import cv2 as cv
import numpy as np
from matplotlib import pyplot as plt
img = cv.imread('j_2.png', cv.IMREAD_GRAYSCALE)
assert img is not None, 'file could not be read, check with os.path.exists()'
kernel = np.ones((5, 5), np.uint8)
opening = cv.morphologyEx(img, cv.MORPH_OPEN, kernel)
plt.subplot(121), plt.imshow(img), plt.title('Original')
plt.xticks([]), plt.yticks([])
plt.subplot(122), plt.imshow(opening), plt.title('Opening')
plt.xticks([]), plt.yticks([])
plt.show()
