[pygame] convert transparent region to white

[Chuang Wu]

Hi there,

I have a 64x64 icon with transparent region. I wanna show the transparent region in *white* color.

If I use convert_alpha(), the transparent region doesn't show. if I just use convert(), it became black.

So How to make it white? it'll be great if the image can have a black edge too =D

Thanks,
CC