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Topic: Re: 1.4 spec - compositing
Conf: (P-PDF) Developers, Msg: 56178
From: LeonardR
Date: 5/29/2002 05:17 PM

At 05:19 PM 8/27/2001 -0400, p-pdf-developer Listmanager wrote:
>Does anyone know how to interpret the "group alpha", "group shape" and
>"group color" as referred to in section 5.3 of the 1.4 spec?

First of all, you should be careful with implementing the 1.4
compositing additions, since many of them are still covered by non-licensed
Adobe patents.

>It is difficult to determine how a single value for alpha, shape and color
>(per channel) can be attributed to an object that can have varying
>backdrops, depending on what object(s) it overlays.

You might want to take a gander at the GhostScript 7 sources, as
Raph Levien has done a pretty good job implementing most of that stuff -
even though few (if any) real world examples exist.


Leonard Rosenthol
Director of Software Development (215) 922-3509 (voice)
Appligent, Inc. (formerly Digital Applications) (610) 284-4233 (fax)

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