There are APIs for most of it, the only step that has to be done manually is premultiplying the alpha channel. (changing the image from A,R,G,B to A,R*A,G*A,B*A)

The problem is that there're two completely different APIs, one for solid and one for transparent, and the transparent one only works on Win2k and XP (and it's less familiar to most coders). Most modules currently use the solid API, and you need to have code for both if the module is to work on Win9x.

If LSAPI provided a uniform interface for this, it would make it much simpler to support alpha, but it would be such a huge change that you'd be back to rewriting all the modules.