def _sample_FDK_(projections, geometry, sample):
'''
Compute a subsampled version of FDK
'''
geometry_ = geometry.copy()
projections_ = projections[::sample[0], ::sample[2], ::sample[2]]
# Apply subsampling to detector and volume:
vol_sample = [sample[0], sample[1], sample[2]]
det_sample = [sample[0], sample[2], sample[2]]
geometry_['vol_sample'] = vol_sample
geometry_['det_sample'] = det_sample
volume = projector.init_volume(projections_)
# Do FDK without progress_bar:
projector.settings.progress_bar = False
projector.FDK(projections_, volume, geometry_)
projector.settings.progress_bar = True
return volume
# Initialize images:
proj_a = numpy.zeros([128, 32, 128], dtype='float32')
proj_b = numpy.zeros([128, 32, 128], dtype='float32')
# Forward project:
projector.forwardproject(proj_a, vol, geom_a)
projector.forwardproject(proj_b, vol, geom_b)
display.slice(proj_a, dim=1, title='Proj A')
display.slice(proj_b, dim=1, title='Proj B')
#%% Preview reconstructions:
geom_b = geom_a.copy()
# First volume:
vola = projector.init_volume(proj_a)
projector.FDK(proj_a, vola, geom_a)
# Second volume:
volb = projector.init_volume(proj_b)
projector.FDK(proj_b, volb, geom_b)
display.projection(vola, dim=1, title='Volume A')
display.projection(volb, dim=1, title='Volume B')
#%% Register:
R, T = process.register_volumes(vola,
volb,
subsamp=1,
use_moments=True,
use_CG=True)
vol = phantom.cuboid([128, 128, 128], geom, 3, 3, 3)
display.slice(vol, title='Phantom')
# Forward project:
projector.forwardproject(proj, vol, geom)
display.slice(proj, dim=1, title='Projection')
#%% Use optimize_rotation_center:
# Unmodified geometry:
geom = geometry.circular(src2obj=100,
det2obj=100,
det_pixel=0.1,
ang_range=[0, 360])
vol = projector.init_volume(proj)
projector.FDK(proj, vol, geom)
display.slice(vol, bounds=[0, 2], title='FDK: uncorrected')
#%% Optimization:
vals = numpy.linspace(0., 3., 7)
process.optimize_modifier(vals,
proj,
geom,
samp=[1, 1, 1],
key='det_roll',
metric='highpass')
#%% Reconstruct: