gluing together 4 bitmaps

1. Create a destination wxEmptyBitmap of the right size
2. create a wxMemoryDC
3. memdc.SelectObject(destbmp)
4. use memdc.DrawBitmap with each of the source bitmaps at the desired positions
5. memdc.SelectObject(wxNullBitmap)
6. destbmp.SaveFile

Thank you, u are real wxgenius:)