The distortion I'm aiming to correct is not from the lens but from a qr code posted on a cylindrical surface ( e.g. qr code posted on lampost), with an unknown radius. So ( at least by my understanding) there's no parameters? So my input would be a distorted qr code image and the output from the trained network would be the predicted qr code image without distortion. Am I wrong in my approach/way of thinking?