import numpy as np
import cv2

img = cv2.imread('map.jpg')
img = cv2.bitwise_not(img)

img_gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
img_blur = cv2.medianBlur(img_gray, 9)

kernel = np.ones((5, 5), np.uint8)

img_thr = np.byte(img_blur > 127) * 255

img_opening = cv2.morphologyEx(img_thr, cv2.MORPH_OPEN, kernel)
img_closing = cv2.morphologyEx(img_opening, cv2.MORPH_CLOSE, kernel)

result = img_gray * 0.5 + img_closing * 0.5

cv2.imwrite('result.jpg', result)