Discorpy’s documentation

Discorpy is an open-source Python package for correcting radial distortion with sub-pixel accuracy as required by tomography detector systems [C1]. It is used to calculate parameters of a correction model, which are the center of distortion and the polynomial coefficients, using a grid pattern image. From version 1.4, perspective distortion correction and methods for processing line-pattern and chessboard (checkerboard) images were added to the package.

A key feature of Discorpy is that radial distortion, the center of distortion, and perspective distortion are determined and corrected independently using a single calibration image. Discorpy was developed for calibrating lens-coupled detectors of tomography systems but it also can be used for commercial cameras.

Showcases: https://discorpy.readthedocs.io/en/latest/usage.html#demonstrations

Source code: https://github.com/DiamondLightSource/discorpy

Author: Nghia T. Vo - NSLS-II, Brookhaven National Laboratory, US; Diamond Light Source, UK.

Keywords: Camera calibration, radial lens distortion, perspective distortion, distortion correction, tomography.

Contents

• 1. Installation
  • 1.1. Using conda
  • 1.2. Using pip
  • 1.3. Installing from source
  • 1.4. Using Google Colab
• 2. Tutorials
  • 2.1. Causes of distortion
  • 2.2. Methods for correcting distortions
    • 2.2.1. Introduction
    • 2.2.2. Extracting reference-points from a calibration image
    • 2.2.3. Grouping reference-points into horizontal lines and vertical lines
    • 2.2.4. Calculating the optical center of radial distortion
    • 2.2.5. Correcting perspective effect
    • 2.2.6. Calculating coefficients of a polynomial model for radial-distortion correction
    • 2.2.7. Calculating coefficients of a correction model for perspective distortion
    • 2.2.8. Correcting a distorted image
    • 2.2.9. Summary
• 3. Usage
  • 3.1. Resources
  • 3.2. Notes related to Python programming
  • 3.3. Demonstrations
    • 3.3.1. Process a high-quality calibration image
    • 3.3.2. Process an X-ray target image having perspective effect
    • 3.3.3. Process a challenging X-ray target image
    • 3.3.4. Process a line-pattern image
    • 3.3.5. Correct both radial distortion and perspective distortion
    • 3.3.6. Calibrate a camera using a chessboard image
    • 3.3.7. Correct perspective distortion
    • 3.3.8. Correct radial distortion of an image without using a calibration target
    • 3.3.9. Useful tips
• 4. API reference
  • 4.1. Input-output
    • 4.1.1. discorpy.losa.loadersaver
  • 4.2. Pre-processing
    • 4.2.1. discorpy.prep.preprocessing
    • 4.2.2. discorpy.prep.linepattern
  • 4.3. Processing
    • 4.3.1. discorpy.proc.processing
  • 4.4. Post-processing
    • 4.4.1. discorpy.post.postprocessing
  • 4.5. Utility methods
    • 4.5.1. discorpy.util.utility
• 5. Credit