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2026-09-17 22:59:07 +09:00 · 2026-08-07 15:56:42 +09:00
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+% INTERPOLATEFT_3D Computes 3D interpolated image using Fourier transform, i.e. dirichlet
+% interpolation. Computes the FT and then adjusts the size by zero padding
+% or cropping then it computes the IFT. A real valued input may have
+% residual imaginary components, which is given by numerical precision of
+% the FT and IFT.
+%
+%  imout = interpolateFT_3D(im,outsize, fourier_mask)
+%
+%   Inputs
+%       **im      - Input real/complex 3D volume
+%       **outsize - Output size of array [ny nx nz]
+%       **fourier_mask - if provided, apply mask in fourier space. ifftn( mask * fftn(im))
+%   *returns*
+%       ++imout   - Output real/complex volume
+
+%*-----------------------------------------------------------------------*
+%|                                                                       |
+%|  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 [ imout ] = interpolateFT_3D(im,outsize, fourier_mask)
+
+Nout = outsize;
+Nin = size(im);
+
+if all(Nout == Nin) && nargin < 3
+    imout = im; 
+    return
+end
+
+
+
+imFT = fftshift(fftn(im));
+
+imout = utils.crop_pad_3D(imFT, outsize);
+
+if nargin > 2
+    % if provided, apply fourier mask, NOT FFTSHIFTED !!
+    imout = imout .* fourier_mask;    
+end
+
+imout = ifftn(ifftshift(imout))*(Nout(1)*Nout(2)*Nout(3)/(Nin(1)*Nin(2)*Nin(3)));
+
+if isreal(im)
+    imout = real(imout); 
+end
+
+
+
+
+