Fractal Aruco implementation #27934

asmorkalov · 2025-10-23T11:48:43Z

Replaces #27601
Merge with opencv/opencv_extra#1280

Pull Request Readiness Checklist

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

I agree to contribute to the project under Apache 2 License.
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
The PR is proposed to the proper branch
There is a reference to the original bug report and related work
There is accuracy test, performance test and test data in opencv_extra repository, if applicable
Patch to opencv_extra has the same branch name.
The feature is well documented and sample code can be built with the project CMake

Liiizhen · 2025-10-27T06:17:52Z

Hi! How can I commit to the new PR? It seems I don't have the permission to push updates to this PR branch.

asmorkalov · 2025-10-28T10:50:07Z

@Liiizhen I sent invitation to you.

Liiizhen · 2025-10-28T13:37:16Z

Thanks! As you mentioned in pr 27601, we can generate a PNG file of a specific size by adjusting the parameter. Do you think it's necessary to output svg?

asmorkalov · 2025-11-05T09:29:57Z

SVG is vector format and we can ensure all sizes there. PNG may be scaled somehow during printing.

asmorkalov · 2025-11-05T09:53:46Z

modules/objdetect/src/aruco/fractal_detector.cpp

+    return (1.f-decpartY)*(1.-decpartX)*float(im_grey.at<uchar>(tl.y,tl.x))+
+            decpartX*(1-decpartY)*float(im_grey.at<uchar>(tl.y,tl.x+1))+
+            (1-decpartX)*decpartY*float(im_grey.at<uchar>(tl.y+1,tl.x))+
+            decpartX*decpartY*float(im_grey.at<uchar>(tl.y+1,tl.x+1));


Debug build indicates out-of-bound access issue in cv::Mat here:

