OpenCV: ChArUco camera calibration

calibrate.py

# https://docs.opencv.org/4.x/da/d13/tutorial_aruco_calibration.html
# data: https://drive.google.com/file/d/12IWsHiERr0xGrcAPe9VCkWNMrqEmI3fF/view?usp=drive_link
import cv2 as cv
import os

aruco_dict = cv.aruco.getPredefinedDictionary(cv.aruco.DICT_6X6_100)
board = cv.aruco.CharucoBoard((5, 7),
                              squareLength=110,
                              markerLength=72,
                              dictionary=aruco_dict)
detector = cv.aruco.CharucoDetector(board)

obj_points = []
img_points = []
for path in os.listdir("images"):
    img = cv.imread(f"images\\{path}")

    corners, charucoIds, _, _ = detector.detectBoard(img)

    #cv.aruco.drawDetectedCornersCharuco(img, corners, charucoIds=charucoIds)
    #cv.imwrite(f"debug\\{path}.jpg", img)

    if corners is not None and len(corners) > 0:
        frame_obj_points, frame_img_points = board.matchImagePoints(corners, charucoIds)
        if len(frame_obj_points) > 4:
            obj_points.append(frame_obj_points)
            img_points.append(frame_img_points)

print("Start calibration")
rms, camera_matrix, dist_coefs, _, _ = cv.calibrateCamera(obj_points,
                                                          img_points,
                                                          (960, 1280),
                                                          None,
                                                          None)
print(rms)
print(camera_matrix)
print(dist_coefs)

detect_and_draw.py

# https://github.com/opencv/opencv/blob/4.x/samples/python/aruco_detect_board_charuco.py
import numpy as np
import cv2 as cv

aruco_dict = cv.aruco.getPredefinedDictionary(cv.aruco.DICT_6X6_100)
board = cv.aruco.CharucoBoard((5, 7), squareLength=0.035, markerLength=0.023, dictionary=aruco_dict)
detector = cv.aruco.CharucoDetector(board)

img = cv.imread("images\\2.jpg")

corners, charucoIds, markerCorners, markerIds = detector.detectBoard(img)
cv.aruco.drawDetectedMarkers(img, markerCorners)
cv.aruco.drawDetectedCornersCharuco(img, corners)

frame_obj_points, frame_img_points = board.matchImagePoints(corners, charucoIds)

camera_matrix = np.array([[984.68630771,   0.,         479.32526648],
 [  0.,         985.07648021, 642.04072255],
 [  0.,           0.,           1.        ]])

dist_coeffs = np.array([[ 1.40327092e-01,-7.56241483e-01 ,1.12768928e-03,-4.88750897e-04, 1.31331599e+00]])
_, rvec, tvec = cv.solvePnP(frame_obj_points, frame_img_points, camera_matrix, dist_coeffs)

cv.drawFrameAxes(img, camera_matrix, dist_coeffs, rvec, tvec, length=0.035 * 3, thickness=3)

cv.imwrite("debug\\axes.jpg", img)

gen_board.py

# https://docs.opencv.org/4.x/df/d4a/tutorial_charuco_detection.html
import cv2 as cv

cols = 5
rows = 7
squareLength = 100
markerLength = 65
margin = squareLength - markerLength

aruco_dict = cv.aruco.getPredefinedDictionary(cv.aruco.DICT_6X6_100)
board = cv.aruco.CharucoBoard((cols, rows), squareLength=squareLength, markerLength=markerLength, dictionary=aruco_dict)
img = board.generateImage((cols*squareLength + 2 * margin, rows*squareLength + 2 * margin), margin)
cv.imwrite("img.png", img)