在 tkinter 画布上绘制矩形不起作用

Question

我试图在 tkinter 中画布内的图像上绘制一个简单的矩形，但它没有绘制。没有错误。

是因为我放置图像时没有使用

canvas.create_image

吗？因为我正在框架内绘制图像，并将框架放置在画布内。这是通过滚动功能打开完整图像的唯一方法。

这是代码：

import tkinter as tk
from PIL import ImageTk, Image

root = tk.Tk()

# Tkinter widgets needed for scrolling. The only native scrollable container that Tkinter provides is a canvas.
# A Frame is needed inside the Canvas so that widgets can be added to the Frame and the Canvas makes it scrollable.
canvas = tk.Canvas(root)
fTable = tk.Frame(canvas)
hor_scroll_bar = tk.Scrollbar(root)
ver_scroll_bar = tk.Scrollbar(root)

# Updates the scrollable region of the Canvas
def updateScrollRegion():
    canvas.update_idletasks()
    canvas.config(scrollregion=fTable.bbox())

# Sets up the Canvas, Frame, and scrollbars for scrolling
def createScrollableContainer():
    canvas.config(xscrollcommand=hor_scroll_bar.set,yscrollcommand=ver_scroll_bar.set, highlightthickness=0)
    hor_scroll_bar.config(orient=tk.HORIZONTAL, command=canvas.xview)
    ver_scroll_bar.config(orient=tk.VERTICAL, command=canvas.yview)

    hor_scroll_bar.pack(fill=tk.X, side=tk.BOTTOM, expand=tk.FALSE)
    ver_scroll_bar.pack(fill=tk.Y, side=tk.RIGHT, expand=tk.FALSE)
    canvas.pack(fill=tk.BOTH, side=tk.LEFT, expand=tk.TRUE)
    canvas.create_window(0, 0, window=fTable, anchor=tk.NW)

# Adding an image 
def addNewLabel():
    img = ImageTk.PhotoImage(file="test.jpg")
    tk.Label(fTable, image=img).grid(row=0, column=0)
    canvas.img = img
    canvas.create_rectangle(0, 0, 100, 100, fill="blue")
    # Update the scroll region after new widgets are added
    updateScrollRegion()

createScrollableContainer()
addNewLabel()

root.mainloop()

谢谢你

Answer 1

问题似乎与您尝试在画布上绘制矩形的方式有关。使用包含可滚动框架的画布时，绘制形状时必须使用相对于画布本身而不是框架的坐标。

下面，您将找到 addNewLabel() 函数的调整版本：

def addNewLabel():
    img = ImageTk.PhotoImage(file="test.jpg")
    label = tk.Label(fTable, image=img)
    label.grid(row=0, column=0)
    # Save a reference to the image to prevent it from being garbage collected
    label.img = img
    canvas.create_rectangle(10, 10, 110, 110, fill="blue")  # Coordinates relative to the canvas
    # Update the scroll region after new widgets are added
    updateScrollRegion()

我已经将 create_rectangle 函数的坐标调整为相对于画布。尝试一下修改后的代码，您应该会观察到画布上绘制的蓝色矩形。请随意微调坐标，将矩形精确定位在您想要的位置。