예제 #1
0
    def handle_monocular(self, msg):
        if self.c == None:
            if self._camera_name:
                self.c = MonoCalibrator(
                    self._boards,
                    self._calib_flags,
                    self._pattern,
                    name=self._camera_name,
                    detection=self._detection,
                    output=self._output,
                    checkerboard_flags=self._checkerboard_flags,
                    min_good_enough=self._min_good_enough)
            else:
                self.c = MonoCalibrator(
                    self._boards,
                    self._calib_flags,
                    self._pattern,
                    detection=self._detection,
                    output=self._output,
                    checkerboard_flags=self.checkerboard_flags,
                    min_good_enough=self._min_good_enough)

        # This should just call the MonoCalibrator
        drawable = self.c.handle_msg(msg)
        self.displaywidth = drawable.scrib.shape[1]
        self.redraw_monocular(drawable)
예제 #2
0
    def __init__(self, chess_size, dim, approximate=0):
        self.board = ChessboardInfo()
        self.board.n_cols = chess_size[0]
        self.board.n_rows = chess_size[1]
        self.board.dim = dim

        image_topic = rospy.resolve_name("monocular") + "/image_rect"
        camera_topic = rospy.resolve_name("monocular") + "/camera_info"

        tosync_mono = [
            (image_topic, sensor_msgs.msg.Image),
            (camera_topic, sensor_msgs.msg.CameraInfo),
        ]

        if approximate <= 0:
            sync = message_filters.TimeSynchronizer
        else:
            sync = functools.partial(ApproximateTimeSynchronizer,
                                     slop=approximate)

        tsm = sync([
            message_filters.Subscriber(topic, type)
            for (topic, type) in tosync_mono
        ], 10)
        tsm.registerCallback(self.queue_monocular)

        left_topic = rospy.resolve_name("stereo") + "/left/image_rect"
        left_camera_topic = rospy.resolve_name("stereo") + "/left/camera_info"
        right_topic = rospy.resolve_name("stereo") + "/right/image_rect"
        right_camera_topic = rospy.resolve_name(
            "stereo") + "/right/camera_info"

        tosync_stereo = [(left_topic, sensor_msgs.msg.Image),
                         (left_camera_topic, sensor_msgs.msg.CameraInfo),
                         (right_topic, sensor_msgs.msg.Image),
                         (right_camera_topic, sensor_msgs.msg.CameraInfo)]

        tss = sync([
            message_filters.Subscriber(topic, type)
            for (topic, type) in tosync_stereo
        ], 10)
        tss.registerCallback(self.queue_stereo)

        self.br = cv_bridge.CvBridge()

        self.q_mono = Queue()
        self.q_stereo = Queue()

        mth = ConsumerThread(self.q_mono, self.handle_monocular)
        mth.setDaemon(True)
        mth.start()

        sth = ConsumerThread(self.q_stereo, self.handle_stereo)
        sth.setDaemon(True)
        sth.start()

        self.mc = MonoCalibrator([self.board])
        self.sc = StereoCalibrator([self.board])
예제 #3
0
    def test_nochecker(self):
        # Run with same images, but looking for an incorrect chessboard size (8, 7).
        # Should raise an exception because of lack of input points.
        new_board = copy.deepcopy(board)
        new_board.n_cols = 8
        new_board.n_rows = 7

        sc = StereoCalibrator([new_board])
        self.assertRaises(CalibrationException, lambda: sc.cal(self.limages, self.rimages))
        mc = MonoCalibrator([new_board])
        self.assertRaises(CalibrationException, lambda: mc.cal(self.limages))
예제 #4
0
    def test_monocular(self):
        # Run the calibrator, produce a calibration, check it
        mc = MonoCalibrator([ board ], cv2.CALIB_FIX_K3)
        max_errs = [0.1, 0.2, 0.4, 0.7]
        for i, dim in enumerate(self.sizes):
            mc.cal(self.l[dim])
            self.assert_good_mono(mc, dim, max_errs[i])

