如何无需先打开任意图片即可使用ImageTk.getimage？

调用ImageTk.getimage处理图片时触发如下错误：

line 279, in getimage
photo.tk.call("PyImagingPhotoGet", photo, block.id)
tkinter.TclError: invalid command name "PyImagingPhotoGet"

奇怪的是：如果先对任意图片执行一次ImageTk.PhotoImage调用，后续ImageTk.getimage就能正常工作。

以下是可复现问题的示例代码：

from tkinter import *
from PIL import ImageTk, Image
import os

gamma_code =  'R0lGODlhCgAMAIcAAP///9v//4/b////22a2////trZmAN'
gamma_code += 'uPOTmP29vb/wAAALb//7aPj7ZmZrZmOf+2Zo+2j49mj485'
gamma_code += 'OY85AP/bj2ZmOWYAOWYAANv/2zk5jzkAAABmtgA5jwAAZg'
for k in range(90) : gamma_code +=  'AAAAAAAAAA'
gamma_code += 'AAACH5BAEAAAAALAAAAAAKAAwAAAhgAAEIHEgQAAUNHRYA'
gamma_code += 'OKCAAAAADDBIEFDgAgEAAAYkAGCAwIENAEKKdAAhQwAAKF'
gamma_code += 'M2qCAAgMuXAAwgAECzJoABEQIA2MkTwAMOAQAIHTpgAgIA'
gamma_code += 'SJMCKGBBAICnUKNKBRAQADs='

LAMBDA_code =  'R0lGODlhDQANAIcAAP///wAAAP//ttuPOWYAAP+2Zo/b/'
LAMBDA_code += '2a2/9v//wAAOQBmtrb//wA5j485AP//2//bj7ZmAI85Zm'
LAMBDA_code += 'ZmtrZmOTmP2zmPtjk5jwAAZgAAAAAAA'
for m in range(92) : LAMBDA_code +=  'AAAAAAAAAA'
LAMBDA_code += 'CH5BAEAAAAALAAAAAANAA0AAAiDAAEIHEiw4EABEgAoXM'
LAMBDA_code += 'gQwIALCwBInDjRQYMABwBo3LixQIUGDBAAGEly5AQDAxI'
LAMBDA_code += 'YAMCyJYAHFhAIIEABgM2bAAYcAAAAAgMEAIIGdRBhAQAA'
LAMBDA_code += 'BQIcAMCUaQEFAKIKIKAAgFUAAggcAMAVwIAEBgAAEEAgQ'
LAMBDA_code += 'AIDAAAUCMBWAYC3cOPGDQgAOw=='

def test(IM) :
    try :
        ImageTk.getimage(IM)
        print('SUCCESS')
    except : print('FAILURE')    
    

root = Tk()
A = PhotoImage(data = gamma_code)
print('image 1 dimensions : ',A.width(),',',A.height())

B = PhotoImage(data = LAMBDA_code)
print('image 2 dimensions : ',B.width(),',',B.height())

temp_file_name = 'wlqdkijqodmqqx9.f4r' #random digits
B.write(temp_file_name)    

print('\nattempt 1 : ', end = "")
test(A)

ImageTk.PhotoImage(Image.open(temp_file_name))
print("\n'ImageTk.PhotoImage(Image.open(temp_file_name))' has now been run.")

print('attempt 2 : ', end = "")
test(A)

os.remove(temp_file_name)

原因与解决方法 #

原因 #

ImageTk.getimage依赖的Tcl命令PyImagingPhotoGet并未在程序启动时自动注册。只有当第一次调用ImageTk.PhotoImage时，模块才会完成Tcl扩展的初始化，注册该命令，后续getimage才能正常调用。

解决方案 #

不需要实际加载图片，只需提前触发ImageTk的初始化逻辑即可。在程序启动阶段添加以下代码：

from tkinter import Tk
from PIL import ImageTk

root = Tk()
# 触发ImageTk的Tcl扩展初始化
ImageTk._get_image_tk(root)

或者更简单的方式，直接调用一次空的ImageTk.PhotoImage（无需传入图片），但_get_image_tk方法更直接对应初始化逻辑，推荐使用。

执行一次初始化后，后续所有ImageTk.getimage调用都会正常工作，无需再临时调用PhotoImage。

内容的提问来源于stack exchange，提问作者agat