Image loading problem

[Terry Reedy]

On 5/21/2016 12:54 PM, Peter Otten wrote:
> sweating_ant at yahoo.com wrote:
>
>> I am working on an image project, and I can display my image in main(). I
> mean, I can load my image in my main(). Needless, it is awkward. I am trying
> to load my image with a function, but got an empty image window popped up,
> no image content loaded. Please take a look at code:
>>
>>
>>
>> rom Tkinter import *
>>
>> def load_img(win):
>>         img = PhotoImage(file="xxx.gif")
>>         Label(win, image=img).pack()
>>
>> win = Tk()
>> load_img(win)
>> win.mainloop()
>>
>> Somebody can help me out? Thanks!
>
> It's not your fault, there's an odd quirk in the library: you have to keep a
> reference of the PhotoImage instance around to prevent the image from being
> garbage-collected. For example
>
> from Tkinter import *
>
> def load_img(win):
>     global img
>
>     img = PhotoImage(file="xxx.gif")
>     Label(win, image=img).pack()
>
> win = Tk()
> load_img(win)
> win.mainloop()
>
> will work because img is now a global that is not deleted until the script
> ends (but don't run the function twice -- then the first image will
> disappear).

The usual procedure is to create an App class and make images attributes 
of the App instance.  Then load_img would be a method and the first line 
would be 'self.img = ...'.  One can also have a list of images, to use 
in a slide show, or a dict of images, so users can select.

-- 
Terry Jan Reedy