Tkinter拼接两个背景图Label时如何消除连接处的灰色边框

问题效果截图

问题成因 #

灰色边框并非Label默认边框，核心诱因有三点：

• 承载内容的second_frame父容器指定错误，原代码将其挂载到main_frame下，而非实际要显示内容的canvas，导致控件尺寸、布局边距计算异常
• pack()布局默认会给相邻控件预留微小间距，未显式置零时间距会露出底层控件的默认灰色背景
• 承载背景图的Label、内容父容器未设置和图片边缘一致的背景色，一旦出现1px级别的渲染缝隙，就会透出默认灰色底

修复步骤 #

• 修正second_frame的父容器为canvas，同时将其背景色设置为和背景图边缘一致的蓝色，从容器层避免露底
• 给两个背景Label的pack()方法显式添加pady=0、padx=0参数，消除布局默认间距
• 给两个承载背景图的Label添加和图片边缘同色的bg属性，就算出现极微渲染偏差也不会露出灰色
• （推荐）提前用PIL将两张背景图拼接为单张长图，用单个Label加载，从根源上规避多控件拼接的缝隙问题

修正后核心代码 #

基础修复（保留双Label方案） #

# 修正second_frame父容器为canvas，添加同色背景
second_frame = Frame(canvas, height = Canvasheight*8, width = Canvaswidth, borderwidth=0, highlightthickness =0, relief= 'flat', bg='#9ad0f0') 

# Add new frame to a window in the canvas
canvas.create_window((0,0), window = second_frame, anchor='nw', width= Canvaswidth)
second_frame.pack_propagate(False)

####################################### THE BACKGROUND IMAGES
img1 = ImageTk.PhotoImage(Image.open("Screenshot 2022-06-28 at 10.29.24 AM.png"))
# 给Label添加同色背景，pack时显式置零边距
label1 = Label(second_frame, image = img1, borderwidth=0, highlightthickness =0, relief= 'flat', bg='#9ad0f0')
label1.pack(pady=0, padx=0)

img2 = ImageTk.PhotoImage(Image.open("Screenshot 2022-06-28 at 10.29.24 AM.png"))
label2 = Label(second_frame, image = img2, borderwidth=0, highlightthickness =0, relief= 'flat', bg='#9ad0f0')
label2.pack(pady=0, padx=0)

优化方案（单图拼接，彻底规避缝隙） #

# 提前拼接两张背景图
bg1 = Image.open("Screenshot 2022-06-28 at 10.29.24 AM.png")
bg2 = Image.open("Screenshot 2022-06-28 at 10.29.24 AM.png")
total_h = bg1.height + bg2.height
total_w = max(bg1.width, bg2.width)
combined_bg = Image.new("RGB", (total_w, total_h))
combined_bg.paste(bg1, (0, 0))
combined_bg.paste(bg2, (0, bg1.height))
img_total = ImageTk.PhotoImage(combined_bg)

# 单Label加载整图
bg_label = Label(second_frame, image=img_total, borderwidth=0, highlightthickness=0, relief='flat', bg='#9ad0f0')
bg_label.pack(pady=0, padx=0)

内容的提问来源于stack exchange，提问作者Tharushi