Thread 1 "opencv_test_obj" hit Catchpoint 1 (exception thrown), 0x00007ffff3cbb35a in __cxxabiv1::__cxa_throw (obj=0x5555561d1ed0, tinfo=0x7ffff50d9400 <typeinfo for cv::Exception>, dest=0x7ffff448d30e <cv::Exception::~Exception()>) at ../../../../src/libstdc++-v3/libsupc++/eh_throw.cc:81 warning: 81 ../../../../src/libstdc++-v3/libsupc++/eh_throw.cc: No such file or directory (gdb) bt #0 0x00007ffff3cbb35a in __cxxabiv1::__cxa_throw (obj=0x5555561d1ed0, tinfo=0x7ffff50d9400 <typeinfo for cv::Exception>, dest=0x7ffff448d30e <cv::Exception::~Exception()>) at ../../../../src/libstdc++-v3/libsupc++/eh_throw.cc:81 #1 0x00007ffff448fcbb in cv::error (exc=...) at /mnt/Projects/Projects/opencv/modules/core/src/system.cpp:1275 #2 0x00007ffff448fdac in cv::error (_code=-215, _err="(unsigned)i0 < (unsigned)size.p[0]", _func=0x7ffff7d8da0a "at", _file=0x7ffff7d8d6a0 "/mnt/Projects/Projects/opencv/modules/core/include/opencv2/core/mat.inl.hpp", _line=909) at /mnt/Projects/Projects/opencv/modules/core/src/system.cpp:1287 #3 0x00007ffff7c829e1 in cv::Mat::at<unsigned char> (this=0x7fffffffcd60, i0=3840, i1=1594) at /mnt/Projects/Projects/opencv/modules/core/include/opencv2/core/mat.inl.hpp:909 #4 0x00007ffff7c986ac in cv::aruco::FractalDetector::FractalDetectorImpl::getSubpixelValue (im_grey=..., p=...) at /mnt/Projects/Projects/opencv/modules/objdetect/src/aruco/fractal_detector.cpp:788 #5 0x00007ffff7c95e68 in cv::aruco::FractalDetector::detect (this=0x7fffffffd040, img=..., markers=std::vector of length 0, capacity 0, p3d=..., p2d=...) at /mnt/Projects/Projects/opencv/modules/objdetect/src/aruco/fractal_detector.cpp:564 #6 0x0000555555640401 in opencv_test::(anonymous namespace)::CV_FractalAruco_can_detect_Test::Body (this=0x5555561b1510) at /mnt/Projects/Projects/opencv/modules/objdetect/test/test_fractal_aruco.cpp:33 #7 0x000055555563fe14 in opencv_test::(anonymous namespace)::CV_FractalAruco_can_detect_Test::TestBody (this=0x5555561b1510) at /mnt/Projects/Projects/opencv/modules/objdetect/test/test_fractal_aruco.cpp:22 #8 0x00005555556c1378 in testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void> (object=0x5555561b1510, method=&virtual testing::Test::TestBody(), location=0x5555556f1353 "the test body") at /mnt/Projects/Projects/opencv/modules/ts/src/ts_gtest.cpp:3919 #9 0x00005555556bae52 in testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void> (object=0x5555561b1510, method=&virtual testing::Test::TestBody(), location=0x5555556f1353 "the test body") at /mnt/Projects/Projects/opencv/modules/ts/src/ts_gtest.cpp:3955 #10 0x000055555569edb6 in testing::Test::Run (this=0x5555561b1510) at /mnt/Projects/Projects/opencv/modules/ts/src/ts_gtest.cpp:3993 #11 0x000055555569f8a7 in testing::TestInfo::Run (this=0x55555579aa80) at /mnt/Projects/Projects/opencv/modules/ts/src/ts_gtest.cpp:4169 #12 0x00005555556a0058 in testing::TestCase::Run (this=0x55555579ac20) at /mnt/Projects/Projects/opencv/modules/ts/src/ts_gtest.cpp:4287 #13 0x00005555556acae1 in testing::internal::UnitTestImpl::RunAllTests (this=0x5555557a4f30) at /mnt/Projects/Projects/opencv/modules/ts/src/ts_gtest.cpp:6662 #14 0x00005555556c247d in testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool> (object=0x5555557a4f30, method=(bool (testing::internal::UnitTestImpl::*)(testing::internal::UnitTestImpl * const)) 0x5555556ac818 <testing::internal::UnitTestImpl::RunAllTests()>, location=0x5555556f1c10 "auxiliary test code (environments or event listeners)") at /mnt/Projects/Projects/opencv/modules/ts/src/ts_gtest.cpp:3919 #15 0x00005555556bbeef in testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool> (object=0x5555557a4f30, method=(bool (testing::internal::UnitTestImpl::*)(testing::internal::UnitTestImpl * const)) 0x5555556ac818 <testing::internal::UnitTestImpl::RunAllTests()>, location=0x5555556f1c10 "auxiliary test code (environments or event listeners)") at /mnt/Projects/Projects/opencv/modules/ts/src/ts_gtest.cpp:3955 #16 0x00005555556ab068 in testing::UnitTest::Run (this=0x555555760320 <testing::UnitTest::GetInstance()::instance>) at /mnt/Projects/Projects/opencv/modules/ts/src/ts_gtest.cpp:6271 #17 0x00005555556422c9 in RUN_ALL_TESTS () at /mnt/Projects/Projects/opencv/modules/ts/include/opencv2/ts/ts_gtest.h:22240 #18 0x00005555556425a8 in main (argc=1, argv=0x7fffffffd748) at /mnt/Projects/Projects/opencv/modules/objdetect/test/test_main.cpp:18

@Liiizhen Could you take a look on it?

OK, I will check it out.

Liiizhen · 2025-11-05T13:52:01Z

Why the test shows that these three images can't be found?

[ RUN ] CV_FractalAruco.can_detect/0, where GetParam() = "hand.jpg"
unknown file: Failure
C++ exception with description "OpenCV(4.13.0-dev) /home/ci/opencv/modules/core/include/opencv2/core/mat.inl.hpp:912: error: (-215:Assertion failed) (unsigned)i0 < (unsigned)size.p[0] in function 'at'
" thrown in the test body.
[ FAILED ] CV_FractalAruco.can_detect/0, where GetParam() = "hand.jpg" (457 ms)
[ RUN ] CV_FractalAruco.can_detect/1, where GetParam() = "close.jpg"
unknown file: Failure
C++ exception with description "OpenCV(4.13.0-dev) /home/ci/opencv/modules/core/include/opencv2/core/mat.inl.hpp:912: error: (-215:Assertion failed) (unsigned)i0 < (unsigned)size.p[0] in function 'at'
" thrown in the test body.
[ FAILED ] CV_FractalAruco.can_detect/1, where GetParam() = "close.jpg" (447 ms)
[ RUN ] CV_FractalAruco.can_detect/2, where GetParam() = "confusion.jpg"
unknown file: Failure
C++ exception with description "OpenCV(4.13.0-dev) /home/ci/opencv/modules/core/include/opencv2/core/mat.inl.hpp:912: error: (-215:Assertion failed) (unsigned)i0 < (unsigned)size.p[0] in function 'at'
" thrown in the test body.
[ FAILED ] CV_FractalAruco.can_detect/2, where GetParam() = "confusion.jpg" (530 ms)

asmorkalov · 2025-11-05T14:00:40Z

You need to pull branch with the same name from my fork of opencv_extra. The tests pass now in debug mode on my pc:

Note: Google Test filter = CV_FractalAruco.can_detect*
[==========] Running 5 tests from 1 test case.
[----------] Global test environment set-up.
[----------] 5 tests from CV_FractalAruco
[ RUN      ] CV_FractalAruco.can_detect/0, where GetParam() = "hand.jpg"
[       OK ] CV_FractalAruco.can_detect/0 (235 ms)
[ RUN      ] CV_FractalAruco.can_detect/1, where GetParam() = "close.jpg"
[       OK ] CV_FractalAruco.can_detect/1 (227 ms)
[ RUN      ] CV_FractalAruco.can_detect/2, where GetParam() = "confusion.jpg"
[       OK ] CV_FractalAruco.can_detect/2 (399 ms)
[ RUN      ] CV_FractalAruco.can_detect/3, where GetParam() = "distortion.jpg"
[       OK ] CV_FractalAruco.can_detect/3 (190 ms)
[ RUN      ] CV_FractalAruco.can_detect/4, where GetParam() = "far.jpg"
[       OK ] CV_FractalAruco.can_detect/4 (205 ms)
[----------] 5 tests from CV_FractalAruco (1256 ms total)

[----------] Global test environment tear-down
[==========] 5 tests from 1 test case ran. (1256 ms total)
[  PASSED  ] 5 tests.

Liiizhen · 2025-11-06T08:20:12Z

How to fix this:

Run cd /home/ci/opencv_extra
File size: 10779743 bytes = 10527 KiB = 10 MiB
Patch size default limit exceeded: 1024 KiB
Error: Process completed with exit code 1.

asmorkalov · 2025-11-06T11:43:11Z

Let's handle it later. We need to stabilize API and overall behaviour.

asmorkalov · 2025-11-10T08:07:21Z

@Liiizhen Next steps here:

Rename FractalMarkerSet into FractalMarkerDictionary and make it public class like it's done for classic Arucos.
Extract predefined marker factory as getPredefinedFractalArucoDictionary like it's done in classic Arucos. Reformat pre-defined dictionaries to some documented format, but not just bytes array.
Add read/write methods to get the dictionary configuration outsize.
Put fractal Aruco dictionary to detector constructor like classic Arucos.

Liiizhen · 2025-11-10T10:40:29Z

@asmorkalov Roger that. I will do these by this week.

Liiizhen and others added 21 commits July 25, 2025 16:55

Add files via upload

f9e4102

Update objdetect.hpp

de084f7

Add files via upload

fa64b53

Update CMakeLists.txt

dc98658

Update fractal_detector.cpp

56f6bfb

Create test_fractal.cpp

b075a97

Add files via upload

ea35525

Update test_fractal.cpp

abcfb2d

Update CMakeLists.txt

56f1905

Update objdetect.hpp

50fb00c

Update fractal_detector.hpp

1b15a7a

Delete modules/objdetect/include/opencv2/objdetect/fractal_marker.hpp

e062393

Update fractal_detector.cpp

d39ad41

Delete modules/objdetect/src/aruco/fractal_marker.cpp

c85efff

syntax & comment revision

2a80ea8

fixing

f96029f

extract parameter

5e5ac90

test_fractal

6cc7863

API revision

630bd7e

declaration revision

cd0233c

Do not inherit from std::vector

48b8ffc

asmorkalov added this to the 4.13.0 milestone Oct 23, 2025

asmorkalov added feature category: objdetect labels Oct 23, 2025

asmorkalov and others added 2 commits October 24, 2025 12:28

Warnings fix for MSVC.

5a4a53e

rename fractalmarker

45d3d32

asmorkalov self-assigned this Oct 30, 2025

asmorkalov commented Nov 5, 2025

View reviewed changes

asmorkalov added the GSoC label Nov 5, 2025

build fix

6001443

Reworked regression test for Fractal Aruco

9dd29ed

asmorkalov added 3 commits November 6, 2025 17:12

Relax test condition.

2cde0c9

Relax test condition

6d1582d

More test tuning.

cc4129a

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Fractal Aruco implementation #27934

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Fractal Aruco implementation #27934

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