wxPython Background image on frame

MMGP Answerd but wont let me credit him right ;-) So I will at least mention him here. (And I did finally get to credit him... 8-)

His linked discussion on Double Buffering provided a base code that worked with the following modifications:

Insert this beginning at line 106 (overwritting existing code until you get to the last line shown here):

    # Here's the actual drawing code.
    cliWidth, cliHeight = self.GetClientSize()
    bmp=wx.Bitmap("Logo16x9.png")
    bmpWide = bmp.GetWidth()
    bmpHeight = bmp.GetHeight()
    img = bmp.ConvertToImage()
    scaleFactor = cliWidth/bmpWide
    bmp = wx.BitmapFromImage(img.Scale(int(bmpWide * scaleFactor), int(bmpHeight * scaleFactor)))
    bmpWide = bmp.GetWidth()
    bmpHeight = bmp.GetHeight()
    xPos = (cliWidth - (bmpWide))/2
    yPos = (cliHeight - (bmpHeight))/2
    # altered by me
    dc.DrawBitmap(bmp, xPos, yPos)


class TestFrame(wx.Frame):

I've been beating my head against this all day.

I'm new to drawing graphics with the wxPython modules, and when I needed to draw a background image on a frame I found this code which works well if the image is the full size of the window.

However, I need to place a company logo as the background, and have it remain centered through resizes. In it's current form the resize causes a graphic artifact the size of a small nation to appear on the screen with any resize event.

The logo image file (used on line 43 of the code) is a 400x300 (WxH) image.

I am looking for a way to either: resize my image on the fly to match wx.GetClientSize(), or a way to avoid/remove the artifact. Preferably without involving PIL or ImageMagick. App has to function on a local level only, and be system agnostic (Win, Lin and Mac), none of this involves network activities or mapped drives.

Python 2.7 and wxPython 2.8

The code I am using (with my modification annotated) is as follows:

import wx

########################################################################
class MainPanel(wx.Panel):
    """"""

    #----------------------------------------------------------------------
    def __init__(self, parent):
        """Constructor"""
        wx.Panel.__init__(self, parent=parent)
        self.SetBackgroundStyle(wx.BG_STYLE_CUSTOM)
        self.frame = parent

        sizer = wx.BoxSizer(wx.VERTICAL)
        hSizer = wx.BoxSizer(wx.HORIZONTAL)

        for num in range(4):
            label = "Button %s" % num
            btn = wx.Button(self, label=label)
            sizer.Add(btn, 0, wx.ALL, 5)
        hSizer.Add((1,1), 1, wx.EXPAND)
        hSizer.Add(sizer, 0, wx.TOP, 100)
        hSizer.Add((1,1), 0, wx.ALL, 75)
        self.SetSizer(hSizer)
        self.Bind(wx.EVT_ERASE_BACKGROUND, self.OnEraseBackground)

    #----------------------------------------------------------------------
    def OnEraseBackground(self, evt):
        """
        Add a picture to the background
        """
        # yanked from ColourDB.py
        dc = evt.GetDC()
        # Added by me
        cliWidth, cliHeight = self.GetClientSize()

        if not dc:
            dc = wx.ClientDC(self)
            rect = self.GetUpdateRegion().GetBox()
            dc.SetClippingRect(rect)
        dc.Clear()
        # use a 400x300 image
        bmp = wx.Bitmap("Logo4x3.png")
        # added by me
        xPos = (cliWidth - 400)/2
        yPos = (cliHeight - 300)/2
        # altered by me
        dc.DrawBitmap(bmp, xPos, yPos)
        #dc.DrawBitmap(bmp, 0, 0)

########################################################################
class MainFrame(wx.Frame):
    """"""

    #----------------------------------------------------------------------
    def __init__(self):
        """Constructor"""
        wx.Frame.__init__(self, None, size=(600,450))
        panel = MainPanel(self)        
        self.Center()

########################################################################
class Main(wx.App):
    """"""

    #----------------------------------------------------------------------
    def __init__(self, redirect=False, filename=None):
        """Constructor"""
        wx.App.__init__(self, redirect, filename)
        dlg = MainFrame()
        dlg.Show()

