Measuring with computer vision
- You need a QR code (can be empty, don't matters what it contain).
- Mine was 5 cm (500 millimeters).
- You can select by pressing "s" and confirm by pressing "space" or "enter".
Original QR Reader: https://www.pyimagesearch.com/2018/05/21/an-opencv-barcode-and-qr-code-scanner-with-zbar/