一、单目校正：
OpenCV provides us with a ready-to-use undistortion algorithm that takes a raw image and the distortion coefficients from cv::calibrateCamera() and produces a corrected image. We can access this algorithm either through the function cv::undistort(), which does everything we need in one shot, or through the pair of routines cv::initUndistortRectifyMap() and cv::remap(), which allow us to handle things a little more efficiently for video or other situations where we have many images from the same camera.也就是，cv::undistort()是一次性的，而cv::initUndistortRectifyMap() and cv::remap()这两个，相当于两步走。
rather than rectifying an entire image, you have a set of points you have collected from an image, and you care only about the location of those points. In this case, you can use cv::undistortPoints() to compute the “correct” locations for your specific list of points也就是，cv::undistortPoints() 用来稀疏校正。
二、双目校正
