How to Capture Contents of a Window

I'm using wxPython 2.4.1.2 on Windows NT SP 6. I've got a 3rd
party library that draws some pictures for me. It works fine
for drawing what it should. I do something like:

  import ctypes
  ThirdPartyDLL = ctypes.windll.LoadLibrary("Some.Dll")

  aHandle = someWxWindow.GetHandle()
  ThirdPartyDLL.DrawAPictureOn(aHandle)

This all works, but how can I use wxPython to grab a copy of
the picture after it gets drawn??? For example, when I resize
a window, all the controls refresh and the drawing is lost.
If I could get it a bitmap or such, I could plaster it back
over something, or whatever.

Any way to do this correctly?

TIA

I don't see any way in the wxPython docs, so I'm going to prowl
through the win32api docs to see what's there.

Al