This repository provides a Python script for getting camera intrinsics and extrinsics parameters using patterned images.
OpenCV functions are used to detect checkerboard corners and get camera intrinsics and extrinsics parameters. The procedure is explained in [1].
The MATLAB function, ./algorithm/matlab/calib_with_matlab.m, is called from a python script and used to do the checkerboard detection and camera calibration. See [2].
This is a Python implementation built from scratch based on the original paper of Zhang [3]. Intrinsics and extrinsics parameters are determined as closed form solutions of equations. As an option, it is possible to optimize the determined camera parameters by minimizing reprojection error.
The main.py code is very simple as shown below:
Once you specify the CONFIG dictionary, you can simply run this code to calibrate a camera. Please note that all input images should contain a checkerboard with good visibility and be stored in the ./data folder.
By using this tool, intrinsics and extrinsics parameters of a camera can be obtained. The extrinsics parameters can be determined for each image.
Example data, which are images of a printed checkerboard pattern generated from [4], are provided in the ./data folder.
In order to interpret the extrinsic parameters better, X and Y axes with a coordinate origin can be visualized together with detected checkerboard corners.
In addition, reprojection error can be also calculated in order to quantitatively assess the quality of the determined camera calibration parameters.
[1] OpenCV, Camera Calibration, opencv.org [Online]. Available: https://docs.opencv.org/4.x/dc/dbb/tutorial_py_calibration.html [Accessed: 01 January, 2024]
[2] MathWorks, estimateCameraParameters, mathworks.com [Online]. Available: https://mathworks.com/help/vision/ref/estimatecameraparameters.html [Accessed: 01 Januarry, 2024]
[3] Z. Zhang, “A Flexible New Technique for Camera Calibration.” IEEE Transactions on Pattern Analysis and Machine Intelligence. vol. 22, no. 11, pp. 1330–1334, 2000.
[4] calib.io, Pattern Generator, calib.io [Online]. Available: https://calib.io/pages/camera-calibration-pattern-generator [Accessed: 02 January, 2024]
[5] MathWorks, What Is Camera Calibration, mathworks.com [Online]. Available: https://mathworks.com/help/vision/ug/camera-calibration.html [Accessed: 02 January, 2024]