roboflow/supervision · error · ValueError

LabelMe rectangle shape (label={label}) has {len(points)} po

Error message

LabelMe rectangle shape (label={label}) has {len(points)} point(s); expected at least 2.

What it means

Raised when a LabelMe rectangle shape has fewer than 2 points. A rectangle is defined by two corner points ([x1, y1] and [x2, y2]) which supervision converts to an xyxy box; with 0 or 1 points the box is underdetermined, so parsing aborts before _rectangle_to_xyxy.

Source

Thrown at src/supervision/dataset/formats/labelme.py:119

            continue
        label = shape.get("label")
        points_raw = shape.get("points")
        if label is None or points_raw is None:
            missing = "label" if label is None else "points"
            raise ValueError(
                f"LabelMe shape of type {shape_type!r} is missing the "
                f"required {missing!r} field."
            )
        points = np.array(points_raw, dtype=np.float32)
        if points.ndim != 2 or points.shape[1] != 2:
            raise ValueError(
                f"LabelMe shape of type {shape_type!r} (label={label!r}) has "
                f"malformed points: expected an (N, 2) array, got shape "
                f"{points.shape}."
            )
        if shape_type == "rectangle":
            if len(points) < 2:
                raise ValueError(
                    f"LabelMe rectangle shape (label={label!r}) has "
                    f"{len(points)} point(s); expected at least 2."
                )
            xyxy = _rectangle_to_xyxy(points)
            polygon = _xyxy_to_polygon(xyxy)
        else:
            if len(points) < 3:
                raise ValueError(
                    f"LabelMe polygon shape (label={label!r}) has "
                    f"{len(points)} point(s); expected at least 3."
                )
            xyxy = polygon_to_xyxy(polygon=points).astype(np.float32)
            polygon = points
        xyxy_list.append(xyxy)
        class_ids.append(class_to_index[label])
        if with_masks:
            polygons.append(polygon)

View on GitHub (pinned to 7f254d9784)

Solutions

Find the rectangle shape with <2 points in the failing JSON and add the second corner: [[x1, y1], [x2, y2]].
If the shape is an abandoned drawing artifact, delete that shape object entirely.
Fix the annotation-writing code to only persist completed rectangles.

Example fix

// before
{"shape_type": "rectangle", "label": "dog", "points": [[10, 10]]}
// after
{"shape_type": "rectangle", "label": "dog", "points": [[10, 10], [100, 140]]}

Defensive patterns

Strategy: validation

Validate before calling

def rectangle_complete(shape: dict) -> bool:
    """A LabelMe rectangle needs at least two [x, y] points."""
    return shape.get('shape_type') != 'rectangle' or len(shape.get('points', [])) >= 2

Try / catch

try:
    dataset = sv.DetectionDataset.from_labelme(images_dir, ann_dir)
except ValueError as e:
    if 'rectangle' in str(e) and 'expected at least 2' in str(e):
        raise SystemExit(f'Complete or remove the degenerate rectangle: {e}') from e
    raise

Prevention

Discard unfinished drawings in annotation tooling (no single-click rectangles).
Validate rectangle shapes during export from custom tools.
Periodically lint annotation JSON for degenerate geometry.

When it happens

Trigger: DetectionDataset.from_labelme where a shape with "shape_type": "rectangle" has "points": [] or a single [[x, y]] entry.

Common situations: Annotations saved mid-drawing (click without drag); converter bugs writing only one corner; hand-authored JSON with an empty points array; exports from tools that emit degenerate rectangles.

Related errors

AI-assisted analysis of roboflow/supervision@7f254d9784 (2026-08-15). Data as JSON: /api/errors/f6caf70658583b33. Report an issue: GitHub.