convert color image to grayscale python code example

Example 1: how to convert into grayscale opencv

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()

Example 2: cvtcolor rgb to gray

cv::Mat img
cv::cvtColor(img, img, CV_BGR2GRAY);