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% -----------------------------------------------------------------------
% This file is part of the ASTRA Toolbox
%
% Copyright: 2010-2016, iMinds-Vision Lab, University of Antwerp
% 2014-2016, CWI, Amsterdam
% License: Open Source under GPLv3
% Contact: astra@uantwerpen.be
% Website: http://www.astra-toolbox.com/
% -----------------------------------------------------------------------
% In this example we will create a reconstruction in a circular region,
% instead of the usual rectangle.
% This is done by placing a circular mask on the square reconstruction volume:
c = -127.5:127.5;
[x y] = meshgrid(-127.5:127.5,-127.5:127.5);
mask = (x.^2 + y.^2 < 127.5^2);
figure(1); imshow(mask, []);
vol_geom = astra_create_vol_geom(256, 256);
proj_geom = astra_create_proj_geom('parallel', 1.0, 384, linspace2(0,pi,50));
% As before, create a sinogram from a phantom
P = phantom(256);
[sinogram_id, sinogram] = astra_create_sino_gpu(P, proj_geom, vol_geom);
figure(2); imshow(P, []);
figure(3); imshow(sinogram, []);
% Create a data object for the reconstruction
rec_id = astra_mex_data2d('create', '-vol', vol_geom);
% Create a data object for the mask
mask_id = astra_mex_data2d('create', '-vol', vol_geom, mask);
% Set up the parameters for a reconstruction algorithm using the GPU
cfg = astra_struct('SIRT_CUDA');
cfg.ReconstructionDataId = rec_id;
cfg.ProjectionDataId = sinogram_id;
cfg.option.ReconstructionMaskId = mask_id;
% Create the algorithm object from the configuration structure
alg_id = astra_mex_algorithm('create', cfg);
% Run 150 iterations of the algorithm
astra_mex_algorithm('iterate', alg_id, 150);
% Get the result
rec = astra_mex_data2d('get', rec_id);
figure(4); imshow(rec, []);
% Clean up. Note that GPU memory is tied up in the algorithm object,
% and main RAM in the data objects.
astra_mex_algorithm('delete', alg_id);
astra_mex_data2d('delete', mask_id);
astra_mex_data2d('delete', rec_id);
astra_mex_data2d('delete', sinogram_id);
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