FP

This is a CPU implementation of a simple forward projection algorithm for 2D data sets. It takes a projector and a volume as input, and returns the projection data.

Supported geometries: parallel, parallel_vec, fanflat, fanflat_vec, matrix.

Configuration options

Name	Description
ProjectorId	Projector object ID.
ProjectionDataId	Data object ID to store the result. The computed forward projection is added to this data.
VolumeDataId	Volume data object ID.
option.SinogramMaskId	If specified, data object ID of a projection-data-sized volume to be used as a mask.
option.VolumeMaskId	If specified, the data object ID of a volume-data-sized volume to be used as a mask.

Example

import astra
import matplotlib.pyplot as plt
import numpy as np

# Create geometries and projector
N = 256
N_ANGLES = 180
det_spacing = 1.0
angles = np.linspace(0, np.pi, N_ANGLES)
proj_geom = astra.create_proj_geom('parallel', det_spacing, N, angles)
vol_geom = astra.create_vol_geom(N, N)
projector_id = astra.create_projector('linear', proj_geom, vol_geom)

# Generate phantom image
phantom_id, phantom = astra.data2d.shepp_logan(vol_geom)

# Calculate forward projection
projection_id = astra.data2d.create('-sino', proj_geom)
cfg = astra.astra_dict('FP')
cfg['ProjectorId'] = projector_id
cfg['ProjectionDataId'] = projection_id
cfg['VolumeDataId'] = phantom_id
algorithm_id = astra.algorithm.create(cfg)

astra.algorithm.run(algorithm_id)

projection = astra.data2d.get(projection_id)
plt.imshow(projection, cmap='gray')

# Clean up
astra.data2d.delete([projection_id, phantom_id])
astra.projector.delete(projector_id)
astra.algorithm.delete(algorithm_id)

%% Create phantom
N = 256;
phantom = phantom(N);

%% Create geometries and projector
det_spacing = 1.0;
N_ANGLES = 180;
angles = linspace(0, pi, N_ANGLES);
proj_geom = astra_create_proj_geom('parallel', det_spacing, N, angles);
vol_geom = astra_create_vol_geom(N, N);
projector_id = astra_create_projector('linear', proj_geom, vol_geom);

%% Calculate forward projection
phantom_id = astra_mex_data2d('create', '-vol', vol_geom, phantom);
projection_id = astra_mex_data2d('create', '-sino', proj_geom);
cfg = astra_struct('FP');
cfg.ProjectorId = projector_id;
cfg.ProjectionDataId = projection_id;
cfg.VolumeDataId = phantom_id;
algorithm_id = astra_mex_algorithm('create', cfg);

astra_mex_algorithm('run', algorithm_id);

projection = astra_mex_data2d('get', projection_id);
imshow(projection, []);

%% Clean up
astra_mex_data2d('delete', phantom_id, projection_id);
astra_mex_projector('delete', projector_id);
astra_mex_algorithm('delete', algorithm_id);