furas.pl
# prywatne notatki - Python, Linux, Machine Learning, etc.

Sometimes image can disappear when you move code into function. It is common problem with bug in PhotoImage with garbage collector which removes image from memory when image is assigned to local variable (variable created in function). You have to assign image to global variable or to some object - ie. to Label which displays this image.

Example which uses global

import tkinter as tk  # PEP8: `import *` is not preferred

def main(root):
    global img  # <-- solution for bug 

    img = tk.PhotoImage(file="image.png")
    label = tk.Label(image=img)
    label.pack()

if __name__ == "__main__":
    root = tk.Tk()
    main(root)
    root.mainloop()

Example which uses Label object

import tkinter as tk  # PEP8: `import *` is not preferred

def main(root):
    img = tk.PhotoImage(file="image.png")
    label = tk.Label(image=img)
    label.pack()

    label.img = img  # <-- solution for bug 

if __name__ == "__main__":
    root = tk.Tk()
    main(root)
    root.mainloop()

Not so long time ago you could find this information in popular documentation for tkinter on effbot.org but now this documentation disappeared.

I found old effbot.org in Wayback Machine from 2020.11.12: PhotoImage

To display image in web browser without saving image on disk you can use BytesIO to create file-like object in memory RAM which can be used like normal file to work with it without saving on disk.

This example uses matplotlib to create PNG in memory

import io
import matplotlib …

Można użyć BytesIO do stworzenia obiektu podobnego do pliku (file-like object) ale trzymanego w pamięci RAM, który może być użyty do działań na pliku obrazka bez zapisywania na dysku.

Ten przykład używa matplotlib do stworzenia PNG w pamięci

import io
import matplotlib.pyplot as plt
import random

def generate_image():

    # genereate …