Thresholding (Binary, Adaptive, Otsu)

import cv2

gray = cv2.imread("doc.jpg", cv2.IMREAD_GRAYSCALE)
_, binary = cv2.threshold(gray, 127, 255, cv2.THRESH_BINARY)
_, inv    = cv2.threshold(gray, 127, 255, cv2.THRESH_BINARY_INV)
_, trunc  = cv2.threshold(gray, 127, 255, cv2.THRESH_TRUNC)

import cv2

gray = cv2.imread("page.jpg", cv2.IMREAD_GRAYSCALE)

adapt = cv2.adaptiveThreshold(
    gray, 255,
    cv2.ADAPTIVE_THRESH_GAUSSIAN_C,
    cv2.THRESH_BINARY,
    blockSize=21, C=10)

import cv2

gray = cv2.imread("coin.jpg", cv2.IMREAD_GRAYSCALE)
blur = cv2.GaussianBlur(gray, (5,5), 0)   # Otsu-র আগে noise কমান

t, otsu = cv2.threshold(blur, 0, 255,
                        cv2.THRESH_BINARY + cv2.THRESH_OTSU)
print("Chosen threshold:", t)