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119 lines
4.2 KiB
Matlab
119 lines
4.2 KiB
Matlab
% INTERPOLATEFT_AX Computes interpolated array using 1D Fourier transform, i.e. dirichlet
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% interpolation along single axis. Computes the FT and then adjusts the size by zero padding
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% or cropping then it computes the IFT. A real valued input may have
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% residual imaginary components, which is given by numerical precision of
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% the FT and IFT.
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%
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% imout = interpolateFT_ax(im,outsize,ax, use_fft)
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%
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% Inputs:
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% **im - Input complex array
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% **outsize - Output size of array [N pixels]
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% **ax - index of axis along which interpolation is done
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% *optional*
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% **use_fft - if false, assume that im is already fft-transformed, default = true
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%
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% Outputs:
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% ++imout - Output complex image
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%
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% Example:
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% x = randn(10,20,30);
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% x_int = utils.interpolateFT_ax(x, 10, 3) % downsample to 10 pixels along 3rd axis
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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 [ imout ] = interpolateFT_ax(im,outsize,ax, use_fft)
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Nin = size(im);
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if ax > ndims(im)
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Nin(ax) = 1;
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end
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if nargin < 4
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use_fft = true;
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end
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Nout = Nin;
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Nout(ax) = outsize;
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if use_fft
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imFT = fft(im,[],ax);
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else
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imFT = im;
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end
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centerin = floor(Nin(ax)/2)+1;
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centerout = floor(Nout(ax)/2)+1;
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center_diff = centerout - centerin;
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grid_in = fftshift(1:Nin(ax));
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grid_in = grid_in(max(-center_diff+1,1):min(-center_diff+Nout(ax),Nin(ax)));
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grid_in = {grid_in,':',':',':'};
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grid_in = circshift( grid_in, ax-1);
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grid_out = [max(ceil(Nout(ax)/2)+1,Nout(ax) - centerin+2):Nout(ax), ...
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1:min(centerin-1, ceil(Nout(ax)/2))];
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grid_out = {grid_out,':',':',':'};
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grid_out = circshift( grid_out, ax-1);
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if Nout(ax) > Nin(ax)
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% perform multiplication to keep average values,
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% multiply the smaller array to save time
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imFT = imFT*(Nout(ax)/(Nin(ax)));
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end
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imout = zeros(Nout,'like',im);
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imout(grid_out{:}) = imFT(grid_in{:});
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if use_fft
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imout = ifft(imout,[],ax);
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end
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if Nout(ax) < Nin(ax)
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% perform multiplication to keep average values,
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% multiply the smaller array to save time
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imout = imout*(Nout(ax)/(Nin(ax)));
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end
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end
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