http://bugs.winehq.org/show_bug.cgi?id=23708
--- Comment #5 from Vincent Povirk madewokherd@gmail.com 2010-08-26 14:56:13 --- Um, I'm pretty sure you'll need to create a new stream containing just the PNG data. This would ideally be accomplished using IWICStream::InitializeFromIStreamRegion, but that's not implemented yet.