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NxtomoLoader
Process categoryBrief description

Computational demand

for typical tomography data

(low, medium, high)

Comment(s)Reference(s)Common alternative process(es)
loaderTo load raw data from input file(s).Uses Low
  1. Employs lazy loading
(see Comment 1).
  1. Data are loaded on the first access request , i. e. the loading of data is delayed until the first genuine access by the next process in the process list ; - loading times depend on data chunking of source dataset(s).
  2. Capable of handling the case of dark- and flat-field images being supplied in datasets stored in individual NeXus datasets.


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


[ ]To load all the entire n-dimensional data located at dataset, stored at location specified by the data_path parameter.Default value.
[:, :, :]To load all 3d data located at the entire 3d data dataset, stored at location specified by the data_path parameter.
[:, s, :] To load from a given 3d dataset only (stored at the data_path location) only a subset of data corresponding to the s-th tomography slice 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 only the data of (stored at data_path location) only a subset of data corresponding to the p-th sample 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 - , :]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 flats from a dataset located at entry1/instrument/detector/pco1/data in a NeXus scan file named /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).If <path-to-NeXus-file> is not None, then flats are loaded from a dataset found at <path-to-dataset> inside the NeXus file located on the file-system at <path-to-NeXus-file>, and their pixel values are then multiplied by <exposure-time-compensation-factor>.
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 darks from a dataset located at entry1/instrument/detector/pco1/data in a NeXus scan file named /dls/i13/data/2018/cm123-4/raw/6.nxs, and then to multiply their pixel values by 1.If <path-to-NeXus-file> is not None, then darks are loaded from a dataset found at <path-to-dataset> inside the NeXus file located on the file-system at <path-to-NeXus-file>, and their pixel values are then multiplied by <exposure-time-compensation-factor>.
8

angles




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.
9

ignore_flats

[ind_1, ind_2,... ind_m][1, r]To ignore the initial and the r-th batch in a series of m batches of flats (each containing however many individual flat-field images).
  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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