            # Make another calibration, import previous calibration as a message,
            # and assert that the new one is good.

            mc2 = MonoCalibrator([board])
            mc2.from_message(mc.as_message())
            self.assert_good_mono(mc2, dim, max_errs[i])
예제 #5
0
    def __init__(self, chess_size, dim, approximate=0):
        self.board = ChessboardInfo()
        self.board.n_cols = chess_size[0]
        self.board.n_rows = chess_size[1]
        self.board.dim = dim

        image_topic = rospy.resolve_name("monocular") + "/image_rect"
        camera_topic = rospy.resolve_name("monocular") + "/camera_info"

        tosync_mono = [
            (image_topic, sensor_msgs.msg.Image),
            (camera_topic, sensor_msgs.msg.CameraInfo),
        ]

        if approximate <= 0:
            sync = message_filters.TimeSynchronizer
        else:
            sync = functools.partial(ApproximateTimeSynchronizer, slop=approximate)

        tsm = sync([message_filters.Subscriber(topic, type) for (topic, type) in tosync_mono], 10)
        tsm.registerCallback(self.queue_monocular)

        left_topic = rospy.resolve_name("stereo") + "/left/image_rect"
        left_camera_topic = rospy.resolve_name("stereo") + "/left/camera_info"
        right_topic = rospy.resolve_name("stereo") + "/right/image_rect"
        right_camera_topic = rospy.resolve_name("stereo") + "/right/camera_info"

        tosync_stereo = [
            (left_topic, sensor_msgs.msg.Image),
            (left_camera_topic, sensor_msgs.msg.CameraInfo),
            (right_topic, sensor_msgs.msg.Image),
            (right_camera_topic, sensor_msgs.msg.CameraInfo)
        ]

        tss = sync([message_filters.Subscriber(topic, type) for (topic, type) in tosync_stereo], 10)
        tss.registerCallback(self.queue_stereo)

        self.br = cv_bridge.CvBridge()

        self.q_mono = Queue()
        self.q_stereo = Queue()

        mth = ConsumerThread(self.q_mono, self.handle_monocular)
        mth.setDaemon(True)
        mth.start()

        sth = ConsumerThread(self.q_stereo, self.handle_stereo)
        sth.setDaemon(True)
        sth.start()

        self.mc = MonoCalibrator([self.board])
        self.sc = StereoCalibrator([self.board])
예제 #6
0
    def test_monocular(self):
        # Run the calibrator, produce a calibration, check it
        for i, setup in enumerate(self.setups):
            board = ChessboardInfo()
            board.n_cols = setup.cols
            board.n_rows = setup.rows
            board.dim = self.board_width_dim

            mc = MonoCalibrator([ board ], flags=cv2.CALIB_FIX_K3, pattern=setup.pattern)

            if 0:
                # display the patterns viewed by the camera
                for pattern_warped in self.limages[i]:
                    cv2.imshow("toto", pattern_warped)
                    cv2.waitKey(0)

            mc.cal(self.limages[i])
            self.assert_good_mono(mc, self.limages[i], setup.lin_err)

            # Make sure the intrinsics are similar
            err_intrinsics = numpy.linalg.norm(mc.intrinsics - self.K, ord=numpy.inf)
            self.assert_(err_intrinsics < setup.K_err,
                         'intrinsics error is %f for resolution i = %d' % (err_intrinsics, i))
            print('intrinsics error is %f' % numpy.linalg.norm(mc.intrinsics - self.K, ord=numpy.inf))
예제 #7
0
class CameraCheckerNode:
    def __init__(self, chess_size, dim, approximate=0):
        self.board = ChessboardInfo()
        self.board.n_cols = chess_size[0]
        self.board.n_rows = chess_size[1]
        self.board.dim = dim

        image_topic = rospy.resolve_name("monocular") + "/image_rect"
        camera_topic = rospy.resolve_name("monocular") + "/camera_info"

        tosync_mono = [
            (image_topic, sensor_msgs.msg.Image),
            (camera_topic, sensor_msgs.msg.CameraInfo),
        ]

        if approximate <= 0:
            sync = message_filters.TimeSynchronizer
        else:
            sync = functools.partial(ApproximateTimeSynchronizer,
                                     slop=approximate)

        tsm = sync([
            message_filters.Subscriber(topic, type)
            for (topic, type) in tosync_mono
        ], 10)
        tsm.registerCallback(self.queue_monocular)

        left_topic = rospy.resolve_name("stereo") + "/left/image_rect"
        left_camera_topic = rospy.resolve_name("stereo") + "/left/camera_info"
        right_topic = rospy.resolve_name("stereo") + "/right/image_rect"
        right_camera_topic = rospy.resolve_name(
            "stereo") + "/right/camera_info"

