I'm trying to add images to a tkinter window, and I keep getting the error:

```
_tkinter.TclError: couldn't recognize data in image file 'Sun.png'

```

I have tried many different ways of adding images to tkinter windows, mostly as question answers from this site and they all give the same error, the code I'm currently using is the simplest version I could find and is as follows:

```
from tkinter import *

root = Tk()

photo = PhotoImage(file='Sun.png')
label = Label(root, image=photo)
label.pack()

root.mainloop()

```

Im using a mac and running the code in IDLE using python3, after trying for a few hours I've run out of ideas for how this can be fixed so sorry if it's obvious.