Copy a bitmap

There is an old post suggests that to properly a bitmap you should
first convert it to image then convert it back to bitmap.
Is it correct? or we have a new method available in latest version.

I gave a try to these, prior to above method but none of these to
seems to properly copy a bitmap. Loosing transparency or completely
black etc.

newbitmap = copy.copy( oldbitmap )
newbitmap = oldbitmap.GetSubBitmap( wx.Rect( 0, 0, oldbitmap.GetWidth
(), oldbitmap.GetHeight() ) )

Prashant
Python 2.6.2
wxPython 2.8.10.1