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% -----------------------------------------------------------------------
% This file is part of the ASTRA Toolbox
%
% Copyright: 2010-2018, imec Vision Lab, University of Antwerp
% 2014-2018, CWI, Amsterdam
% License: Open Source under GPLv3
% Contact: astra@astra-toolbox.com
% Website: http://www.astra-toolbox.com/
% -----------------------------------------------------------------------
% This example demonstrates using the FP and BP primitives with Matlab's lsqr
% solver. Calls to FP (astra_create_sino_cuda) and
% BP (astra_create_backprojection_cuda) are wrapped in a function astra_wrap,
% and a handle to this function is passed to lsqr.
% Because in this case the inputs/outputs of FP and BP have to be vectors
% instead of images (matrices), the calls require reshaping to and from vectors.
function s015_fp_bp
% FP/BP wrapper function
function Y = astra_wrap(X,T)
if strcmp(T, 'notransp')
% X is passed as a vector. Reshape it into an image.
[sid, s] = astra_create_sino_cuda(reshape(X,[vol_geom.GridRowCount vol_geom.GridColCount])', proj_geom, vol_geom);
astra_mex_data2d('delete', sid);
% now s is the sinogram. Reshape it back into a vector
Y = reshape(s',[prod(size(s)) 1]);
else
% X is passed as a vector. Reshape it into a sinogram.
v = astra_create_backprojection_cuda(reshape(X, [proj_geom.DetectorCount size(proj_geom.ProjectionAngles,2)])', proj_geom, vol_geom);
% now v is the resulting volume. Reshape it back into a vector
Y = reshape(v',[prod(size(v)) 1]);
end
end
vol_geom = astra_create_vol_geom(256, 256);
proj_geom = astra_create_proj_geom('parallel', 1.0, 384, linspace2(0,pi,180));
% Create a 256x256 phantom image using matlab's built-in phantom() function
P = phantom(256);
% Create a sinogram using the GPU.
[sinogram_id, sinogram] = astra_create_sino_gpu(P, proj_geom, vol_geom);
% Reshape the sinogram into a vector
b = reshape(sinogram',[prod(size(sinogram)) 1]);
% Call Matlab's lsqr with ASTRA FP and BP
Y = lsqr(@astra_wrap,b,1e-4,25);
% Reshape the result into an image
Y = reshape(Y,[vol_geom.GridRowCount vol_geom.GridColCount])';
imshow(Y,[]);
astra_mex_data2d('delete', sinogram_id);
end
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