        tosync_stereo = [(left_topic, sensor_msgs.msg.Image),
                         (left_camera_topic, sensor_msgs.msg.CameraInfo),
                         (right_topic, sensor_msgs.msg.Image),
                         (right_camera_topic, sensor_msgs.msg.CameraInfo)]

        tss = sync([
            message_filters.Subscriber(topic, type)
            for (topic, type) in tosync_stereo
        ], 10)
        tss.registerCallback(self.queue_stereo)

        self.br = cv_bridge.CvBridge()

        self.q_mono = Queue()
        self.q_stereo = Queue()

        mth = ConsumerThread(self.q_mono, self.handle_monocular)
        mth.setDaemon(True)
        mth.start()

        sth = ConsumerThread(self.q_stereo, self.handle_stereo)
        sth.setDaemon(True)
        sth.start()

        self.mc = MonoCalibrator([self.board])
        self.sc = StereoCalibrator([self.board])

    def queue_monocular(self, msg, cmsg):
        self.q_mono.put((msg, cmsg))

    def queue_stereo(self, lmsg, lcmsg, rmsg, rcmsg):
        self.q_stereo.put((lmsg, lcmsg, rmsg, rcmsg))

    def mkgray(self, msg):
        return self.mc.mkgray(msg)

    def image_corners(self, im):
        (ok, corners, b) = self.mc.get_corners(im)
        if ok:
            return corners
        else:
            return None

    def handle_monocular(self, msg):

        (image, camera) = msg
        gray = self.mkgray(image)
        C = self.image_corners(gray)
        if C is not None:
            linearity_rms = self.mc.linear_error(C, self.board)

            # Add in reprojection check
            image_points = C
            object_points = self.mc.mk_object_points([self.board],
                                                     use_board_size=True)[0]
            dist_coeffs = numpy.zeros((4, 1))
            camera_matrix = numpy.array(
                [[camera.P[0], camera.P[1], camera.P[2]],
                 [camera.P[4], camera.P[5], camera.P[6]],
                 [camera.P[8], camera.P[9], camera.P[10]]])
            ok, rot, trans = cv2.solvePnP(object_points, image_points,
                                          camera_matrix, dist_coeffs)
            # Convert rotation into a 3x3 Rotation Matrix
            rot3x3, _ = cv2.Rodrigues(rot)
            # Reproject model points into image
            object_points_world = numpy.asmatrix(rot3x3) * numpy.asmatrix(
                object_points.squeeze().T) + numpy.asmatrix(trans)
            reprojected_h = camera_matrix * object_points_world
            reprojected = (reprojected_h[0:2, :] / reprojected_h[2, :])
            reprojection_errors = image_points.squeeze().T - reprojected

            reprojection_rms = numpy.sqrt(
                numpy.sum(numpy.array(reprojection_errors)**2) /
                numpy.product(reprojection_errors.shape))

            # Print the results
            print(
                "Linearity RMS Error: %.3f Pixels      Reprojection RMS Error: %.3f Pixels"
                % (linearity_rms, reprojection_rms))
        else:
            print('no chessboard')

    def handle_stereo(self, msg):

        (lmsg, lcmsg, rmsg, rcmsg) = msg
        lgray = self.mkgray(lmsg)
        rgray = self.mkgray(rmsg)

        L = self.image_corners(lgray)
        R = self.image_corners(rgray)
        if L is not None and R is not None:
            epipolar = self.sc.epipolar_error(L, R)

            dimension = self.sc.chessboard_size(L,
                                                R,
                                                self.board,
                                                msg=(lcmsg, rcmsg))

            print("epipolar error: %f pixels   dimension: %f m" %
                  (epipolar, dimension))
        else:
            print("no chessboard")
예제 #8
0
def cal_from_tarfile(boards,
                     tarname,
                     mono=False,
                     upload=False,
                     calib_flags=0,
                     visualize=False,
                     alpha=1.0):
    if mono:
        calibrator = MonoCalibrator(boards, calib_flags)
    else:
        calibrator = StereoCalibrator(boards, calib_flags)

    calibrator.do_tarfile_calibration(tarname)

    print(calibrator.ost())

    if upload:
        info = calibrator.as_message()
        if mono:
            set_camera_info_service = rospy.ServiceProxy(
                "%s/set_camera_info" % rospy.remap_name("camera"),
                sensor_msgs.srv.SetCameraInfo)

