Class DefaultPredictor

detectron2/engine/defaults.py:160–224

Create a simple end-to-end predictor with the given config that runs on single device for a single input image. Compared to using the model directly, this class does the following additions: 1. Load checkpoint from `cfg.MODEL.WEIGHTS`. 2. Always take BGR image as the input and

class DefaultPredictor:
    """
    Create a simple end-to-end predictor with the given config that runs on
    single device for a single input image.

    Compared to using the model directly, this class does the following additions:

    1. Load checkpoint from `cfg.MODEL.WEIGHTS`.
    2. Always take BGR image as the input and apply conversion defined by `cfg.INPUT.FORMAT`.
    3. Apply resizing defined by `cfg.INPUT.{MIN,MAX}_SIZE_TEST`.
    4. Take one input image and produce a single output, instead of a batch.

    If you'd like to do anything more fancy, please refer to its source code
    as examples to build and use the model manually.

    Attributes:
        metadata (Metadata): the metadata of the underlying dataset, obtained from
            cfg.DATASETS.TEST.

    Examples:
    ::
        pred = DefaultPredictor(cfg)
        inputs = cv2.imread("input.jpg")
        outputs = pred(inputs)
    """

    def __init__(self, cfg):
        self.cfg = cfg.clone()  # cfg can be modified by model
        self.model = build_model(self.cfg)
        self.model.eval()
        if len(cfg.DATASETS.TEST):
            self.metadata = MetadataCatalog.get(cfg.DATASETS.TEST[0])

        checkpointer = DetectionCheckpointer(self.model)
        checkpointer.load(cfg.MODEL.WEIGHTS)

        self.aug = T.ResizeShortestEdge(
            [cfg.INPUT.MIN_SIZE_TEST, cfg.INPUT.MIN_SIZE_TEST], cfg.INPUT.MAX_SIZE_TEST
        )

        self.input_format = cfg.INPUT.FORMAT
        assert self.input_format in ["RGB", "BGR"], self.input_format

    def __call__(self, original_image):
        """
        Args:
            original_image (np.ndarray): an image of shape (H, W, C) (in BGR order).

        Returns:
            predictions (dict):
                the output of the model for one image only.
                See :doc:`/tutorials/models` for details about the format.
        """
        with torch.no_grad():  # https://github.com/sphinx-doc/sphinx/issues/4258
            # Apply pre-processing to image.
            if self.input_format == "RGB":
                # whether the model expects BGR inputs or RGB
                original_image = original_image[:, :, ::-1]