simple_thresholding.py

import numpy as np
import cv2
from matplotlib import pyplot as plt
img = cv2.imread("imgs/chapter5/sudoku.png", 0); 
img = cv2.blur(img, (3, 3));


# threshold -> 127
# maxval    -> 255
# Output:
#        0-127     -> 0
#       127-255    -> 255
ret,thresh1 = cv2.threshold(img,127,255,cv2.THRESH_BINARY)

# threshold -> 127
# maxval    -> 255
# Output:
#        0-127     -> 255
#       127-255    -> 0
ret,thresh2 = cv2.threshold(img,127,255,cv2.THRESH_BINARY_INV)


# threshold -> 127
# Output:
#        0-127     -> same
#       127-255    -> 127
ret,thresh3 = cv2.threshold(img,127,255,cv2.THRESH_TRUNC)


# threshold -> 127
# Output:
#        0-127     -> 0
#       127-255    -> same
ret,thresh4 = cv2.threshold(img,127,255,cv2.THRESH_TOZERO)



# threshold -> 127
# Output:
#        0-127     -> same
#       127-255    -> 0
ret,thresh5 = cv2.threshold(img,127,255,cv2.THRESH_TOZERO_INV)



f = plt.figure(figsize=(15,25))
f.add_subplot(3, 2, 1).set_title('Original Image');
plt.imshow(img, cmap = "gray")
f.add_subplot(3, 2, 2).set_title('THRESH_BINARY');
plt.imshow(thresh1, cmap = "gray");
f.add_subplot(3, 2, 3).set_title('THRESH_BINARY_INV');
plt.imshow(thresh2, cmap = "gray");
f.add_subplot(3, 2, 4).set_title('THRESH_TRUNC');
plt.imshow(thresh3, cmap = "gray");
f.add_subplot(3, 2, 5).set_title('THRESH_TOZERO');
plt.imshow(thresh4, cmap = "gray");
f.add_subplot(3, 2, 6).set_title('THRESH_TOZERO_INV');
plt.imshow(thresh5, cmap = "gray");
plt.show();