cameraCalibration.py

#https://aliyasineser.medium.com/opencv-camera-calibration-e9a48bdd1844

import numpy as np
import cv2
import glob
import argparse

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


def calibrate(dirpath, prefix, image_format, square_size, width=9, height=6):
    """ Apply camera calibration operation for images in the given directory path. """
    # prepare object points, like (0,0,0), (1,0,0), (2,0,0) ....,(8,6,0)
    objp = np.zeros((height*width, 3), np.float32)
    objp[:, :2] = np.mgrid[0:width, 0:height].T.reshape(-1, 2)

    objp = objp * square_size

    # 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.

    if dirpath[-1:] == '/':
        dirpath = dirpath[:-1]

    images = glob.glob(dirpath+'/' + prefix + '*.' + image_format)

    for fname in images:
        img = cv2.imread(fname)
        gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

        # Find the chess board corners
        ret, corners = cv2.findChessboardCorners(gray, (width, height), None)

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

            corners2 = cv2.cornerSubPix(gray, corners, (11, 11), (-1, -1), criteria)
            imgpoints.append(corners2)

            # Draw and display the corners
            img = cv2.drawChessboardCorners(img, (width, height), corners2, ret)
            cv2.imshow("chessboard", img)
            cv2.waitKey(1000)

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

    return [ret, mtx, dist, rvecs, tvecs]
def save_coefficients(mtx, dist, path):
    """ Save the camera matrix and the distortion coefficients to given path/file. """
    cv_file = cv2.FileStorage(path, cv2.FILE_STORAGE_WRITE)
    cv_file.write("K", mtx)
    cv_file.write("D", dist)
    # note you *release* you don't close() a FileStorage object
    cv_file.release()


def load_coefficients(path):
    """ Loads camera matrix and distortion coefficients. """
    # FILE_STORAGE_READ
    cv_file = cv2.FileStorage(path, cv2.FILE_STORAGE_READ)

    # note we also have to specify the type to retrieve other wise we only get a
    # FileNode object back instead of a matrix
    camera_matrix = cv_file.getNode("K").mat()
    dist_matrix = cv_file.getNode("D").mat()

    cv_file.release()
    return [camera_matrix, dist_matrix]


if __name__ == '__main__':
   
    image_dir    = "/home/mohsen/Documents/Finger_Robot"
    prefix       = "imgcalib/"
    image_format = "png"
    square_size  = 0.021 # if square_size is 1.5 centimeters, it would be better to write it as 0.015 meters.
    width        = 9
    height       = 6

    save_file = "camCalibration.dat"



    ret, mtx, dist, rvecs, tvecs = calibrate(image_dir, prefix, image_format, square_size, width, height)
    save_coefficients(mtx, dist, save_file)
    print("Calibration is finished. RMS: ", ret)