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Merge pull request #3024 from andy-held:charuco-selectAndRefineChessboardCorners

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aruco: fix subpixel coordinates in interpolateCornersCharuco

* adjust sub-pixel coordinates before cornerSubPix

* add test for ChArUco board subpixel accuracy
This commit is contained in:
Andreas Franek
2021-09-17 14:08:06 +02:00
committed by GitHub
parent 33b500b225
commit a1fe9c871f
2 changed files with 58 additions and 2 deletions
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4
modules/aruco/src/charuco.cpp
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@@ -315,7 +315,7 @@ static int _selectAndRefineChessboardCorners(InputArray _allCorners, InputArray
for (int i = begin; i < end; i++) {
vector<Point2f> in;
in.push_back(filteredChessboardImgPoints[i]);
in.push_back(filteredChessboardImgPoints[i] - Point2f(0.5, 0.5)); // adjust sub-pixel coordinates for cornerSubPix
Size winSize = filteredWinSizes[i];
if (winSize.height == -1 || winSize.width == -1)
winSize = Size(params->cornerRefinementWinSize, params->cornerRefinementWinSize);
@@ -325,7 +325,7 @@ static int _selectAndRefineChessboardCorners(InputArray _allCorners, InputArray
params->cornerRefinementMaxIterations,
params->cornerRefinementMinAccuracy));
filteredChessboardImgPoints[i] = in[0];
filteredChessboardImgPoints[i] = in[0] + Point2f(0.5, 0.5);
}
});

56
modules/aruco/test/test_charucodetection.cpp
View File

@@ -677,4 +677,60 @@ TEST(Charuco, testCharucoCornersCollinear_false)
EXPECT_FALSE(result);
}
// test that ChArUco board detection is subpixel accurate
TEST(Charuco, testBoardSubpixelCoords)
{
cv::Size res{500, 500};
cv::Mat K = (cv::Mat_<double>(3,3) <<
0.5*res.width, 0, 0.5*res.width,
0, 0.5*res.height, 0.5*res.height,
0, 0, 1);
// load board image with corners at round values
cv::String testImagePath = cvtest::TS::ptr()->get_data_path() + "aruco/" + "trivial_board_detection.png";
Mat img = imread(testImagePath);
cv::Mat expected_corners = (cv::Mat_<float>(9,2) <<
200, 300,
250, 300,
300, 300,
200, 250,
250, 250,
300, 250,
200, 200,
250, 200,
300, 200
);
cv::Mat gray;
cv::cvtColor(img, gray, cv::COLOR_BGR2GRAY);
auto dict = cv::aruco::getPredefinedDictionary(cv::aruco::DICT_APRILTAG_36h11);
auto board = cv::aruco::CharucoBoard::create(4, 4, 1.f, .8f, dict);
auto params = cv::aruco::DetectorParameters::create();
params->cornerRefinementMethod = cv::aruco::CORNER_REFINE_APRILTAG;
std::vector<int> ids;
std::vector<std::vector<cv::Point2f>> corners, rejected;
cv::aruco::detectMarkers(gray, dict, corners, ids, params, rejected, K);
ASSERT_EQ(ids.size(), size_t(8));
cv::Mat c_ids, c_corners;
cv::aruco::interpolateCornersCharuco(corners, ids, gray, board, c_corners, c_ids, K);
cv::Mat corners_reshaped = c_corners.reshape(1);
ASSERT_EQ(c_corners.rows, expected_corners.rows);
EXPECT_NEAR(0, cvtest::norm(expected_corners, c_corners.reshape(1), NORM_INF), 1e-3);
c_ids = cv::Mat();
c_corners = cv::Mat();
cv::aruco::interpolateCornersCharuco(corners, ids, gray, board, c_corners, c_ids);
corners_reshaped = c_corners.reshape(1);
ASSERT_EQ(c_corners.rows, expected_corners.rows);
EXPECT_NEAR(0, cvtest::norm(expected_corners, c_corners.reshape(1), NORM_INF), 1e-3);
}
}} // namespace