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ItemParameter nameParameter formatExample(s)Comment(s)
Parameter valueEffect
1preview[ind_0, ind_1,... ind_(n-1)]


[ ]To load the entire n-dimensional dataset, stored at location specified by the data_path parameter.Empty Python list, [ ], is the default value of the preview parameter.
[:, :, :]To load the entire 3d dataset, stored at location specified by the data_path parameter.
[:, s, :] To load from a given 3d dataset (stored at the data_path location) only a subset of data corresponding to the s-th sinogram.This particular interpretation applies if data are laid out in the (angle_enumeration, image_height, image_width) format.
[p, :, :]To load from a given 3d dataset (stored at data_path location) only a subset of data corresponding to the p-th projection.This particular interpretation applies if data are laid out in the (angle_enumeration, image_height, image_width) format.
[:, :, 123:-123]To load from a given 3d dataset (stored at the data_path location) only a subset of data generated by cropping the width of each projection by 123 pixels on either side.This particular interpretation applies if data are laid out in the (angle_enumeration, image_height, image_width) format.
[:, mid - 1:mid + 1, :]To load from a given 3d dataset (stored at the data_path location) only a subset of data corresponding to the middle 2 sinograms.mid is one of Savu keywords (with an obvious meaning).
[0:end:2, :, :]To load from a given 3d dataset (stored at the data_path location) only a subset of data corresponding to every other projection.end is one of Savu keywords (with an obvious meaning).
[:, 0:end:2, :]To load from a given 3d dataset (stored at the data_path location) only a subset of data corresponding to every other sinogram.
2

image_key_path




Mandatory dataset.
3

name





4

3d_to_4d





5

flat

[<path-to-NeXus-file>, <path-to-dataset>, <exposure-time-compensation-factor>][/dls/i13/data/2018/cm123-4/raw/5.nxs, entry1/instrument/detector/pco1/data, 1.25]To load all flats from the flats-only dataset found at entry1/instrument/detector/pco1/data inside a NeXus scan file, located on the file system at /dls/i13/data/2018/cm123-4/raw/5.nxs, and then to multiply their pixel values by 1.25 (to compensate for the flat-field exposure time being 0.8 times shorter than the sample-projection exposure time).
  1. Specify this parameter only if flats are not stored in the same dataset as sample projections.
  2. If <path-to-NeXus-file> is not None, then flats are loaded from a dataset found at <path-to-dataset> inside a NeXus file, located on the file-system at <path-to-NeXus-file>, and their pixel values are then multiplied by <exposure-time-compensation-factor>.
  3. No image-key information is required to accompany the flat dataset, and, if present (at the location specified by image_key_path), this information is ignored.
  4. Note that, if the flat-field dataset is integer-valued, then the multiplication by <exposure-time-compensation-factor> (even if the latter is equal to 1) changes this data type to the floating-point type, which in turn may be unsuitable as input for the immediately succeeding process, e.g. Dezinger (use DezingerSinogram instead).
6

data_path




Mandatory dataset.
7

dark

[<path-to-NeXus-file>, <path-to-dataset>, <exposure-time-compensation-factor>][/dls/i13/data/2018/cm123-4/raw/6.nxs, entry1/instrument/detector/pco1/data, 1]To load all darks from the darks-only dataset found at entry1/instrument/detector/pco1/data inside a NeXus scan file, located on the file system at /dls/i13/data/2018/cm123-4/raw/6.nxs, and then to multiply their pixel values by 1 (no change to intensities).
  1. Specify this parameter only if darks are not stored in the same dataset as sample projections.
  2. If <path-to-NeXus-file> is not None, then darks are loaded from a dataset found at <path-to-dataset> inside a NeXus file, located on the file-system at <path-to-NeXus-file>, and their pixel values are then multiplied by <exposure-time-compensation-factor>.
  3. No image-key information is required to accompany the dark dataset, and, if present (at the location specified by image_key_path), this information is ignored.
  4. Note that, if the dark-field dataset is integer-valued, then the multiplication by <exposure-time-compensation-factor> (even if the latter is equal to 1) changes this data type to the floating-point type, which in turn may be unsuitable as input for the immediately succeeding process, e.g. Dezinger (use DezingerSinogram instead).
8

angles


None (Python keyword)If the angles parameter is set to None, then this loader attempts to find them in a default dataset, located at entry1/tomo_entry/data/rotation_angle in the input NeXus scan file.
numpy.linspace(0,180,1801)
Code Block
array([  0.00000000e+00,   1.00000000e-01,   2.00000000e-01, ...,
         1.79800000e+02,   1.79900000e+02,   1.80000000e+02])

9

ignore_flats

[ind_1, ind_2,... ind_m][1, r]To ignore the initial and the r-th batch in a given series of batches of flats (each containing however many individual flat-field images), stored in the same dataset as darks and sample projections.
  1. Useful for excluding compromised flats for scans containing multiple batches of mid-scan flats.
  2. In the ignore_flats list, batch indexing starts from 1 (not 0).

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