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+%------------------------------------------------------------------------
+% This file is part of the
+% All Scale Tomographic Reconstruction Antwerp Toolbox ("ASTRA-Toolbox")
+%
+% Copyright: iMinds-Vision Lab, University of Antwerp
+% License: Open Source under GPLv3
+% Contact: mailto:astra@ua.ac.be
+% Website: http://astra.ua.ac.be
+%------------------------------------------------------------------------
+
+
+% 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