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+utils/interpolateFT.m

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+% INTERPOLATEFT Computes 2D 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(im,outsize,ax)
+%
+% Inputs:
+%   **im      - Input complex array
+%   **outsize - Output size of array [N pixels]
+%   **ax - index of axis along which interpolation is done 
+%
+% *returns*:
+%   ++imout   - Output complex image
+%
+
+%*-----------------------------------------------------------------------*
+%|                                                                       |
+%|  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(im,outsize)
+import math.fftshift_2D
+import math.ifftshift_2D
+import utils.crop_pad
+
+
+Nout = outsize;
+Nin = size(im);
+
+imFT = fftshift_2D(fft2(im));
+
+imout = crop_pad(imFT, outsize);
+
+imout = ifft2(ifftshift_2D(imout))*(Nout(1)*Nout(2)/(Nin(1)*Nin(2)));
+
+
+
+