Discorpy

(Dis)tortion (Cor)rection (Py)thon-package

Distortion calibration and correction software for lens-based detector systems

Discorpy is an open-source Python package for distortion correction with sub-pixel accuracy as required by tomography detector systems. It calculates parameters of correction models using a grid pattern image. The package implements methods published by Nghia T. Vo et al. "Radial lens distortion correction with sub-pixel accuracy for X-ray micro- tomography," Optics Express, 23, 32859-32868 (2015), https://doi.org/10.1364/OE.23.032859. From version 1.4, correction for perspective distortion has been added to the package.

Author: Nghia Vo, Diamond Light Source, UK.

Update notes

• 25/02/2021: the package name is changed from Vounwarp to Discorpy. The old-name package is still available at https://github.com/nghia-vo/vounwarp and installable using conda-forge channel: https://anaconda.org/conda-forge/vounwarp
• 21/11/2021: Correction for perspective distortion, pre-processing methods for line-pattern images and chessboard images are added to the package.

Features

• Pre-processing methods for: extracting reference-points from a dot-pattern image, line-pattern image, and chessboard image; grouping these points line-by-line.
• Processing methods for calculating the optical center, coefficients of polynomial models for correcting radial distortion, and parameters of a model for correcting perspective distortion.
• Post-processing methods for: undistorting lines of points, images, or slices of a 3D dataset; and evaluating the accuracy of the correction results.
• Some methods may be useful for other applications:
  • Correct non-uniform background using a FFT-based filter and a median filter.
  • Select binary objects in a certain range of values.
  • Unwarp slices of a 3D dataset.

Documentation

• https://discorpy.readthedocs.io/en/latest/

Installation

• https://discorpy.readthedocs.io/en/latest/install.html

How to use

• https://discorpy.readthedocs.io/en/latest/usage.html

Demonstrations

• Apply to a visible dot-target collected at Beamline I12, Diamond Light Source, UK:

  

  

• Apply to an X-ray dot-target collected at Beamline I13, Diamond Light Source, UK:

  

  

• Improvement of a tomographic reconstructed image after distortion correction.

  • Before the correction:

    

  • After the correction:

    

• Apply to a hazard camera of the Mars Perseverance Rover. Details of how to estimate distortion coefficients of that camera without using a calibration target are shown here