Why is this code not accepting this png images transparency?

I've isolated the cause of the problem to be the image, since the code seems to work with other png images with transparency. However, it doesn't seem to work with the one image I need it to. This would be of great help seeing as I'm trying to make a nice shaped window.

The image:

The code:

import wx

class PictureWindow(wx.Frame):
    def __init__(self, parent, id, title, pic_location):

        # For PNGs. Must be PNG-8 for transparency...
        self.bmp = wx.Image(pic_location, wx.BITMAP_TYPE_PNG).ConvertToBitmap()

        framesize = (self.bmp.GetWidth(), self.bmp.GetHeight())

        # Launch a frame the size of our image. Note the position and style stuff...
        # (Set pos to (-1, -1) to let the OS place it.
        # This style wx.FRAME_SHAPED is a frameless plain window.
        wx.Frame.__init__(self, parent, id, title, size=framesize, pos = (50, 50), style = wx.FRAME_SHAPED)

        r = wx.RegionFromBitmap(self.bmp)
        self.SetShape(r)

        # Define the panel and place the pic
        panel = wx.Panel(self, -1)
        self.mainPic = wx.StaticBitmap(panel, -1, self.bmp)

        # Set an icon for the window if we'd like
        #icon1 = wx.Icon("icon.ico", wx.BITMAP_TYPE_ICO)
        #self.SetIcon(icon1)

        self.Show()

        # The paint stuff is only necessary if doing a shaped window
        self.Bind(wx.EVT_PAINT, self.OnPaint)
        self.Main()


    def OnPaint(self, event):
        dc = wx.PaintDC(self)
        dc.DrawBitmap(self.bmp, 0, 0, True)

    def Main(self):
        sizer = wx.GridBagSizer()
        button = wx.Button(self,-1,label="Click me !")
        sizer.Add(button, (0,1))


# What pic are we opening?
pic_location = r"C:\Users\user\Pictures\CPUBAR\A4.png" # PNG must be png-8 for             transparency...

app = wx.App(redirect=0) # the redirect parameter keeps stdout from opening a wx gui window
PictureWindow(None, -1, 'Picture Viewer', pic_location)
app.MainLoop()

This is in Windows 7, btw.

wx.RegionFromBitmap uses the bitmap's mask to set the shape. If your source image has an alpha channel then it won't have a mask and so wx.RegionFromBitmap will not be able to determine what shape to use. You can convert the source image such that all pixels are either fully opaque or fully transparent, and then wx.Image will load it with a mask instead of an alpha channel. Or you can convert it at runtime using wx.Image's ConvertAlphaToMask method before converting it to a wx.Bitmap.