Merge pull request #25938 from vrabaud:charuco

Properly check markers when none are provided. #25938

CharucoDetectorImpl::detectBoard finds temporary markers when none are provided but those are discarded when
charucoDetectorImpl::checkBoard is called.

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/objdetect/src/aruco/charuco_detector.cpp

@@ -326,8 +326,21 @@ struct CharucoDetector::CharucoDetectorImpl {
             interpolateCornersCharucoLocalHom(_markerCorners, _markerIds, image, charucoCorners, charucoIds);
         // to return a charuco corner, its closest aruco markers should have been detected
         filterCornersWithoutMinMarkers(charucoCorners, charucoIds, _markerIds, charucoCorners, charucoIds);
-}
+    }
 
+    void detectBoardWithCheck(InputArray image, OutputArray charucoCorners, OutputArray charucoIds,
+                              InputOutputArrayOfArrays markerCorners, InputOutputArray markerIds) {
+        vector<vector<Point2f>> tmpMarkerCorners;
+        vector<int> tmpMarkerIds;
+        InputOutputArrayOfArrays _markerCorners = markerCorners.needed() ? markerCorners : tmpMarkerCorners;
+        InputOutputArray _markerIds = markerIds.needed() ? markerIds : tmpMarkerIds;
+        detectBoard(image, charucoCorners, charucoIds, _markerCorners, _markerIds);
+        if (checkBoard(_markerCorners, _markerIds, charucoCorners, charucoIds) == false) {
+            CV_LOG_DEBUG(NULL, "ChArUco board is built incorrectly");
+            charucoCorners.release();
+            charucoIds.release();
+        }
+    }
 };
 
 CharucoDetector::CharucoDetector(const CharucoBoard &board, const CharucoParameters &charucoParams,
@@ -370,12 +383,7 @@ void CharucoDetector::setRefineParameters(const RefineParameters& refineParamete
 
 void CharucoDetector::detectBoard(InputArray image, OutputArray charucoCorners, OutputArray charucoIds,
                                   InputOutputArrayOfArrays markerCorners, InputOutputArray markerIds) const {
-    charucoDetectorImpl->detectBoard(image, charucoCorners, charucoIds, markerCorners, markerIds);
-    if (charucoDetectorImpl->checkBoard(markerCorners, markerIds, charucoCorners, charucoIds) == false) {
-        CV_LOG_DEBUG(NULL, "ChArUco board is built incorrectly");
-        charucoCorners.release();
-        charucoIds.release();
-    }
+    charucoDetectorImpl->detectBoardWithCheck(image, charucoCorners, charucoIds, markerCorners, markerIds);
 }
 
 void CharucoDetector::detectDiamonds(InputArray image, OutputArrayOfArrays _diamondCorners, OutputArray _diamondIds,
@@ -480,7 +488,7 @@ void CharucoDetector::detectDiamonds(InputArray image, OutputArrayOfArrays _diam
             // interpolate the charuco corners of the diamond
             vector<Point2f> currentMarkerCorners;
             Mat aux;
-            charucoDetectorImpl->detectBoard(grey, currentMarkerCorners, aux, currentMarker, currentMarkerId);
+            charucoDetectorImpl->detectBoardWithCheck(grey, currentMarkerCorners, aux, currentMarker, currentMarkerId);
 
             // if everything is ok, save the diamond
             if(currentMarkerCorners.size() > 0ull) {

modules/objdetect/test/test_charucodetection.cpp

@@ -762,23 +762,29 @@ TEST_P(CharucoBoard, testWrongSizeDetection)
     ASSERT_FALSE(boardSize.width == boardSize.height);
     aruco::CharucoBoard board(boardSize, 1.f, 0.5f, aruco::getPredefinedDictionary(aruco::DICT_4X4_50));
 
-    vector<int> detectedCharucoIds, detectedArucoIds;
-    vector<Point2f> detectedCharucoCorners;
-    vector<vector<Point2f>> detectedArucoCorners;
     Mat boardImage;
     board.generateImage(boardSize*40, boardImage);
 
     swap(boardSize.width, boardSize.height);
     aruco::CharucoDetector detector(aruco::CharucoBoard(boardSize, 1.f, 0.5f, aruco::getPredefinedDictionary(aruco::DICT_4X4_50)));
     // try detect board with wrong size
-    detector.detectBoard(boardImage, detectedCharucoCorners, detectedCharucoIds, detectedArucoCorners, detectedArucoIds);
-
-    // aruco markers must be found
-    ASSERT_EQ(detectedArucoIds.size(), board.getIds().size());
-    ASSERT_EQ(detectedArucoCorners.size(), board.getIds().size());
-    // charuco corners should not be found in board with wrong size
-    ASSERT_TRUE(detectedCharucoCorners.empty());
-    ASSERT_TRUE(detectedCharucoIds.empty());
+    for(int i: {0, 1}) {
+        vector<int> detectedCharucoIds, detectedArucoIds;
+        vector<Point2f> detectedCharucoCorners;
+        vector<vector<Point2f>> detectedArucoCorners;
+        if (i == 0) {
+            detector.detectBoard(boardImage, detectedCharucoCorners, detectedCharucoIds, detectedArucoCorners, detectedArucoIds);
+            // aruco markers must be found
+            ASSERT_EQ(detectedArucoIds.size(), board.getIds().size());
+            ASSERT_EQ(detectedArucoCorners.size(), board.getIds().size());
+        } else {
+            detector.detectBoard(boardImage, detectedCharucoCorners, detectedCharucoIds);
+        }
+
+        // charuco corners should not be found in board with wrong size
+        ASSERT_TRUE(detectedCharucoCorners.empty());
+        ASSERT_TRUE(detectedCharucoIds.empty());
+    }
 }