RGB to Grayscale in Python

rgb2gray.py

## Original code from the series on image processing in python
## Read the tutorial at https://thesourcecodenotes.blogspot.com/2021/07/image-processing-in-python.html

from PIL import Image, ImageTk
import tkinter as tk
 
def rgb2gray(input_image):
    if input_image.mode != 'RGB':
        return None
    else:
        output_image = Image.new('L', (input_image.width,
                                     input_image.height))
        for x in range(input_image.width):
            for y in range(input_image.height):
                pix = input_image.getpixel((x, y))
                pix = int(int(pix[0]*0.299)+
                          int(pix[1]*0.587)+
                          int(pix[2]*0.114))
                output_image.putpixel((x,y), pix)
    
    return output_image

if __name__ == "__main__":

    root = tk.Tk()
    img = Image.open("retriver.png")

    width = img.width*2+20
    height = img.height
    root.geometry(f'{width}x{height}')
     
    output_im = rgb2gray(img)
    if output_im != None:
        output_im = ImageTk.PhotoImage(output_im)
        input_im = ImageTk.PhotoImage(img)
     
        canvas = tk.Canvas(root, width=width, height=height, bg="#ffffff")
        canvas.create_image(width/4-1, height/2-1, image=input_im, state="normal")
        canvas.create_image(20+3*img.width/2-1, img.height/2-1, image=output_im, state="normal")
        canvas.place(x=0, y=0)
        canvas.pack()
        
        root.mainloop()
    else:
        print("Input image must be in 'RGB' colour space")