def get_detector(cls, config, name, scale_factor=1.1, min_neighbors=3):
        key = (name, scale_factor, min_neighbors)
        if key in cls._INSTANCES:
            LOGGER.info("Reusing %s detector.", key)
            return cls._INSTANCES[key]
        cls._INSTANCES[key] = FeatureDetector(
                config, name, scale_factor, min_neighbors)
        return cls._INSTANCES[key]