JacobLinCool/captcha-recognizer

1import cv22import numpy as np3 4 5def preprocess(image: np.ndarray) -> np.ndarray:6    # Upscale, interpolation with nearest neighbor7    image = cv2.resize(image, (0, 0), fx=3, fy=3, interpolation=cv2.INTER_NEAREST)8 9    # Denoise gray-like pixels10    hsv = cv2.cvtColor(image, cv2.COLOR_BGR2HSV)11    mask = cv2.inRange(hsv, (0, 70, 70), (255, 255, 255))12    mask = cv2.bitwise_not(mask)13    image[np.where(mask)] = 25514 15    # Convert to binary16    image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)17    _, image = cv2.threshold(image, 0, 255, cv2.THRESH_OTSU)18 19    # Fix some holes20    kernel = np.ones((3, 3), np.uint8)21    image = cv2.morphologyEx(image, cv2.MORPH_OPEN, kernel, iterations=2)22 23    # add padding24    image = cv2.copyMakeBorder(25        image, 5, 5, 5, 5, cv2.BORDER_CONSTANT, value=(255, 255, 255)26    )27 28    return image29