import cv2
import torch
import numpy as np


class CannyDetector:
    def __call__(self, img, low_threshold=100, high_threshold=200):
        """
        input: array or tensor (H,W,3)
        output: array (H,W)
        """
        if torch.is_tensor(img):
            img = img.cpu().detach().numpy().astype(np.uint8)
        return cv2.Canny(img, low_threshold, high_threshold)