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https://github.com/c-sooyoung/fold_slice.git
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84 lines
3.6 KiB
Matlab
84 lines
3.6 KiB
Matlab
% IMRESCALE_FFT subpixel precision rescaling based on multiplication by a
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% matrix of fourier transformation, fast only for small arrays
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% Inputs:
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% **img - 2D or stack of 2D images
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% **scale - scaling factor
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% *returns*:
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% ++img - 2D or stack of 2D images scaled by factor scale
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%*-----------------------------------------------------------------------*
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%| |
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%| Except where otherwise noted, this work is licensed under a |
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%| Creative Commons Attribution-NonCommercial-ShareAlike 4.0 |
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%| International (CC BY-NC-SA 4.0) license. |
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%| |
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%| Copyright (c) 2017 by Paul Scherrer Institute (http://www.psi.ch) |
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%| |
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%| Author: CXS group, PSI |
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%*-----------------------------------------------------------------------*
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% You may use this code with the following provisions:
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%
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% If the code is fully or partially redistributed, or rewritten in another
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% computing language this notice should be included in the redistribution.
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%
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% If this code, or subfunctions or parts of it, is used for research in a
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% publication or if it is fully or partially rewritten for another
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% computing language the authors and institution should be acknowledged
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% in written form in the publication: “Data processing was carried out
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% using the “cSAXS matlab package” developed by the CXS group,
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% Paul Scherrer Institut, Switzerland.”
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% Variations on the latter text can be incorporated upon discussion with
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% the CXS group if needed to more specifically reflect the use of the package
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% for the published work.
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%
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% A publication that focuses on describing features, or parameters, that
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% are already existing in the code should be first discussed with the
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% authors.
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%
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% This code and subroutines are part of a continuous development, they
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% are provided “as they are” without guarantees or liability on part
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% of PSI or the authors. It is the user responsibility to ensure its
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% proper use and the correctness of the results.
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function img_rescale = imrescale_fft(img, scale)
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if scale == 1 || isnan(scale)
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img_rescale = img;
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return
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end
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N = size(img);
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for i = 1:2
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if N(1) ~= N(2) || i == 1
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ind_x = real(zeros(N(i),1, 'like', img));
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ind_x(:) = (0:N(i)-1)/N(i)-0.5;
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grid = ind_x*ind_x';
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grid = -2i*pi*N(i)/scale*grid;
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W{i} = exp(grid)'/N(i); % matrix of fourier transformation
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else
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W{2} = W{1};
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end
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end
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fimg = fftshift(fft2(fftshift(img)));
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if size(img,3) > 1
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fimg2 = W{1}*reshape(fimg,N(1),[]);
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fimg2 = reshape(fimg2, N(1),N(2),[]);
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fimg2 = permute(fimg2, [2,1,3]);
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fimg2 = reshape(fimg2, N(2),[]);
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img_rescale = (W{1}*fimg2); % rescale and fft back
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img_rescale = reshape(img_rescale, N(2),N(1),[]);
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img_rescale = permute(img_rescale, [2,1,3]);
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else
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fimg2 = W{1}*fimg;
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img_rescale = (W{2}*fimg2.').';
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end
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end
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