http://bugs.winehq.org/show_bug.cgi?id=17308
--- Comment #11 from Vincent Povirk madewokherd@gmail.com 2009-09-05 12:32:07 --- It's not using gdiplus to draw, just to load images in RGBA format. http://www.winehq.org/pipermail/wine-patches/2009-September/078124.html may help.
GdipGetImageRawFormat would also be nice to implement (and should be possible now that decoders are in place), but I don't think it'll help.