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answered May 20 '0
opencv has some means of calibrating cameras, e.g. here or here but you will need the actual camera, it's not possible from images taken later
updated May 20 '0
opencv has some means of calibrating cameras, e.g. here or here but you will need the actual camera, camera (and take images with a known calibration pattern, e.g. a chessboard),
it's not possible from images taken later