pocs.m

function y = pocs(s,delta_est,factor)
% POCS - reconstruct high resolution image using Projection On Convex Sets
%    y = pocs(s,delta_est,factor)
%    reconstruct an image with FACTOR times more pixels in both dimensions
%    using Papoulis Gerchberg algorithm and using the shift and rotation
%    information from DELTA_EST and PHI_EST
%    in:
%    s: images in cell array (s{1}, s{2},...)
%    delta_est(i,Dy:Dx) estimated shifts in y and x
%    factor: gives size of reconstructed image

%% -----------------------------------------------------------------------
% SUPERRESOLUTION - Graphical User Interface for Super-Resolution Imaging
% Copyright (C) 2005-2007 Laboratory of Audiovisual Communications (LCAV),
% Ecole Polytechnique Federale de Lausanne (EPFL),
% CH-1015 Lausanne, Switzerland
%
% 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 2 of the License, or (at your
% option) any later version. This software 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
% (enclosed in the file GPL).
%
% Latest modifications: August 20, 2006, by Karim Krichane

max_iter = 50;

temp = upsample(upsample(s{1}, factor)', factor)';
y = zeros(size(temp));
coord = find(temp);
y(coord) = temp(coord);


for i = 2:length(s)
    temp = upsample(upsample(s{i}, factor)', factor)';
    temp = imshift(temp, round(delta_est(i, 2)*factor), round(delta_est(i, 1)*factor));
    coord = find(temp);
    y(coord) = temp(coord);
end

y_prev=y;

E=[];
iter=1;

blur =[.25 0 1 0 .25;...
        0  1 2 1  0;...
        1  2 4 2  1;...
        0  1 2 1  0;...
       .25 0 1 0 .25];

blur = blur / sum(blur(:));

while iter < max_iter
   y = imfilter(y, blur);
   for i = length(s):-1:1
        temp = upsample(upsample(s{i}, factor)', factor)';
        temp = imshift(temp, round(delta_est(i, 2)*factor), round(delta_est(i, 1)*factor));
        coord = find(temp);
        y(coord) = temp(coord);
   end

   delta= norm(y-y_prev)/norm(y);
   E=[E; iter delta];
   iter = iter+1;
   if iter>3
     if abs(E(iter-3,2)-delta) <1e-4
        break
     end
   end
   y_prev=y;
%    if mod(iter,10)==2
%        disp(['iteration ' int2str(E(iter-1,1)) ', error ' num2str(E(iter-1,2))])
%    end
end