RiddlerCalvard.py

from __future__ import print_function
import numpy as np
import argparse
import mahotas
import cv2

ap = argparse.ArgumentParser()
ap.add_argument("-i", "--image", required=True)
args = vars(ap.parse_args())

image = cv2.imread(args["image"])
image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
blurred = cv2.GaussianBlur(image, (5, 5), 0)
cv2.imshow("Image", image)

T = mahotas.thresholding.rc(blurred)
thresh = image.copy()
thresh[thresh > T] = 255
thresh[thresh < T]  = 0
thresh = cv2.bitwise_not(thresh)
cv2.imshow("Riddler-Calvard", thresh)
cv2.waitKey(0)