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2026-09-17 19:39:08 +09:00 · 2026-08-07 15:56:42 +09:00
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+% IMSHIFT_FFT will apply shift with subpixel accuracy that can be different for  each frame. 
+%
+% img = imshift_fft(img, x,y, apply_fft = true, weights = [])
+%
+%  Inputs:
+%       **img - input image stack, can be complex valued  
+%       **x, y - shifts in number of pixels 
+%       **apply_fft , if false, then images will be assumed to be in fourier space 
+%       **weights - 0<W<=1 apply importance weighting to avoid noise in low reliability regions 
+%  returns: 
+%       ++img - shifted image stack 
+
+%*-----------------------------------------------------------------------*
+%|                                                                       |
+%|  Except where otherwise noted, this work is licensed under a          |
+%|  Creative Commons Attribution-NonCommercial-ShareAlike 4.0            |
+%|  International (CC BY-NC-SA 4.0) license.                             |
+%|                                                                       |
+%|  Copyright (c) 2017 by Paul Scherrer Institute (http://www.psi.ch)    |
+%|                                                                       |
+%|       Author: CXS group, PSI                                          |
+%*-----------------------------------------------------------------------*
+% You may use this code with the following provisions:
+%
+% If the code is fully or partially redistributed, or rewritten in another
+%   computing language this notice should be included in the redistribution.
+%
+% If this code, or subfunctions or parts of it, is used for research in a 
+%   publication or if it is fully or partially rewritten for another 
+%   computing language the authors and institution should be acknowledged 
+%   in written form in the publication: “Data processing was carried out 
+%   using the “cSAXS matlab package” developed by the CXS group,
+%   Paul Scherrer Institut, Switzerland.” 
+%   Variations on the latter text can be incorporated upon discussion with 
+%   the CXS group if needed to more specifically reflect the use of the package 
+%   for the published work.
+%
+% A publication that focuses on describing features, or parameters, that
+%    are already existing in the code should be first discussed with the
+%    authors.
+%   
+% This code and subroutines are part of a continuous development, they 
+%    are provided “as they are” without guarantees or liability on part
+%    of PSI or the authors. It is the user responsibility to ensure its 
+%    proper use and the correctness of the results.
+
+
+
+    
+function img = imshift_fft(img, x,y, apply_fft, weights)
+    
+    
+    if nargin  < 3
+        y = x(:,2);  % x can be either Nx1  or Nx2 vector 
+        x = x(:,1);
+    end
+    if nargin < 4
+        apply_fft = true; % if false, assume that img is already fft transformed 
+    end
+    if nargin < 5
+        weights = [];  % weights prevents amplitifaction of noise in low reliability regions 
+    end
+    if ~isempty(weights) && ~isscalar(weights)
+        eps_ = 1e2*eps(ones(1,'like',img)); 
+        weights = max(eps_, weights);  % avoid dividing by zero 
+    end
+    
+    if all(x==0) && all(y==0)
+        return
+    end
+    
+    if ~isempty(weights) && ~isscalar(weights) && apply_fft
+        img = img .* weights; 
+    end
+    
+    if all(x==0)  % shift only along one axis -> faster 
+        img = utils.imshift_fft_ax(img, y,1, apply_fft);
+    elseif all(y==0)
+        img = utils.imshift_fft_ax(img, x,2, apply_fft);
+    else
+        %%  2D FFT SHIFTING     
+        real_img = isreal(img);
+        Np = size(img);
+
+
+        if apply_fft
+             img = math.fft2_partial(img);
+        end
+
+        xgrid = ifftshift(-fix(Np(2)/2):ceil(Np(2)/2)-1)/Np(2);
+        X = reshape((x(:)*xgrid)',1,Np(2),[]);
+        X =  exp((-2i*pi)*X);
+        img = bsxfun(@times, img,X);
+        ygrid = ifftshift(-fix(Np(1)/2):ceil(Np(1)/2)-1)/Np(1);
+        Y = reshape((y(:)*ygrid)',Np(1),1,[]);
+        Y =  exp((-2i*pi)*Y);
+        img = bsxfun(@times, img,Y);
+
+        if apply_fft
+            img = math.ifft2_partial(img);
+        end
+        if real_img
+            img = real(img);
+        end
+    end
+    
+
+    if ~isempty(weights) && ~isscalar(weights) && apply_fft
+        weights = utils.imshift_fft(weights, x,y);   %% weights needs to be shifted as well
+        img = img ./ weights; 
+    end
+  
+  
+end