如何使用openCV python去除文本文档中的水印？

import cv2
import numpy as np

image = cv2.imread('document_with_watermark.png')

gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

ret, threshold = cv2.threshold(gray, 200, 255, cv2.THRESH_BINARY_INV)

kernel = np.ones((3, 3), np.uint8)
opening = cv2.morphologyEx(threshold, cv2.MORPH_OPEN, kernel, iterations=1)

contours, hierarchy = cv2.findContours(opening, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

mask = np.zeros(image.shape[:2], dtype=np.uint8)
cv2.drawContours(mask, contours, -1, (255), thickness=cv2.FILLED)

result = cv2.inpaint(image, mask, 3, cv2.INPAINT_TELEA)

cv2.imshow('Result', result)
cv2.waitKey(0)
cv2.destroyAllWindows()