Single camera calibration using OpenCV

camera_calibration.py

#!/usr/bin/env python3

# input video file:
input_file = 'input_video.mp4'

# termination criteria
criteria = (cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER, 30, 0.001)

# change this to your checkerboard dimensions:
width_number_of_squares = 14
height_number_of_squares = 9

# change this to own preference:
numer_of_calibration_images = 200

# prepare object points, like (0,0,0), (1,0,0), (2,0,0) ....,(6,5,0)
objp = np.zeros((height_number_of_squares*width_number_of_squares,3), np.float32)
objp[:,:2] = np.mgrid[0:width_number_of_squares,0:height_number_of_squares].T.reshape(-1,2)

# Arrays to store object points and image points from all the images.
objpoints = [] # 3d point in real world space
imgpoints = [] # 2d points in image plane.

# initiate video capture
cap = cv2.VideoCapture(input_file)
frame_idx = 0
calibration_images = 0

# create empty window
cv2.namedWindow('img',cv2.WINDOW_NORMAL)

while(cap.isOpened()):
    ret, img = cap.read()
    if calibration_images >= numer_of_calibration_images:
        print('frame count: ',frame_idx)
        break
    if ret == True:
        gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

        # Find the chess board corners
        check_ret, corners = cv2.findChessboardCornersSB(gray, (width_number_of_squares,height_number_of_squares),None)

        # If found, add object points, image points (after refining them)
        if check_ret == True:
            objpoints.append(objp)

            corners2 = cv2.cornerSubPix(gray,corners,(11,11),(-1,-1),criteria)
            imgpoints.append(corners2)
            calibration_images += 1 
            
            # Draw and display the corners
            img = cv2.drawChessboardCorners(img, (width_number_of_squares,height_number_of_squares), corners2, check_ret)
        
        cv2.imshow('img',img)
        
        # close window by pressing 'q'
        if cv2.waitKey(1) & 0xFF == ord('q'):
            cv2.destroyAllWindows()
            break
        if frame_idx % 5 == 0:
            print('frame count: ',frame_idx)
        frame_idx += 1
    else:
        continue
    
cv2.destroyAllWindows()

ret, mtx, dist, rvecs, tvecs = cv2.calibrateCamera(objpoints, imgpoints, gray.shape[::-1],None,None)

print(ret, mtx, dist, rvecs, tvecs)
print('Finished calibration!')