3D stereo camera calibration with QT and openCV, using stereo pairs (PNG, TIF, JPG, etc) or stereo MPO images
The present code is under GPL v3 license, that means you can do almost whatever you want
with it!
I used bits of code from several sources, mainly from the openCV examples
I didn't find any simple tool (understand: GUI) to calibrate my lens for stereo photography, because my camera produces MPO files. So why not writing it myself ?
I'm not an ace of C++ and QT, in fact I only started using them some month ago. So, if you don't find my code pretty never mind, because it WORKS, and that's all I'm asking of it :)
Developed using:
- Linux: Ubuntu 16.04
- QT Creator 3.5.1
- QT 5.5.1
- openCV 4.1 compiled with openCV-contribs - should work with 3.x versions without much editing
This software should also work under Microsoft Windows: if you tried it successfully please contact me.
You must first take pictures of checkerboards or circle grids, explained here : https://docs.opencv.org/3.4.1/d4/d94/tutorial_camera_calibration.html
- Select the type of board (openCV-type) you photographed: checkerboard, symmetric or asymmetric circles
- Checkerboard:
- enter the number of inner corners: H x V where H is the number of columns and V the number of rows
- enter the size (in millimeters) of the side length of the squares
- Symmetric circles:
- enter the number of circles: H x V where H is the number of circles per columns and V the number of rows
- enter the size (in millimeters) of the circles diameter
- Asymmetric circles:
- enter the number of circles: H x V where H is the number of circles per columns (it is the same one every row, even if they are shifted) and V the number of rows
- enter the size (in millimeters) of the circles diameter
- Checkerboard:
- Enter your camera’s sensor size (in millimeters)
- Select whether your images are in MPO format or not. openCV accepts many image types like JGP, PNG, TIF…
- Your MPO images must contain two jpegs, forming a stereo pair
- If not using MPO:
- provide 2 files for each stereo pair
- the pair is composed of 2 separate images: first file = LEFT, second file = RIGHT
- of course the total number of files must be EVEN
- Click on the CALIBRATE button:
- Select several image files (with <SHIFT> and <CTRL>)
- The stereo pairs are displayed and processed. If the patterns (checkerboard or circles) are found, they are drawn over the original image
- There are indicators during this first part:
- the blue progress bar represents the overall progress
- the red one shows the images that didn’t match the pattern (the red LED indicator also shows that information)
- the green LED indicator shows the successful patterns found in stereo pairs
- When the overall progress bar reaches 100%, be patient: your camera lens parameters are being computed – it can take a long time, depending on your computer CPUs and the number of successful image pairs (for good results, at least 30 for checkerboards and 15 for circles)
- When the parameters are found:
- a message shows the average errors found for the images, for the left and right lens, AND the stereo pairs
- you will be asked a folder location where you will save the lens parameters, in openCV format (XML and YAML). 3 files will be created: calibration-left, calibration-right and calibration-stereo.xml
The resulting XML files produced by the software will be useful when you want to rectify stereo pairs before computing a depthmap, or find extrinsic values from them. My disparity and depth map filtering utility is avalable here : https://github.com/AbsurdePhoton/disparity-filtering-mpo
My photographer website ''Photongénique'': www.absurdephoton.fr