            response = set_camera_info_service(info)
            if not response.success:
                raise RuntimeError(
                    "connected to set_camera_info service, but failed setting camera_info"
                )
        else:
            set_left_camera_info_service = rospy.ServiceProxy(
                "%s/set_camera_info" % rospy.remap_name("left_camera"),
                sensor_msgs.srv.SetCameraInfo)
            set_right_camera_info_service = rospy.ServiceProxy(
                "%s/set_camera_info" % rospy.remap_name("right_camera"),
                sensor_msgs.srv.SetCameraInfo)

            response1 = set_left_camera_info_service(info[0])
            response2 = set_right_camera_info_service(info[1])
            if not (response1.success and response2.success):
                raise RuntimeError(
                    "connected to set_camera_info service, but failed setting camera_info"
                )

    if visualize:

        #Show rectified images
        calibrator.set_alpha(alpha)

        archive = tarfile.open(tarname, 'r')
        if mono:
            for f in archive.getnames():
                if f.startswith('left') and (f.endswith('.pgm')
                                             or f.endswith('png')):
                    filedata = archive.extractfile(f).read()
                    file_bytes = numpy.asarray(bytearray(filedata),
                                               dtype=numpy.uint8)
                    im = cv2.imdecode(file_bytes, cv2.IMREAD_COLOR)

                    bridge = cv_bridge.CvBridge()
                    try:
                        msg = bridge.cv2_to_imgmsg(im, "bgr8")
                    except cv_bridge.CvBridgeError as e:
                        print(e)

                    #handle msg returns the recitifed image with corner detection once camera is calibrated.
                    drawable = calibrator.handle_msg(msg)
                    vis = numpy.asarray(drawable.scrib[:, :])
                    #Display. Name of window:f
                    display(f, vis)
        else:
            limages = [
                f for f in archive.getnames() if (f.startswith('left') and (
                    f.endswith('pgm') or f.endswith('png')))
            ]
            limages.sort()
            rimages = [
                f for f in archive.getnames() if (f.startswith('right') and (
                    f.endswith('pgm') or f.endswith('png')))
            ]
            rimages.sort()

            if not len(limages) == len(rimages):
                raise RuntimeError(
                    "Left, right images don't match. %d left images, %d right"
                    % (len(limages), len(rimages)))

            for i in range(len(limages)):
                l = limages[i]
                r = rimages[i]

                if l.startswith('left') and (
                        l.endswith('.pgm')
                        or l.endswith('png')) and r.startswith('right') and (
                            r.endswith('.pgm') or r.endswith('png')):
                    # LEFT IMAGE
                    filedata = archive.extractfile(l).read()
                    file_bytes = numpy.asarray(bytearray(filedata),
                                               dtype=numpy.uint8)
                    im_left = cv2.imdecode(file_bytes, cv2.IMREAD_COLOR)

                    bridge = cv_bridge.CvBridge()
                    try:
                        msg_left = bridge.cv2_to_imgmsg(im_left, "bgr8")
                    except cv_bridge.CvBridgeError as e:
                        print(e)

                    #RIGHT IMAGE
                    filedata = archive.extractfile(r).read()
                    file_bytes = numpy.asarray(bytearray(filedata),
                                               dtype=numpy.uint8)
                    im_right = cv2.imdecode(file_bytes, cv2.IMREAD_COLOR)
                    try:
                        msg_right = bridge.cv2_to_imgmsg(im_right, "bgr8")
                    except cv_bridge.CvBridgeError as e:
                        print(e)

                    drawable = calibrator.handle_msg([msg_left, msg_right])

                    h, w = numpy.asarray(drawable.lscrib[:, :]).shape[:2]
                    vis = numpy.zeros((h, w * 2, 3), numpy.uint8)
                    vis[:h, :w, :] = numpy.asarray(drawable.lscrib[:, :])
                    vis[:h, w:w * 2, :] = numpy.asarray(drawable.rscrib[:, :])

                    display(l + " " + r, vis)
def cal_from_tarfile(boards, tarname, mono = False, upload = False, calib_flags = 0, visualize = False, alpha=1.0):
    if mono:
        calibrator = MonoCalibrator(boards, calib_flags)
    else:
        calibrator = StereoCalibrator(boards, calib_flags)

    calibrator.do_tarfile_calibration(tarname)

    print(calibrator.ost())

    if upload: 
        info = calibrator.as_message()
        if mono:
            set_camera_info_service = rospy.ServiceProxy("%s/set_camera_info" % rospy.remap_name("camera"), sensor_msgs.srv.SetCameraInfo)

