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+utils/imshift_linear_ax.m

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+% IMSHIFT_LINEAR_AX  will apply shift that can be different for 
+%     each frame along axis ax   
+%     + compared to imshift_fft, it does not have periodic boundary 
+%     + it is based on linear interpolation, so it can be run fast on GPU 
+%     + integer shift is equivalent to imshift_fft (up to the boundary condition)
+%     - it needs for-loop for each frame -> it gets slow on GPU for
+%       shifting my small images. In that case imshift_fft can be faster. 
+%
+%   img = imshift_linear(img, x,y, method)
+%
+%   Inputs:
+%       **img       input image / stack of images 
+%       **shift     applied shift or vector of shifts for each frame 
+%       **ax        axis along which the shift will be performed 
+%       **method    choose interpolation method: nearest, {linear}, cubic , circ
+%       **extrap_val filling value for the missing regions after interpolation (default=nan)
+% 
+%   returns: 
+%       ++img        shifted image / stack of images 
+%
+%  see also: utils.imshift_fast, utils.imshift_fft
+
+
+
+
+%*-----------------------------------------------------------------------*
+%|                                                                       |
+%|  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_out = imshift_linear_ax(img, shift, ax, method, extrap_val)
+
+
+    if nargin < 4
+        method = 'linear';
+    end
+    if nargin < 5
+        extrap_val = nan; 
+    end
+        
+    if all(shift == 0)
+        img_out=img;
+        return
+    end
+        
+    Npix = size(img);
+    
+    img = single(img);
+    
+    img = shiftdim(img, ax-1);
+
+    img_out = img; 
+  
+    
+    ind = {':',':',':'}; % assume max 3 dim 
+    ax_0 = 1+mod(ax,ndims(img)); % fixed axis 
+    
+    if strcmpi(method, 'circ')
+        % apply NN shift with circular condition 
+        for i = 1:Npix(ax_0)
+            ind{ax_0} = i;      
+            img_out(ind{:}) = circshift(img(ind{:}), round(shift(i)), ax);
+        end
+    else
+        
+        for ii = 1:Npix(ax_0)
+            ind{ax_0} = ii;      
+            img_out(ind{:}) = interp1(1:size(img,1), img(ind{:}), -shift(ii)+(1:size(img,1)), method, extrap_val);
+        end
+    
+    end
+    
+    img_out = shiftdim(img_out, ax-1);
+    
+  
+  
+end