camera calibration in opencv

toCalibrate.py

def toCalibrate(img,nx,ny):
    objpoints = []
    imgpoints = []
    objp = np.zeros((nx*ny, 3), np.float32)
    objp[:,:2] = np.mgrid[0:nx,0:ny].T.reshape(-1,2) # x,y coordinates
    
    # Find chessboard corners
    ret, corners= cv2.findChessboardCorners(img, (nx,ny), None)

    # If found, draw corners
    if ret == True:
        # Draw and display the corners
        cv2.drawChessboardCorners(img, (nx, ny), corners, ret)
        imgpoints.append(corners)
        objpoints.append(objp)
        plt.suptitle('Before Distortion', fontsize=14, fontweight='bold')
        plt.imshow(img)
        plt.show()

        global mtx
        global dist
        global rvecs
        global tvecs
        global undist
        ret, mtx, dist, rvecs, tvecs = cv2.calibrateCamera(objpoints, imgpoints, toGray(img).shape[::-1], None, None)
        undist = cv2.undistort(img, mtx, dist, None, mtx)
        
        plt.suptitle('After Distortion', fontsize=14, fontweight='bold')
        plt.imshow(undist)
        plt.show()
    if ret == False:
        print('Did not find any corners')