https://bugs.winehq.org/show_bug.cgi?id=46287
--- Comment #6 from Anton Romanov theli.ua@gmail.com --- Confirming that native gdiplus fixes this issue.
So, to summarize the issue is that:
* wine gdiplus does not recognize WMF files starting with 01000900 * wine gdiplus GdipSaveImageToStream won't save WMF as PNG (or any other format, really)