            response = set_camera_info_service(info)
            if not response.success:
                raise RuntimeError("connected to set_camera_info service, but failed setting camera_info")
        else:
            set_left_camera_info_service = rospy.ServiceProxy("%s/set_camera_info" % rospy.remap_name("left_camera"), sensor_msgs.srv.SetCameraInfo)
            set_right_camera_info_service = rospy.ServiceProxy("%s/set_camera_info" % rospy.remap_name("right_camera"), sensor_msgs.srv.SetCameraInfo)

            response1 = set_left_camera_info_service(info[0])
            response2 = set_right_camera_info_service(info[1])
            if not (response1.success and response2.success):
                raise RuntimeError("connected to set_camera_info service, but failed setting camera_info")

    if visualize:

        #Show rectified images
        calibrator.set_alpha(alpha)

        archive = tarfile.open(tarname, 'r')
        if mono:
            for f in archive.getnames():
                if f.startswith('left') and (f.endswith('.pgm') or f.endswith('png')):
                    filedata = archive.extractfile(f).read()
                    file_bytes = numpy.asarray(bytearray(filedata), dtype=numpy.uint8)
                    im=cv2.imdecode(file_bytes,cv2.IMREAD_COLOR)

                    bridge = cv_bridge.CvBridge()
                    try:
                        msg=bridge.cv2_to_imgmsg(im, "bgr8")
                    except cv_bridge.CvBridgeError as e:
                        print(e)

                    #handle msg returns the recitifed image with corner detection once camera is calibrated.
                    drawable=calibrator.handle_msg(msg)
                    vis=numpy.asarray( drawable.scrib[:,:])
                    #Display. Name of window:f
                    display(f, vis)
        else:
            limages = [ f for f in archive.getnames() if (f.startswith('left') and (f.endswith('pgm') or f.endswith('png'))) ]
            limages.sort()
            rimages = [ f for f in archive.getnames() if (f.startswith('right') and (f.endswith('pgm') or f.endswith('png'))) ]
            rimages.sort()

            if not len(limages) == len(rimages):
                raise RuntimeError("Left, right images don't match. %d left images, %d right" % (len(limages), len(rimages)))
            
            for i in range(len(limages)):
                l=limages[i]
                r=rimages[i]

                if l.startswith('left') and (l.endswith('.pgm') or l.endswith('png')) and r.startswith('right') and (r.endswith('.pgm') or r.endswith('png')):
                    # LEFT IMAGE
                    filedata = archive.extractfile(l).read()
                    file_bytes = numpy.asarray(bytearray(filedata), dtype=numpy.uint8)
                    im_left=cv2.imdecode(file_bytes,cv2.IMREAD_COLOR)
       
                    bridge = cv_bridge.CvBridge()
                    try:
                        msg_left=bridge.cv2_to_imgmsg(im_left, "bgr8")
                    except cv_bridge.CvBridgeError as e:
                        print(e)

                    #RIGHT IMAGE
                    filedata = archive.extractfile(r).read()
                    file_bytes = numpy.asarray(bytearray(filedata), dtype=numpy.uint8)
                    im_right=cv2.imdecode(file_bytes,cv2.IMREAD_COLOR)
                    try:
                        msg_right=bridge.cv2_to_imgmsg(im_right, "bgr8")
                    except cv_bridge.CvBridgeError as e:
                        print(e)

                    drawable=calibrator.handle_msg([ msg_left,msg_right] )

                    h, w = numpy.asarray(drawable.lscrib[:,:]).shape[:2]
                    vis = numpy.zeros((h, w*2, 3), numpy.uint8)
                    vis[:h, :w ,:] = numpy.asarray(drawable.lscrib[:,:])
                    vis[:h, w:w*2, :] = numpy.asarray(drawable.rscrib[:,:])
                    
                    display(l+" "+r,vis)    
예제 #10
0
class CameraCheckerNode:

    def __init__(self, chess_size, dim, approximate=0):
        self.board = ChessboardInfo()
        self.board.n_cols = chess_size[0]
        self.board.n_rows = chess_size[1]
        self.board.dim = dim

        image_topic = rospy.resolve_name("monocular") + "/image_rect"
        camera_topic = rospy.resolve_name("monocular") + "/camera_info"

