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# -----------------------------------------------------------------------
# Copyright: 2010-2018, imec Vision Lab, University of Antwerp
# 2013-2018, CWI, Amsterdam
#
# Contact: astra@astra-toolbox.com
# Website: http://www.astra-toolbox.com/
#
# This file is part of the ASTRA Toolbox.
#
#
# The ASTRA Toolbox is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# The ASTRA Toolbox is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with the ASTRA Toolbox. If not, see <http://www.gnu.org/licenses/>.
#
# -----------------------------------------------------------------------
import astra
import numpy as np
cor_shift = 3.6
vol_geom = astra.create_vol_geom(256, 256)
proj_geom = astra.create_proj_geom('parallel', 1.0, 256, np.linspace(0,np.pi,180,False))
# Projection geometry with shifted center of rotation
proj_geom_cor = astra.geom_postalignment(proj_geom, cor_shift)
# As before, create a sinogram from a phantom, using the shifted center of rotation
import scipy.io
P = scipy.io.loadmat('phantom.mat')['phantom256']
proj_id_cor = astra.create_projector('cuda',proj_geom_cor,vol_geom)
sinogram_id, sinogram = astra.create_sino(P, proj_id_cor)
# Change the projection geometry metadata attached to the sinogram to standard geometry,
# and try to do a reconstruction, to show the misalignment artifacts caused by
# the shifted center of rotation
astra.data2d.change_geometry(sinogram_id, proj_geom)
import pylab
pylab.gray()
pylab.figure(1)
pylab.imshow(P)
pylab.figure(2)
pylab.imshow(sinogram)
# Create a data object for the reconstruction
rec_id = astra.data2d.create('-vol', vol_geom)
# Set up the parameters for a reconstruction algorithm using the GPU
cfg = astra.astra_dict('FBP_CUDA')
cfg['ReconstructionDataId'] = rec_id
cfg['ProjectionDataId'] = sinogram_id
alg_id = astra.algorithm.create(cfg)
astra.algorithm.run(alg_id)
# Get the result
rec = astra.data2d.get(rec_id)
pylab.figure(3)
pylab.imshow(rec)
astra.algorithm.delete(alg_id)
astra.data2d.delete(rec_id)
# Now change back to the proper, shifted geometry, and do another reconstruction
astra.data2d.change_geometry(sinogram_id, proj_geom_cor)
rec_id = astra.data2d.create('-vol', vol_geom)
cfg = astra.astra_dict('FBP_CUDA')
cfg['ReconstructionDataId'] = rec_id
cfg['ProjectionDataId'] = sinogram_id
alg_id = astra.algorithm.create(cfg)
astra.algorithm.run(alg_id)
# Get the result
rec = astra.data2d.get(rec_id)
pylab.figure(4)
pylab.imshow(rec)
pylab.show()
astra.data2d.delete(sinogram_id)
astra.projector.delete(proj_id_cor)
astra.algorithm.delete(alg_id)
astra.data2d.delete(rec_id)
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