fisheye_calibrate.py

# from https://medium.com/@kennethjiang/calibrate-fisheye-lens-using-opencv-333b05afa0b0

import cv2
import numpy as np
import glob

assert cv2.__version__[0] == '3', \
    'The fisheye module requires opencv version >= 3.0.0'

CHECKERBOARD = (6, 9)
subpix_criteria = (cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER, 30, 0.1)
calibration_flags = cv2.fisheye.CALIB_RECOMPUTE_EXTRINSIC + \
                    cv2.fisheye.CALIB_CHECK_COND + \
                    cv2.fisheye.CALIB_FIX_SKEW
objp = np.zeros((1, CHECKERBOARD[0] * CHECKERBOARD[1], 3), np.float32)
objp[0, :, :2] = np.mgrid[0:CHECKERBOARD[0],
                          0:CHECKERBOARD[1]].T.reshape(-1, 2)
_img_shape = None
objpoints = []  # 3d point in real world space
imgpoints = []  # 2d points in image plane.

images = glob.glob('*.JPG')
for fname in images:
    img = cv2.imread(fname)
    if _img_shape is None:
        _img_shape = img.shape[:2]
    else:
        assert _img_shape == img.shape[:2], \
            'All images must share the same size.'
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

    # Find the chess board corners
    ret, corners = cv2.findChessboardCorners(
                     gray,
                     CHECKERBOARD,
                     cv2.CALIB_CB_ADAPTIVE_THRESH +
                     cv2.CALIB_CB_FAST_CHECK +
                     cv2.CALIB_CB_NORMALIZE_IMAGE
                   )

    # If found, add object points, image points (after refining them)
    if ret:
        objpoints.append(objp)
        cv2.cornerSubPix(gray, corners, (3, 3), (-1, -1), subpix_criteria)
        imgpoints.append(corners)

N_OK = len(objpoints)
K = np.zeros((3, 3))
D = np.zeros((4, 1))
rvecs = [np.zeros((1, 1, 3), dtype=np.float64) for i in range(N_OK)]
tvecs = [np.zeros((1, 1, 3), dtype=np.float64) for i in range(N_OK)]
rms, _, _, _, _ = \
    cv2.fisheye.calibrate(
        objpoints,
        imgpoints,
        gray.shape[::-1],
        K,
        D,
        rvecs,
        tvecs,
        calibration_flags,
        (cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER, 30, 1e-6)
    )

print("Found " + str(N_OK) + " valid images for calibration")
print("DIM=" + str(_img_shape[::-1]))
print("K=np.array(" + str(K.tolist()) + ")")
print("D=np.array(" + str(D.tolist()) + ")")