http://bugs.winehq.org/show_bug.cgi?id=27499
--- Comment #2 from Damjan Jovanovic damjan.jov@gmail.com 2011-06-17 02:09:50 CDT --- (In reply to comment #1)
What's stopping you from using WIC to decode other image formats the same way as ICO?
Winemenubuilder extracts the best quality icons for each icon size. WIC doesn't provide any information about colors for each icon index (it lies they're all 32 BPP ARGB on Wine and native), hence winemenubuilder has to parse the ICONDIR manually. This won't work for a BMP file, and it's done in at least 3 places. It seems like the cleanest solution to convert to ICO first and then work with that.