For a single image, you'd need some heuristics to distinguish curved objects from camera distortions. If you have multiple frames, you can SLAM your way out of

For a single image, you'd need some heuristics to distinguish curved objects from camera distortions. If you have multiple frames, you can SLAM your way out of the problem (essentially, match features and solve a big fit which optimized feature positions, camera positions and camera distortions). But by far the easiest option is to just calibrate it, through https://docs.opencv.org/4.x/dc/dbb/tutorial_py_calibration.html https://docs.opencv.org/4.x/dc/dbb/tutorial_py_calibration.h... or one of the many alternative methods.