fix refineDetectedMarkers, add test

modules/objdetect/misc/python/test/test_objdetect_aruco.py

@@ -186,6 +186,39 @@ class aruco_objdetect_test(NewOpenCVTests):
         self.assertEqual((1, 4, 2), refine_corners[0].shape)
         np.testing.assert_array_equal(corners, refine_corners)
 
+    def test_charuco_refine(self):
+        aruco_dict = cv.aruco.getPredefinedDictionary(cv.aruco.DICT_6X6_50)
+        board_size = (3, 4)
+        board = cv.aruco.CharucoBoard(board_size, 1., .7, aruco_dict)
+        aruco_detector = cv.aruco.ArucoDetector(aruco_dict)
+        charuco_detector = cv.aruco.CharucoDetector(board)
+        cell_size = 100
+        image = board.generateImage((cell_size*board_size[0], cell_size*board_size[1]))
+        camera = np.array([[1, 0, 0.5],
+                           [0, 1, 0.5],
+                           [0, 0, 1]])
+        dist = np.array([0, 0, 0, 0, 0], dtype=np.float32).reshape(1, -1)
+
+        # generate gold corners of the ArUco markers for the test
+        gold_corners = np.array(board.getObjPoints())[:, :, 0:2]*cell_size
+
+        # detect corners
+        markerCorners, markerIds, _ = aruco_detector.detectMarkers(image)
+
+        # test refine
+        rejected = [markerCorners[-1]]
+        markerCorners, markerIds = markerCorners[:-1], markerIds[:-1]
+        markerCorners, markerIds, _, _ = aruco_detector.refineDetectedMarkers(image, board, markerCorners, markerIds,
+                                                                              rejected, cameraMatrix=camera, distCoeffs=dist)
+
+        charucoCorners, charucoIds, _, _ = charuco_detector.detectBoard(image, markerCorners=markerCorners,
+                                                                        markerIds=markerIds)
+        self.assertEqual(len(charucoIds), 6)
+        self.assertEqual(len(markerIds), 6)
+
+        for i, id in enumerate(markerIds.reshape(-1)):
+            np.testing.assert_allclose(gold_corners[id], markerCorners[i].reshape(4, 2), 0.01, 1.)
+
     def test_write_read_dictionary(self):
         try:
             aruco_dict = cv.aruco.getPredefinedDictionary(cv.aruco.DICT_5X5_50)

modules/objdetect/src/aruco/aruco_detector.cpp

@@ -1000,7 +1000,13 @@ static inline void _projectUndetectedMarkers(const Board &board, InputOutputArra
                                              OutputArray undetectedMarkersIds) {
     Mat rvec, tvec; // first estimate board pose with the current avaible markers
     Mat objPoints, imgPoints; // object and image points for the solvePnP function
-    board.matchImagePoints(detectedCorners, detectedIds, objPoints, imgPoints);
+    // To refine corners of ArUco markers the function refineDetectedMarkers() find an aruco markers pose from 3D-2D point correspondences.
+    // To find 3D-2D point correspondences uses matchImagePoints().
+    // The method matchImagePoints() works with ArUco corners (in Board/GridBoard cases) or with ChArUco corners (in CharucoBoard case).
+    // To refine corners of ArUco markers we need work with ArUco corners only in all boards.
+    // To call matchImagePoints() with ArUco corners for all boards we need to call matchImagePoints() from base class Board.
+    // The method matchImagePoints() implemented in Pimpl and we need to create temp Board object to call the base method.
+    Board(board.getObjPoints(), board.getDictionary(), board.getIds()).matchImagePoints(detectedCorners, detectedIds, objPoints, imgPoints);
     if (objPoints.total() < 4ull) // at least one marker from board so rvec and tvec are valid
         return;
     solvePnP(objPoints, imgPoints, cameraMatrix, distCoeffs, rvec, tvec);