How to Convert RGB Images to Grayscale in Python Using Pillow and Matplotlib?

Converting RGB Images to Grayscale in Python

In image processing, converting RGB images to grayscale is a common operation. While numerous approaches exist, finding the built-in method in the powerful libraries like NumPy or Matplotlib can simplify your task.

Pillow Library:

A straightforward solution is to use the Python Image Library (Pillow). It offers a convenient method to convert RGB images to grayscale:

from PIL import Image
img = Image.open('image.png').convert('L')
img.save('greyscale.png')

This code reads the RGB image, converts it to grayscale, and saves the resulting image.

Using Matplotlib with a Formula:

Another approach is to use the formula Y' = 0.2989 R 0.5870 G 0.1140 B to convert RGB images to grayscale. With Matplotlib, you can implement this as:

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.image as mpimg

def rgb2gray(rgb):
    return np.dot(rgb[...,:3], [0.2989, 0.5870, 0.1140])

img = mpimg.imread('image.png')     
gray = rgb2gray(img)    
plt.imshow(gray, cmap=plt.get_cmap('gray'), vmin=0, vmax=1)
plt.show()

This code loads the image, converts it to grayscale using the formula, and displays the grayscale image.

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