Python 3 tkinter |未显示URL中的图像

Question

首先，我的代码基于this StackOverflow answer。你知道吗

由于环境的原因，我试图将大部分代码打包到我调用的函数中ImgFromUrl()

import io
import tkinter as tk
import urllib.request
from PIL import Image, ImageTk

def ImgFromUrl(root, url):
    with urllib.request.urlopen(url) as connection:
        raw_data = connection.read()
    im = Image.open(io.BytesIO(raw_data))
    image = ImageTk.PhotoImage(im)
    return tk.Label(root, image=image)

root = tk.Tk()
url = "http://imgs.xkcd.com/comics/python.png"

widget = ImgFromUrl(root,url)
widget.grid(row=0,column=0)

root.mainloop()

由于某些原因，图像不会显示（尽管Tkinter窗口被自动调整为图像的大小）。你知道吗

但是这是可行的：

# same imports

root = tk.Tk()
url = "http://imgs.xkcd.com/comics/python.png"

with urllib.request.urlopen(url) as connection:
    raw_data = connection.read()
im = Image.open(io.BytesIO(raw_data))
image = ImageTk.PhotoImage(im)

widget = tk.Label(root, image=image)
widget.grid(row=0,column=0)

root.mainloop()

Answer 1

所以你的问题是因为image函数一结束就被删除，而tkinter需要保存图像以供某处引用。你知道吗

我们可以通过global或将图像返回到全局函数中定义的变量来实现这一点。你知道吗

选项1 global：

import tkinter as tk
import urllib.request
from PIL import Image, ImageTk
import io


def ImgFromUrl(url):
    global image
    with urllib.request.urlopen(url) as connection:
        raw_data = connection.read()
    im = Image.open(io.BytesIO(raw_data))
    image = ImageTk.PhotoImage(im)
    return image

root = tk.Tk()
url = "http://imgs.xkcd.com/comics/python.png"
widget = tk.Label(root, image=ImgFromUrl(url))
widget.grid(row=0, column=0)

root.mainloop()

选项2将图像对象返回到全局命名空间中定义的变量：

import tkinter as tk
import urllib.request
from PIL import Image, ImageTk
import io


def ImgFromUrl(url):
    with urllib.request.urlopen(url) as connection:
        raw_data = connection.read()
    im = Image.open(io.BytesIO(raw_data))
    image = ImageTk.PhotoImage(im)
    return image

root = tk.Tk()
url = "http://imgs.xkcd.com/comics/python.png"
image = ImgFromUrl(url)
widget = tk.Label(root, image=image)
widget.grid(row=0, column=0)

root.mainloop()