python图片二值化

import os
import cv2
import numpy as np

def stdfilt(img, mask):
n = mask.sum()
n1 = n - 1
c1 = cv2.filter2D(img**2, -1, mask / n1, borderType=cv2.BORDER_REFLECT)
c2 = cv2.filter2D(img, -1, mask, borderType=cv2.BORDER_REFLECT)**2 / (n * n1)
sig = np.sqrt(np.maximum(c1 - c2, 0))

return sig

def localmean(img, mask):
lm = cv2.filter2D(
img, -1, mask / mask.sum(),
borderType=cv2.BORDER_REPLICATE)

return lm

def img_binary(img, w_size=3, w_sig=0.9, w_lm=0.9):
if len(img.shape) != 2:
img = cv2.cvtColor(img, cv2.COLOR_RGB2GRAY)
img = img / 255.0
mask = np.ones(w_size)

sig = stdfilt(img, mask)
if w_lm == 0:
w_lm = 1
lm = np.mean(img)
else:
lm = localmean(img, mask)

img = 255 * ((img > sig * w_sig) & (img > w_lm * lm))

return img

if __name__ == '__main__':
#False表示读取为灰度图...
img = cv2.imread(filepath, False)
img = img_binary(img, w_size=3, w_sig=0.9, w_lm=0.9)