Add raw bitmap access sample to the demo

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@40860 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

wxPython/demo/BitmapFromBuffer.py

@@ -77,7 +77,7 @@ class TestPanel(wx.Panel):
         # Make a bitmap using an array of RGB bytes plus a separate
         # buffer for the alpha channel
         bpp = 3  # bytes per pixel
-        bytes = array.array('B', [1,2,3] * width*height)#*bpp)
+        bytes = array.array('B', [0] * width*height*bpp)
 
         def offset(x, y):
             # return the offset into the bytes array for the start of