PS/PDF API Change Proposal: (Re: [cairo] Semantics of transparent objects)

Keith Packard keithp at
Fri Jan 20 12:03:57 PST 2006

On Fri, 2006-01-20 at 08:43 -0800, Carl Worth wrote:

> As we've mentioned, in "common" usage there won't be a difference in
> the two modes. The difference shows up only when the user starts using
> the more elaborate operators (DEST_OUT say). And when would a user
> actually use the operators? My claim is that they are only useful when
> destination alpha is available, so they will "only" appear in code
> that is expecting destination alpha.

Ok, I think this is enough justification to support only COLOR_ALPHA as
the 'usual' PS/PDF content and make people who really do want the COLOR
results for operators which generally involve dest alpha to create a
similar surface. Of course, this presupposes the existance of non-image
based COLOR to COLOR_ALPHA meta surface copies, but we want that in any
keith.packard at
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