ret, dst = cv2.threshold(src, thresh, maxval, type)
src：输入图，只能输入单通道图像，通常来说为灰度图
dst：输出图
thresh：阈值
maxval：当像素值超过了阈值（或者小于阈值，根据type来决定），所赋予的值
type：二值化操作的类型，就是怎么处理阈值，包含以下5种类型：cv2.THRESH_BINARY；cv2.THRESH_BINARY_INV；cv2.THRESH_TRUNC；cv2.THRESH_TOZERO；cv2.THRESH_TOZERO_INV；
cv2.THRESH_BINARY 超过阈值部分取maxval（最大值），否则取0
cv2.THRESH_BINARY_INV THRESH_BINARY的反转
cv2.THRESH_TRUNC 大于阈值部分设为阈值，否则不变
cv2.THRESH_TOZERO 大于阈值部分不改变，否则设为0
cv2.THRESH_TOZERO_INV THRESH_TOZERO的反转
import cv2
import matplotlib.pyplot as plt
img = cv2.imread('cat.jpg')
img_gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
cv2.imshow('img_gray)', img_gray)
ret1, thresh1 = cv2.threshold(img_gray, 127, 255, cv2.THRESH_BINARY)
ret2, thresh2 = cv2.threshold(img_gray, 127, 255, cv2.THRESH_BINARY_INV)
ret3, thresh3 = cv2.threshold(img_gray, 127, 255, cv2.THRESH_TRUNC)
ret4, thresh4 = cv2.threshold(img_gray, 127, 255, cv2.THRESH_TOZERO)
ret5, thresh5 = cv2.threshold(img_gray, 127, 255, cv2.THRESH_TOZERO_INV)
标签：gray,img,阈值,cv2,用法说明,THRESH,threshold From： https://www.cnblogs.com/zhml/p/17658866.html