Load image using Tkinter in Python

Question

I must be missing something, because my code doesn't work:

i have these 2 functions in a class compaClass:

def drawImgs(self):
    canvas1.delete("all")
    canvas1.create_image(0, 0, anchor=NW, image=newImg1)

def loadImg(self):
    global newImg1
    ...
    newImg1 = ImageTk.PhotoImage(resized_image1)

This thing worked well, but I thought: why using a variable outside the class? Why not using compaClass.img variable for it? It should be always available without declaring it globally. So I replaced newImg with self.img1. Now it doesn't draw anything, no error is returned - it looks a lot like original without global newImg1.

Any suggestions on what I've missed?

def drawImgs(self):
    canvas1.delete("all")
    canvas1.create_image(0, 0, anchor=NW, image=self.img1)

def loadImg(self):
    global newImg1
    ...
    self.img1 = ImageTk.PhotoImage(resized_image1)

Answer 1

An image created with ImageTk.PhotoImage and assigned to a variable that is local to a function or method is subject to garbage collection if no reference to the image object exists.

1. Make sure that compaClass is stored in a variable as long as it's needed.
2. Initialize self.img1 in your class' constructor and update it in loadImg().

Revised code:

import tkinter as tk
from tkinter import Canvas
from PIL import Image, ImageTk
class CompaClass:
    def __init__(self, root):
        self.root = root
        self.canvas = Canvas(root, width=400, height=400)
        self.canvas.pack()
        self.img1 = None
    def draw_imgs(self):
        self.canvas.delete("all")
        if self.img1:
            self.canvas.create_image(0, 0, anchor=tk.NW, image=self.img1)
        else:
            print("No image has been loaded")
    def load_img(self, image_path):
        image = Image.open(image_path)
        resized_image = image.resize((400, 400))
        self.img1 = ImageTk.PhotoImage(resized_image)
        self.draw_imgs()
root = tk.Tk() 
app = CompaClass(root)
app.load_img('your_path_to_the_image.jpg')
root.mainloop()