python-3.x - 使用 matplotlib 和 tkinter 的透明背景

Question

我正在为 whatsapp 聊天编写数据分析程序，我的 tkinter 窗口中有一个 matplotlib 图。我知道如何自定义颜色，但如何将背景设置为透明？

f = Figure(figsize=(4.1, 4.1), dpi=100)                                        
f.set_facecolor('xkcd:gray')                   # this should be transparent
a = f.add_subplot(111)
a.plot(dates, mes_count)
a.xaxis.set_major_locator(MaxNLocator(prune='both',nbins=6))
a.set_facecolor('xkcd:gray')

canvas = FigureCanvasTkAgg(f, mainloop.root)                                    
canvas.get_tk_widget().place(x=190, y=80)

Answer 1

尝试将轴/图形的背景颜色与每个平台上的 tkinter 应用程序的背景颜色相匹配时，我感到有点沮丧，所以我做了一些挖掘:

一般来说，需要做两件事:

1. 通过将 facecolor 设置为“none”，告诉 matplotlib 为图形和轴对象使用透明背景:

   f.set_facecolor("none")
   a.set_facecolor("none")
   

2. 告诉后端渲染器也使背景透明，例如将其保存为 png:

   f.savefig('mygraph.png', transparent=True)
   

问题是:如何将此告诉 FigureCanvasTkAgg？ Looking at the sourcecode of FigureCanvasTk ，绘制时，可以看到 tk.Canvas 始终使用白色背景创建。 AFAIK Canvas 不能是透明的(请纠正我)，但是当在没有特定背景颜色的情况下创建时，它将具有与其周围的框架相同的背景颜色，由 ttk.Style 给出它。所以我可以想到两种解决方法:

1. 创建FigureCanvasTkAgg后，将 Canvas 的背景色设置为与当前样式相同:

    s = ttk.Style()
    bg = s.lookup("TFrame", "background")
    bg_16bit = self.winfo_rgb(bg)
    bg_string = "#" + "".join([hex(bg_color >> 8)[2:] for bg_color in bg_16bit])
    canvas.get_tk_widget().config(bg=bg_string)
   

   第 3 和第 4 行是必需的，例如Windows，因为s.lookup("TFrame", "background") can return a system color name here , 然后需要将其转换为标准的 #aabbcc 十六进制颜色

2. 制作您自己的 MyFigureCanvasTk 这只是 matplotlib 中代码的一个副本，跳过设置 Canvas 的背景颜色:

    class MyFigureCanvasTk(FigureCanvasTk):
   
        # Redefine __init__ to get rid of the background="white" in the tk.Canvas
        def __init__(self, figure=None, master=None):
            super().__init__(figure)
            self._idle_draw_id = None
            self._event_loop_id = None
            w, h = self.get_width_height(physical=True)
            self._tkcanvas = tk.Canvas(
                master=master,
                #background="white"
                width=w,
                height=h,
                borderwidth=0,
                highlightthickness=0,
            )
            self._tkphoto = tk.PhotoImage(master=self._tkcanvas, width=w, height=h)
            self._tkcanvas.create_image(w // 2, h // 2, image=self._tkphoto)
            self._tkcanvas.bind("<Configure>", self.resize)
            if sys.platform == "win32":
                self._tkcanvas.bind("<Map>", self._update_device_pixel_ratio)
            self._tkcanvas.bind("<Key>", self.key_press)
            self._tkcanvas.bind("<Motion>", self.motion_notify_event)
            self._tkcanvas.bind("<Enter>", self.enter_notify_event)
            self._tkcanvas.bind("<Leave>", self.leave_notify_event)
            self._tkcanvas.bind("<KeyRelease>", self.key_release)
            for name in ["<Button-1>", "<Button-2>", "<Button-3>"]:
                self._tkcanvas.bind(name, self.button_press_event)
            for name in ["<Double-Button-1>", "<Double-Button-2>", "<Double-Button-3>"]:
                self._tkcanvas.bind(name, self.button_dblclick_event)
            for name in ["<ButtonRelease-1>", "<ButtonRelease-2>", "<ButtonRelease-3>"]:
                self._tkcanvas.bind(name, self.button_release_event)
   
            # Mouse wheel on Linux generates button 4/5 events
            for name in "<Button-4>", "<Button-5>":
                self._tkcanvas.bind(name, self.scroll_event)
            # Mouse wheel for windows goes to the window with the focus.
            # Since the canvas won't usually have the focus, bind the
            # event to the window containing the canvas instead.
            # See https://wiki.tcl-lang.org/3893 (mousewheel) for details
            root = self._tkcanvas.winfo_toplevel()
            root.bind("<MouseWheel>", self.scroll_event_windows, "+")
   
   
    class MyFigureCanvasTkAgg(FigureCanvasAgg, MyFigureCanvasTk):
        def draw(self):
            super().draw()
            self.blit()
   
        def blit(self, bbox=None):
            _backend_tk.blit(
                self._tkphoto, self.renderer.buffer_rgba(), (0, 1, 2, 3), bbox=bbox
            )
   

这样我们就可以让图形与周围可能存在的任何背景颜色融为一体。它应该适用于所有平台(仅在 Windows 和 Linux 上测试，使用 python 3.11，tkinter 8.6.12)。也许这可以帮助遇到这个问题的人。