如何在图像上绘制矩形框；wxPython？

import wx

class MyFrame(wx.Frame):
    def __init__(self, parent, title):
        super(MyFrame, self).__init__(parent, title=title, size=(400, 300))
        self.Bind(wx.EVT_PAINT, self.OnPaint)
        
    def OnPaint(self, event):
        dc = wx.PaintDC(self)
        dc.SetPen(wx.Pen(wx.RED, 2))  # 设置画笔颜色和线宽
        dc.SetBrush(wx.Brush(wx.TRANSPARENT))  # 设置填充颜色为透明
        
        # 绘制矩形框
        rect = wx.Rect(50, 50, 200, 150)  # 矩形框的位置和大小
        dc.DrawRectangle(rect)
        
app = wx.App()
frame = MyFrame(None, "绘制矩形框示例")
frame.Show()
app.MainLoop()