Class Instances

detectron2/structures/instances.py:7–191

This class represents a list of instances in an image. It stores the attributes of instances (e.g., boxes, masks, labels, scores) as "fields". All fields must have the same ``__len__`` which is the number of instances. All other (non-field) attributes of this class are considered p

class Instances:
    """
    This class represents a list of instances in an image.
    It stores the attributes of instances (e.g., boxes, masks, labels, scores) as "fields".
    All fields must have the same ``__len__`` which is the number of instances.

    All other (non-field) attributes of this class are considered private:
    they must start with '_' and are not modifiable by a user.

    Some basic usage:

    1. Set/get/check a field:

       .. code-block:: python

          instances.gt_boxes = Boxes(...)
          print(instances.pred_masks)  # a tensor of shape (N, H, W)
          print('gt_masks' in instances)

    2. ``len(instances)`` returns the number of instances
    3. Indexing: ``instances[indices]`` will apply the indexing on all the fields
       and returns a new :class:`Instances`.
       Typically, ``indices`` is a integer vector of indices,
       or a binary mask of length ``num_instances``

       .. code-block:: python

          category_3_detections = instances[instances.pred_classes == 3]
          confident_detections = instances[instances.scores > 0.9]
    """

    def __init__(self, image_size: Tuple[int, int], **kwargs: Any):
        """
        Args:
            image_size (height, width): the spatial size of the image.
            kwargs: fields to add to this `Instances`.
        """
        self._image_size = image_size
        self._fields: Dict[str, Any] = {}
        for k, v in kwargs.items():
            self.set(k, v)

    @property
    def image_size(self) -> Tuple[int, int]:
        """
        Returns:
            tuple: height, width
        """
        return self._image_size

    def __setattr__(self, name: str, val: Any) -> None:
        if name.startswith("_"):
            super().__setattr__(name, val)
        else:
            self.set(name, val)

    def __getattr__(self, name: str) -> Any:
        if name == "_fields" or name not in self._fields: