版本:opencv-python 4.5.2.52
import cv2
filename = r'b2.jpg'
b = cv2.imread(filename, flags=cv2.IMREAD_UNCHANGED)
# 显示原始图像
win_name_UNCHANGED = 'UNCHANGED'
cv2. namedWindow(win_name_UNCHANGED)
cv2.imshow(win_name_UNCHANGED, b)
# 显示灰度图
b = cv2.imread(filename, flags=cv2.IMREAD_GRAYSCALE)
win_name_GRAYSCALE = 'GRAYSCALE'
cv2. namedWindow(win_name_GRAYSCALE)
cv2.imshow(win_name_GRAYSCALE, b)
pushedKey = cv2.waitKey()
# 保存
cv2.imwrite("b_save.bmp", b)