#----------------------------------------------------------------------
if __name__ == "__main__":
    app = Main()
    app.MainLoop()

Update: Latest Failure - Modified lines 37 to 52

if not dc:
    dc = wx.ClientDC(self)
    rect = self.GetUpdateRegion().GetBox()
    dc.SetClippingRect(rect)
dc.Clear()
# use a 400x300 image
bmp = wx.Bitmap("Logo4x3.png")
img = bmp.ConvertToImage()
scaleFactor = cliWidth/400
bmp = wx.BitmapFromImage(img.Scale(int(400*scaleFactor),int(300*scaleFactor)))
# added by me
#xPos = (cliWidth - 400)/2
#yPos = (cliHeight - 300)/2
# altered by me
#dc.DrawBitmap(bmp, xPos, yPos)
dc.DrawBitmap(bmp, 0, 0)

Another attempt and another fail. No difference in the output to screen. Additionally, the referenced document on double buffering does not address this issue, but does suffer from the same result. This code modifies lines 36 through 57 of the original.

brsh = wx.Brush('#000000')


if not dc:
    dc = wx.ClientDC(self)
    rect = self.GetUpdateRegion().GetBox()
    dc.SetClippingRect(rect)
dc.SetBackground(brsh)
dc.SetDeviceOrigin(0,0)
dc.DestroyClippingRegion()
dc.Clear()
# use a 400x300 image
bmp = wx.Bitmap("Logo4x3.png")
img = bmp.ConvertToImage()
scaleFactor = cliWidth/400
bmp = wx.BitmapFromImage(img.Scale(int(400*scaleFactor),int(300*scaleFactor)))
# added by me
#xPos = (cliWidth - 400)/2
#yPos = (cliHeight - 300)/2
# altered by me
#dc.DrawBitmap(bmp, xPos, yPos)
dc.DrawBitmap(bmp, 0, 0)

From the comments I suggested using double buffered drawing, but I didn't see that in the edited post. Also, I had several drawing issues when self.SetBackgroundStyle(wx.BG_STYLE_CUSTOM) was used. But this line might be helpful in other systems beyond mine, so I wanted to keep it. So, in order to handle the situation, here is a updated code that uses double buffered drawing and works fine here:

import wx

class MainPanel(wx.Panel):
    def __init__(self, parent, bg_img='Logo4x3.png'):
        wx.Panel.__init__(self, parent=parent)
        self.SetBackgroundStyle(wx.BG_STYLE_CUSTOM)
        self.bg = wx.Bitmap(bg_img)
        self._width, self._height = self.bg.GetSize()

        sizer = wx.BoxSizer(wx.VERTICAL)
        hSizer = wx.BoxSizer(wx.HORIZONTAL)

        for num in range(4):
            btn = wx.Button(self, label="Button %s" % num)
            sizer.Add(btn, 0, wx.ALL, 5)
        hSizer.Add((1,1), 1, wx.EXPAND)
        hSizer.Add(sizer, 0, wx.TOP, 100)
        hSizer.Add((1,1), 0, wx.ALL, 75)
        self.SetSizer(hSizer)
        self.Bind(wx.EVT_SIZE, self.OnSize)
        self.Bind(wx.EVT_PAINT, self.OnPaint)
        self.Bind(wx.EVT_ERASE_BACKGROUND, self.OnEraseBackground)

    def OnSize(self, size):
        self.Layout()
        self.Refresh()

    def OnEraseBackground(self, evt):
        pass

    def OnPaint(self, evt):
        dc = wx.BufferedPaintDC(self)
        self.Draw(dc)

    def Draw(self, dc):
        cliWidth, cliHeight = self.GetClientSize()
        if not cliWidth or not cliHeight:
            return
        dc.Clear()
        xPos = (cliWidth - self._width)/2
        yPos = (cliHeight - self._height)/2
        dc.DrawBitmap(self.bg, xPos, yPos)

app = wx.App()
frame = wx.Frame(None, size=(400,300))
panel = MainPanel(frame)
frame.Show()
app.MainLoop()

The method OnEraseBackground is intentionally empty.