import cv2
import matplotlib.pyplot as plt
img = cv2.imread('test3.jpg',0)
ret,thresh1 = cv2.threshold(img,127,255,cv2.THRESH_BINARY)
ret,thresh2 = cv2.threshold(img,127,255,cv2.THRESH_BINARY_INV)
ret,thresh3 = cv2.threshold(img,127,255,cv2.THRESH_TRUNC)
ret,thresh4 = cv2.threshold(img,127,255,cv2.THRESH_TOZERO)
ret,thresh5 = cv2.threshold(img,127,255,cv2.THRESH_TOZERO_INV)
images = [img,thresh1,thresh2,thresh3,thresh4,thresh5]
for i in range(6):
    plt.subplot(2,3,i+1)
    plt.imshow(images[i],cmap='gray')
    plt.xticks([])
    plt.yticks([])
plt.suptitle('fixed threshold')
plt.show()