI config: no action defined
DataOut=[];  %default  output field
if strcmp(DataIn,'*')
    return
end
%-----------------------------------------------
%parameters
np=30
%--------------------------------------------------------- 
DataOut=DataIn;%default

B=double(DataIn.A(:,:,1));
windowsize=round(min(size(B,1),size(B,2))/20);
windowsize=floor(windowsize/2)*2+1;
ix=[1/2-windowsize/2:-1/2+windowsize/2];%
%del=np/3;
%fct=exp(-(ix/del).^2);
fct2=cos(ix/((np-1)/2)*pi/2);
%Mfiltre=(ones(5,5)/5^2);
%Mfiltre=fct2';
Mfiltre=fct2'*fct2;
Mfiltre=Mfiltre/(sum(sum(Mfiltre)));

C=filter2(Mfiltre,B);
C(:,1:windowsize)=C(:,windowsize)*ones(1,windowsize);
C(:,end-windowsize+1:end)=C(:,end-windowsize+1)*ones(1,windowsize);
C(1:windowsize,:)=ones(windowsize,1)*C(windowsize,:);
C(end-windowsize+1:end,:)=ones(windowsize,1)*C(end-windowsize,:);
C=tanh(B./(2*C));
[n,c]=hist(reshape(C,1,[]),100);
% figure;plot(c,n);

[m,i]=max(n);
c_max=c(i);
[dummy,index]=sort(abs(c-c(i)));
n=n(index);
c=c(index);
i_select = find(cumsum(n)<0.95*sum(n));
if isempty(i_select)
    i_select = 1:length(c);
end
c_select=c(i_select);
n_select=n(i_select);
cmin=min(c_select);
cmax=max(c_select);
C=(C-cmin)/(cmax-cmin)*256;
DataOut.AA=uint8(C);



DataOut.A=uint8(C);
