roboflow/supervision · error · ValueError

{anchor} is not supported.

Error message

{anchor} is not supported.

What it means

Raised by _oriented_box_anchors when the given Position anchor is not a key in _ANCHOR_OFFSETS. Only a subset of Position values has a defined offset for oriented boxes (the map in boxes.py lists them, e.g. CENTER, CENTER_LEFT, BOTTOM_CENTER). Other Position enum members are valid elsewhere in supervision but have no oriented-box anchor mapping.

Source

Thrown at src/supervision/detection/utils/boxes.py:387

    Examples:
        ```pycon
        >>> import numpy as np
        >>> from supervision.detection.utils.boxes import _oriented_box_anchors
        >>> from supervision.geometry.core import Position
        >>> corners = np.array(
        ...     [[[0, 0], [10, 0], [10, 4], [0, 4]]], dtype=np.float32
        ... )
        >>> _oriented_box_anchors(corners, Position.BOTTOM_CENTER)
        array([[5., 4.]])

        ```
    """
    corners = np.asarray(xyxyxyxy, dtype=np.float64)
    if corners.ndim != 3 or corners.shape[-2:] != (4, 2):
        raise ValueError(f"xyxyxyxy must have shape (N, 4, 2); got {corners.shape}")
    if anchor not in _ANCHOR_OFFSETS:
        raise ValueError(f"{anchor} is not supported.")
    sx, sy = _ANCHOR_OFFSETS[anchor]

    center = corners.mean(axis=1)
    # Two perpendicular half-side vectors per box.
    half_side_a = (corners[:, 1] - corners[:, 0]) / 2
    half_side_b = (corners[:, 2] - corners[:, 1]) / 2

    # Map each box's own sides onto the image axes: the side more aligned with
    # the x-axis plays the role of width, the other of height. This makes the
    # offsets collapse to the axis-aligned frame when the box is not rotated.
    is_width = np.abs(half_side_a[:, 0]) >= np.abs(half_side_b[:, 0])
    width = np.where(is_width[:, None], half_side_a, half_side_b)
    height = np.where(is_width[:, None], half_side_b, half_side_a)
    # Point width toward +x and height toward +y so the offset signs are stable.
    width = np.where((width[:, 0] < 0)[:, None], -width, width)
    height = np.where((height[:, 1] < 0)[:, None], -height, height)

    return cast(npt.NDArray[np.float64], center + sx * width + sy * height)

View on GitHub (pinned to 7f254d9784)

Solutions

1. Use one of the supported anchors, e.g. Position.CENTER, Position.CENTER_LEFT, or Position.BOTTOM_CENTER — check the _ANCHOR_OFFSETS keys in boxes.py for the full list.
2. If you need an unsupported anchor for OBBs, compute it yourself from corners[:, i] vertices instead of the helper.
3. Keep a project-level allowlist of anchors and validate against it when config is shared between aligned and oriented pipelines.

Example fix

# before
_oriented_box_anchors(corners, Position.TOP_RIGHT)  # ValueError: not supported

# after
_oriented_box_anchors(corners, Position.CENTER)

from supervision.detection.utils.boxes import _ANCHOR_OFFSETS

if position not in _ANCHOR_OFFSETS:
    position = sv.Position.CENTER  # or raise a config error
anchors = _oriented_box_anchors(corners, position)

def is_supported_obb_anchor(p) -> bool:
    from supervision.detection.utils.boxes import _ANCHOR_OFFSETS
    return p in _ANCHOR_OFFSETS

try:
    anchors = _oriented_box_anchors(corners, position)
except ValueError as err:
    if 'not supported' in str(err):
        anchors = _oriented_box_anchors(corners, sv.Position.CENTER)
    else:
        raise

When it happens

Trigger: Calling an annotator or _oriented_box_anchors with a Position such as Position.TOP_RIGHT or any member not present in _ANCHOR_OFFSETS, while detections carry oriented bounding boxes.

Common situations: Reusing anchor config from axis-aligned code (where all Position values are accepted) with rotated-box detections; upgrading supervision and passing a newly added Position member that has not been added to the oriented-box map yet.

Related errors

• xyxyxyxy must have shape (N, 4, 2); got {corners.shape}
• {anchor} is not supported.
• corners must have shape (N, 4, 2); got {corners.shape}
• xyxyxyxy must have shape (N, 4, 2); got {xyxyxyxy.shape}
• Triggering anchors cannot be empty.

AI-assisted analysis of roboflow/supervision@7f254d9784 (2026-08-15). Data as JSON: /api/errors/6ff73f076de64bbd. Report an issue: GitHub.