Member GetSubImageWithAlpha (const wxImage &Src, const wxRect &rect): in wxWidgets, wxImage::GetSubImage should do this itself.
Member ThemeBase::LoadOneThemeComponents (teThemeType id, bool bOkIfNotFound=false): (wxWidgets) A png may have been saved with alpha, but when you load it, it comes back with a mask instead! (well I guess it is more efficient). Anyway, we want alpha and not a mask, so we call InitAlpha, and that transfers the mask into the alpha channel, and we're done.