        tosync_mono = [
            (image_topic, sensor_msgs.msg.Image),
            (camera_topic, sensor_msgs.msg.CameraInfo),
        ]

        if approximate <= 0:
            sync = message_filters.TimeSynchronizer
        else:
            sync = functools.partial(ApproximateTimeSynchronizer, slop=approximate)

        tsm = sync([message_filters.Subscriber(topic, type) for (topic, type) in tosync_mono], 10)
        tsm.registerCallback(self.queue_monocular)

        left_topic = rospy.resolve_name("stereo") + "/left/image_rect"
        left_camera_topic = rospy.resolve_name("stereo") + "/left/camera_info"
        right_topic = rospy.resolve_name("stereo") + "/right/image_rect"
        right_camera_topic = rospy.resolve_name("stereo") + "/right/camera_info"

        tosync_stereo = [
            (left_topic, sensor_msgs.msg.Image),
            (left_camera_topic, sensor_msgs.msg.CameraInfo),
            (right_topic, sensor_msgs.msg.Image),
            (right_camera_topic, sensor_msgs.msg.CameraInfo)
        ]

        tss = sync([message_filters.Subscriber(topic, type) for (topic, type) in tosync_stereo], 10)
        tss.registerCallback(self.queue_stereo)

        self.br = cv_bridge.CvBridge()

        self.q_mono = Queue()
        self.q_stereo = Queue()

        mth = ConsumerThread(self.q_mono, self.handle_monocular)
        mth.setDaemon(True)
        mth.start()

        sth = ConsumerThread(self.q_stereo, self.handle_stereo)
        sth.setDaemon(True)
        sth.start()

        self.mc = MonoCalibrator([self.board])
        self.sc = StereoCalibrator([self.board])

    def queue_monocular(self, msg, cmsg):
        self.q_mono.put((msg, cmsg))

    def queue_stereo(self, lmsg, lcmsg, rmsg, rcmsg):
        self.q_stereo.put((lmsg, lcmsg, rmsg, rcmsg))

    def mkgray(self, msg):
        return self.mc.mkgray(msg)

    def image_corners(self, im):
        (ok, corners, b) = self.mc.get_corners(im)
        if ok:
            return corners
        else:
            return None

    def handle_monocular(self, msg):

        (image, camera) = msg
        gray = self.mkgray(image)
        C = self.image_corners(gray)
        if C is not None:
            linearity_rms = self.mc.linear_error(C, self.board)

            # Add in reprojection check
            image_points = C
            object_points = self.mc.mk_object_points([self.board], use_board_size=True)[0]
            dist_coeffs = numpy.zeros((4, 1))
            camera_matrix = numpy.array( [ [ camera.P[0], camera.P[1], camera.P[2]  ],
                                           [ camera.P[4], camera.P[5], camera.P[6]  ],
                                           [ camera.P[8], camera.P[9], camera.P[10] ] ] )
            ok, rot, trans = cv2.solvePnP(object_points, image_points, camera_matrix, dist_coeffs)
            # Convert rotation into a 3x3 Rotation Matrix
            rot3x3, _ = cv2.Rodrigues(rot)
            # Reproject model points into image
            object_points_world = numpy.asmatrix(rot3x3) * numpy.asmatrix(object_points.squeeze().T) + numpy.asmatrix(trans)
            reprojected_h = camera_matrix * object_points_world
            reprojected   = (reprojected_h[0:2, :] / reprojected_h[2, :])
            reprojection_errors = image_points.squeeze().T - reprojected

            reprojection_rms = numpy.sqrt(numpy.sum(numpy.array(reprojection_errors) ** 2) / numpy.product(reprojection_errors.shape))

            # Print the results
            print("Linearity RMS Error: %.3f Pixels      Reprojection RMS Error: %.3f Pixels" % (linearity_rms, reprojection_rms))
        else:
            print('no chessboard')

    def handle_stereo(self, msg):

        (lmsg, lcmsg, rmsg, rcmsg) = msg
        lgray = self.mkgray(lmsg)
        rgray = self.mkgray(rmsg)

        L = self.image_corners(lgray)
        R = self.image_corners(rgray)
        if L is not None and R is not None:
            epipolar = self.sc.epipolar_error(L, R)

            dimension = self.sc.chessboard_size(L, R, self.board, msg=(lcmsg, rcmsg))

            print("epipolar error: %f pixels   dimension: %f m" % (epipolar, dimension))
        else:
            print("no chessboard")