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calib document fix - #30208 Documentation changes - three doxygen blocks in `modules/objdetect`. - **`findChessboardCorners`** (PR#22083): whether the returned order pins down a unique physical corner depends on the **parity** of the two `patternSize` dimensions, not on whether they differ. Quads are built from the dark squares only (`calibinit.cpp:755` `THRESH_BINARY`, `:796` white frame, `:1919` holes-only), so a rotation is admissible only if it maps dark squares onto dark squares. For `patternSize` of w x h interior corners the squares form a (w+1) x (h+1) grid, so 180° preserves the colouring exactly when w and h share parity: | `patternSize` | distinct origins | ambiguity | |--------------------------------|------------------|---------------| | different parity (9x6, 8x5) | 1 | none | | same parity, w != h (8x6, 7x5) | 2 | 180° | | w == h (7x7, 8x8) | 4 | 90° | The square case is not colour: the transpose at `calibinit.cpp:1745` is a no-op when `width == pattern_size.width`, so the detector cannot tell rows from columns. Verified over 24 in-plane rotations and 60 perspective views per board, zero detection failures; inverting the square colouring moves the origin but not the count. Practical consequence is the reverse of what was documented: the common 9x6 board is unambiguous, while this docstring's own sample `Size patternsize(8,6)` is not. The note now recommends a board whose dimensions differ in parity first, then #findChessboardCornersSB + `CALIB_CB_MARKER`, then ChArUco. Still harmless for intrinsics (each view absorbs the rotation into its own pose); still breaks hand-eye. - **`findCirclesGrid`** (PR#7312): the returned points are the keypoint locations reported by `blobDetector` as-is, without refinement - the parameter is a `FeatureDetector` and `SimpleBlobDetector` is only the default, so the points are not necessarily moment centroids. Under perspective the apparent centre of a projected circle can be displaced from the projection of the physical centre; the displacement vanishes when the board is parallel to the image plane and is not removed by fitting an ellipse. Points at the `blobDetector = NULL` path for supplying corrected centres. Describes the bias qualitatively rather than quoting a fixed estimate. - **`setLegacyPattern` / `detectBoard`** (PR#23152, PR#29636): the flag is a no-op on odd-row boards, and a wrong setting fails silently - markers detected, zero corners, only a `CV_LOG_DEBUG` line; notes that calib.io boards use the legacy layout and aligns the 4.6.0 version wording across both headers. ### 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 - [ ] 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. - [x] The feature is well documented and sample code can be built with the project CMake