Custom alpha for standard window?

FROM : Tim Conkling
DATE : Wed Nov 03 20:02:06 2004

I'm interested in applying a custom alpha channel to a standard window.
I know that it's possible to call setAlphaValue: to set the a single
alpha value for the whole window, but I'm interested in modifying the
alpha on a per-pixel basis. Is this possible without creating a custom
window shape?

Thanks,
Tim