convert image to grayscale opencv

img = cv2.imread(path)
img_gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

img_gray_mode = cv2.imread(path, cv2.IMREAD_GRAYSCALE)

import cv2

# Reading color image as grayscale
gray = cv2.imread("color-img.png",0)

# Showing grayscale image
cv2.imshow("Grayscale Image", gray)

# waiting for key event
cv2.waitKey(0)

# destroying all windows
cv2.destroyAllWindows()