自适应的背景图片

import wx


class MyPanel(wx.Frame):
    def __init__(self):
        wx.Frame.__init__(self, None, -1)
        self.SetBackgroundStyle(wx.BG_STYLE_ERASE )
        self.Bind(wx.EVT_ERASE_BACKGROUND, self.OnEraseBackground)  
        self.Bind(wx.EVT_SIZE,self.onSize)
    
        self.bg_img=wx.Image("images/bg.gif")
        
    def OnEraseBackground(self, evt):
            dc = evt.GetDC()
     
            if not dc:
                dc = wx.ClientDC(self)
                rect = self.GetUpdateRegion().GetBox()
                dc.SetClippingRect(rect)
            dc.Clear()
    
            self.StretchBackground(dc)

    def StretchBackground(self, dc): 
            sz = self.GetClientSize()
            image = self.bg_img.Scale(sz.x,sz.y)
            bg_bmp = image.ConvertToBitmap()
            dc.DrawBitmap(bg_bmp, 0, 0)
            

        
    def onSize(self,evt):
        self.Refresh()
#       evt.Skip()
        
if __name__ == '__main__':
    app = wx.PySimpleApp()
    frame = MyPanel()
   
    frame.Show()
    app.MainLoop()
import wx


class MyPanel(wx.Frame):
    def __