opencv的颜色通道中顺序是B，G，R。

图像属性

import cv2

img = cv2.imread('jk.jpg')
print(f'shape={img.shape}')
print(f'size={img.size}')
print(f'dtype={img.dtype}')

shape：图像像素的行，列，通道

size：行数 X 列数 X 通道数

dtype：图像的数据类型

像素的BGR值

import cv2
img = cv2.imread('jk.jpg')
cv2.imshow('Before the change', img)
pt_y = 169
pt_x = 118
px = img[pt_y,pt_x]
print(type(px))
print(f'BGR={px}')
blue = img[pt_y,pt_x,0]
green = img[pt_y,pt_x,1]
red = img[pt_y,pt_x,2]
print(f'BGR={blue},{green},{red}')
for y in range(img.shape[0]-50, img.shape[0]):
    for x in range(img.shape[1]-50, img.shape[1]):
        img[y,x] = [255,255,255]
cv2.imshow("After the change", img)
cv2.waitKey(0)
cv2.destroyAllWindows()