2010/2/5 Vincent Povirk <madewokherd+8cd9@gmail.com>

It's supported 32bpp with transparency from the start. The full list
of supported writing formats is here:
http://source.winehq.org/source/dlls/windowscodecs/pngformat.c#L680

GUID_WICPixelFormat32bppBGRA is the format you want, I think.

You probably tried to use a format not on that list, which defaults to
24-bit. I'm not sure what the behavior should be in that case.

That's odd. Both WIC and winemenubuilder appear to be using BGR for
32-bit pixel formats and informing libpng of this . I don't know where
you could be getting RGB pixels.