# Third-party notices

The implementation in this repository is written in MoonBit. It does not bundle upstream C or C++ implementation code and does not link to an upstream foreign-function library. The following compatibility data and bit layouts are maintained so that the public dictionaries interoperate with established fiducial-marker ecosystems.

## OpenCV ArUco compatibility data

The ArUco predefined dictionary data and rotation conventions are maintained for compatibility with OpenCV's predefined dictionaries, including `DICT_4X4_50` and the larger ArUco families.

- Reference source: [OpenCV `aruco_dictionary.cpp`](https://github.com/opencv/opencv/blob/4.x/modules/objdetect/src/aruco/aruco_dictionary.cpp)
- API and dictionary definitions: [OpenCV `aruco_dictionary.hpp`](https://github.com/opencv/opencv/blob/4.x/modules/objdetect/include/opencv2/objdetect/aruco_dictionary.hpp)
- Upstream license: [OpenCV license](https://github.com/opencv/opencv/blob/4.x/LICENSE)

OpenCV is distributed under the Apache License 2.0. This repository's own implementation remains covered by the root [Apache License 2.0](LICENSE); the references above identify the upstream compatibility source.

## AprilTag compatibility data

The AprilTag family tables and the AprilTag bit-layout conventions are maintained for interoperability with the AprilRobotics reference implementation, including `tag16h5`, `tag25h9`, `tag36h11`, and the other exposed families.

- Reference family source: [AprilRobotics `tag16h5.c`](https://github.com/AprilRobotics/apriltag/blob/master/tag16h5.c)
- Reference project: [AprilRobotics/apriltag](https://github.com/AprilRobotics/apriltag)
- Upstream license: [AprilRobotics license](https://github.com/AprilRobotics/apriltag/blob/master/LICENSE.md)

The AprilRobotics reference source uses the following BSD-2-Clause notice for the family data and implementation:

> Copyright (C) 2013-2016, The Regents of The University of Michigan.
>
> All rights reserved.
>
> Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
>
> 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
> 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

> THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

> The views and conclusions contained in the software and documentation are those of the authors and should not be interpreted as representing official policies, either expressed or implied, of the Regents of The University of Michigan.

The BSD disclaimer and the complete upstream terms are available in the linked [AprilRobotics license](https://github.com/AprilRobotics/apriltag/blob/master/LICENSE.md). The MoonBit detector and supporting algorithms in this repository are original implementation code.