Drawing Image in tkinter canvas fails

Question

I am trying to make tkinter UI that changes the image by control: loading folder/file, initiate, etc.

My code is at below and it does not load any image.

window = tk.Tk()

class window_tk():
    def __init__(self,main):
        self.canvas = tk.Canvas(main, bg='white' )
        self.init_img_route = "C:/Users/ISDL_gram/Documents/hpe/3.png"
        self.img = itk.PhotoImage(file=self.init_img_route)
        self.bg= self.canvas.create_image(0,0,anchor = tk.NW,image=self.img)
        width = self.img.width()
        height = self.img.height()
        main.geometry(str(width+100)+'x'+str(height+100))
        self.canvas.pack(fill='both',expand=1)


window_tk(window)
window.mainloop()

Since I succeeded loading img when I made my code function-based, and I referred How to update an image on a Canvas? and decided to make it using class, which does not work. What did I miss? I have no clue.

I editted the code slightly, only showing codes for images.

Any error shown in the console / terminal? If yes, post the traceback. — acw1668, May 04 '21 at 12:03
I don't get the image if I do `window_tk(window)` but I get it if I do `w = window_tk(window)` so this seems to be a problem of garbage collection. — j_4321, May 04 '21 at 14:25
@j_4321 I editted the code slightly. Since the full code is long for here I only wrote things related to image. — EJ Song, May 04 '21 at 15:00
@EJSong Do you see the image if you replace `window_tk(window)` by `w = window_tk(window)`? — j_4321, May 04 '21 at 15:06

score 3 · Accepted Answer · answered May 04 '21 at 15:12

It is because you did not use a variable to store the reference of window_tk class, so it is garbage collected. Save a reference:

window = tk.Tk()

class window_tk():
    def __init__(self,main):
        self.canvas = tk.Canvas(main, bg='white' )
        self.init_img_route = "C:/Users/ISDL_gram/Documents/hpe/3.png"
        self.img = itk.PhotoImage(file=self.init_img_route)
        self.bg= self.canvas.create_image(0,0,anchor = tk.NW,image=self.img)
        width = self.img.width()
        height = self.img.height()
        main.geometry(str(width+100)+'x'+str(height+100))
        self.canvas.pack(fill='both',expand=1)


app = window_tk(window) # save a reference
window.mainloop()

Drawing Image in tkinter canvas fails

1 Answers1