threshholding example using matplotlib

import cv2 as cv
import numpy as np
from matplotlib import pyplot as plt

img = cv.imread('gradient.png', 0)
_, th1 = cv.threshold(img, 50, 255, cv.THRESH_BINARY)
_, th2 = cv.threshold(img, 200, 255, cv.THRESH_BINARY_INV)
_, th3 = cv.threshold(img, 127, 255, cv.THRESH_TRUNC)
_, th4 = cv.threshold(img, 127, 255, cv.THRESH_TOZERO)
_, th5 = cv.threshold(img, 127, 255, cv.THRESH_TOZERO_INV)

titles = ['Original Image', 'Binary', 'Binary_INV', 'Trunc', 'Tozero', 'tozero_inv']
images = [img, th1, th2, th3, th4, th5]

for i in range(6):
    plt.subplot(2, 3, i+1), plt.imshow(images[i], 'gray')
    plt.title(titles[i])
    plt.xticks([]), plt.yticks([])
# cv.imshow("Image", img)
# cv.imshow("th1", th1)
# cv.imshow("th2", th2)
# cv.imshow("th3", th3)
# cv.imshow("th4", th4)
# cv.imshow("th5", th5)
# cv.waitKey(0)
# cv.destroyAllWindows()
plt.show()