Got blurred image on resizing image as label in tkinter window in python

Question

I try to put a image label on tkinter window, I add the functionality of grow and shrink the image and move the image on the main tkinter window

But as I click grow button, it increases size but got blurred and vice versa for shrink button

Here is my code, tell me where i am wrong?

from tkinter import* 
from PIL import Image,ImageTk 
from tkinter import Tk, Label, Button
from tkinter.filedialog import askopenfilename 
import tkinter as tk 

root = Tk() 

root.title("image edit")
root.geometry('1000x600+500+100')
root.resizable(False,False)

#take image file from the system 
Tk().withdraw()
filepath = askopenfilename()
img = Image.open(filepath)
tk_im = ImageTk.PhotoImage(img)

xi=100
yi=100
wi=100
hi=100
#function to increase size of label 
def grow():
             
    global img
    global my_label
    global xi
    global yi
    global wi 
    global hi 
    i=0
    while i<2:
      img = img.resize((xi, yi))
      tk_im=ImageTk.PhotoImage(img)
  
      my_label.configure(width=wi, 
      height=hi,image=tk_im)
    
      my_label.image=tk_im
      xi+=1
      yi+=1
      i+=1 
      wi+=1
      hi+=1

#function to decrease size of image 
def shrink():
    global my_label
    global img
    global xi
    global yi
    global wi 
    global hi 
    i=0
    while i<2:
      img = img.resize((xi, yi))
      tk_im=ImageTk.PhotoImage(img)
      my_label.configure(width=wi,
      height=hi,image=tk_im)
    
      my_label.image=tk_im
      xi-=1
      yi-=1
      i+=1 
      wi-=1
      hi-=1

set image in label

my_label=Label(root,image=tk_im)  
my_label.image=tk_im

my_label.pack()

buttons to resize image

grow_button=Button(root,text=
"grow",command=grow)

grow_button.pack()

shrink_button=Button(root,text=
"shrink",command=shrink)

shrink_button.pack()

root.mainloop() 

Answer 1

your code is not exactly 'wrong' as people have different levels of quality they expect. if you want to be able to set your quality yourself however i would suggest resizing with Nearest Neighbour resampling so you don't introduce any new, blurred colours - just ones already existing in your image:

import numpy as np
from PIL import Image

im = Image.open("ImageTK").convert('RGB')
im = im.resize((200,200),resample=Image.NEAREST)
im.save("result.png")

You can go from a Pillow image to a numpy array with:

numpy_array = np.array(pillowImage)

and from numpy array to a Pillow image with:

pillow_image = Image.fromarray(numpyArray)

You could also use PIL.Image/openCV and PIL.ImageFilter modules:

from PIL import Image, ImageFilter
import cv2

image = cv2.resize(image, fx=0.5, fy=0.5, interpolation=cv2.INTER_AREA)
image = Image.fromarray(image)

Here, fx and fy are the values you have to set yourself.

Answer 2

You should not modify the original image because its quality may be changed especially after shrinking. Save the resized image into another image as below:

      resized_img = img.resize((xi, yi))  # don't modify the original image
      tk_im = ImageTk.PhotoImage(resized_img)