Python OpenCV: Converting an image to grayscale image

 Introduction

In this tutorial, we will discuss how the color image is converted to grayscale image using two OpenCV functions: imread() and cvtColor().

Method 1: Using imread() function

imread() function is used to read an image from the disk but while loading the image, it can be directly converted to grayscale image. The imread function is already discussed in Python OpenCV: Read/Display/Write Image

Python Code

# import the library

import cv2 as cv

# Load the image as grayscale

img = cv.imread("lena.jpg", cv.IMREAD_GRAYSCALE)

# Display the image

cv.imshow("Grayscale", img)

cv.waitKey(0)

Output

Method 1: Using cvtColor() function

cvtColor() is one the functions used to convert color channels from one to other format to other. It is also used to convert the image to grayscale.

Python Code

# import the library

import cv2 as cv

# Load the image as grayscale

img = cv.imread("lena.jpg")

# Convert to grayscale

gray = cv.cvtColor(img, cv.COLOR_BGR2GRAY)

# Display the image

cv.imshow("Original Lena", img)

# Display the grayscale image

cv.imshow("Grayscale", gray)

cv.waitKey(0)

Output