Python - Bothat

import cv2 as cv

import numpy as np

import matplotlib.pyplot as plt

img1 = cv.imread('medialuna.jpg',0)

ret,img1 = cv.threshold (img1,0,255,cv.THRESH_OTSU)

kernel = cv.getStructuringElement (cv.MORPH_CROSS,(4,4))

bothat = cv.morphologyEx(img1,cv.MORPH_BLACKHAT,kernel)

plt.imshow(bothat,cmap='gray')