tkinter.ttk.Treeview根节点图标/图像不出现

Problem:我无法让图标图像出现在 tkinter.ttk.Treeview 中根节点旁边。下面是我使用的测试代码。它执行时没有错误，但图像没有出现在根节点的左侧。我尝试过使用图像文件的完整路径名，但这不起作用。另外，我尝试使用 PIL.ImageTk.PhotoImage 打开图像文件，但这也不起作用。相反，出现了如下所示的错误。

问题：如何让图标图像出现在 tkinter.ttk.Treeview 根节点（或任何节点）的左侧？

测试代码：

import os
import tkinter as tk
import tkinter.ttk as ttk
from PIL import Image, ImageTk

class App(ttk.Frame):

    def __init__(self, master, path):
    ttk.Frame.__init__(self, master)
    self.tree = ttk.Treeview(self)
    ysb = ttk.Scrollbar(self, orient='vertical', command=self.tree.yview)
    xsb = ttk.Scrollbar(self, orient='horizontal', command=self.tree.xview)
    self.tree.configure(yscroll=ysb.set, xscroll=xsb.set)
    self.tree.heading('#0', text='Directory', anchor='w')

    abspath = os.path.abspath(path)
    i = './icon/Home-icon_16.gif'
    root_pic = tk.PhotoImage(file=i)
    #root_pic = ImageTk.PhotoImage(i)
    root_node = self.tree.insert('', 'end', text=abspath, open=True, image=root_pic)
    l1_node = self.tree.insert(root_node, 'end', text='level 1', open=True)
    l2_node = self.tree.insert(l1_node, 'end', text='level 2', open=True)
    l3_node = self.tree.insert(l2_node, 'end', text='level 3', open=True)
    l2a_node = self.tree.insert(l1_node, 'end', text='level 2a', open=True)
    l3a_node = self.tree.insert(l2a_node, 'end', text='level 3a', open=True)

    self.tree.grid(row=0, column=0)
    ysb.grid(row=0, column=1, sticky='ns')
    xsb.grid(row=1, column=0, sticky='ew')
    self.grid()

root = tk.Tk()
path_to_my_project = os.getcwd()
app = App(root, path=path_to_my_project)
app.mainloop()

使用 PIL.ImageTk.PhotoImage 时出现错误消息：

root_pic = ImageTk.PhotoImage(i)
  File "/usr/lib/python3/dist-packages/PIL/ImageTk.py", line 108, in __init__
    mode = Image.getmodebase(mode)
  File "/usr/lib/python3/dist-packages/PIL/Image.py", line 296, in getmodebase
    return ImageMode.getmode(mode).basemode
  File "/usr/lib/python3/dist-packages/PIL/ImageMode.py", line 52, in getmode
    return _modes[mode]
KeyError: './icon/Home-icon_16.gif'

Home-icon_16.gif:

应用：python3.5 ver3.5.1-10; python3-tk ver3.5.1-1； tk8.6 ver8.6.5-1； python3-pil.imagetk:amd64 ver3.1.2-0ubuntu1

首先尝试创建 PIL 图像Image.open('file_path')然后做Photoimage。另外，您需要保留对 PhotoImage 的引用，否则它不会在 tkinter 中显示。

import os
import tkinter as tk
import tkinter.ttk as ttk
from PIL import Image, ImageTk

class App(ttk.Frame):

    def __init__(self, master, path):
        ttk.Frame.__init__(self, master)
        self.tree = ttk.Treeview(self)
        ysb = ttk.Scrollbar(self, orient='vertical', command=self.tree.yview)
        xsb = ttk.Scrollbar(self, orient='horizontal', command=self.tree.xview)
        self.tree.configure(yscroll=ysb.set, xscroll=xsb.set)
        self.tree.heading('#0', text='Directory', anchor='w')

        abspath = os.path.abspath(path)
        i = './icon/Home-icon_16.gif'
        root_pic1 = Image.open(i)                           # Open the image like this first
        self.root_pic2 = ImageTk.PhotoImage(root_pic1)      # Then with PhotoImage. NOTE: self.root_pic2 =     and not     root_pic2 =

        root_node = self.tree.insert('', 'end', text=abspath, open=True, image=self.root_pic2)
        l1_node = self.tree.insert(root_node, 'end', text='level 1', open=True)
        l2_node = self.tree.insert(l1_node, 'end', text='level 2', open=True)
        l3_node = self.tree.insert(l2_node, 'end', text='level 3', open=True)
        l2a_node = self.tree.insert(l1_node, 'end', text='level 2a', open=True)
        l3a_node = self.tree.insert(l2a_node, 'end', text='level 3a', open=True)

        self.tree.grid(row=0, column=0)
        ysb.grid(row=0, column=1, sticky='ns')
        xsb.grid(row=1, column=0, sticky='ew')
        self.grid()

root = tk.Tk()
path_to_my_project = os.getcwd()
app = App(root, path=path_to_my_project)
app.mainloop()