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71 lines
3.2 KiB
Matlab
71 lines
3.2 KiB
Matlab
% get vertical and horizontal gradient of the image using FFT
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%
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% [dX, dY] = get_img_grad(img, axis, split)
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%
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% Inputs:
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% **img - stack of images
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% **split - split for GPU fft_partial
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% **axis - direction of the derivative
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% *returns*
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% ++[dX, dY] - image gradients
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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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%
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function [dX, dY] = get_img_grad(img, axis, split)
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import math.*
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if nargin < 3 || isempty(split)
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split = 1;
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end
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isReal = isreal(img);
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Np = size(img);
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if nargin < 2 || any(axis == 2)
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X = 2i*pi*ifftshift(-fix(Np(2)/2):ceil(Np(2)/2)-1)/Np(2);
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dX = bsxfun(@times,fft_partial(img,2,1,split,false),X);
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dX = fft_partial(dX,2,1,split,true);
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if isReal; dX = real(dX);end
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end
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if nargout == 2 || (nargin > 1 && any(axis == 1))
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Y = 2i*pi*ifftshift(-fix(Np(1)/2):ceil(Np(1)/2)-1)/Np(1);
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dY = bsxfun(@times, fft_partial(img,1,2,split,false),Y.');
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dY = fft_partial(dY,1,2,split,true);
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if isReal; dY = real(dY);end
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if nargout == 1; dX = dY; end
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end
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end
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