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[REBOL] Re: Face Transparency?

From: rotenca:telvia:it at: 18-Nov-2002 18:10

Holger words: "Previously the effect pipeline had an undocumented side effect, that if the face was transparent and did not have an image, the effects would not apply to the face, but rather to the background behind the face. This would allow you to create faces that act as filters. Because of the implied transparency caused by alpha channels, this side effect no longer exists, i.e. an effect always applies to the image itself, never to the background. You can still create faces that act as filters, but you need to tell the system about that. The effect keyword for that is "merge". It can appear anywhere in an effect block, but will most commonly appear at the beginning. What "merge" does is merge the image currently in the pipeline with the background behind the face, using alpha-based compositing. The result is then used as the current pipeline image. If there is no current image then just the background itself is used. For instance, if you previously used [colorize 255.0.0] to colorize the background behind a face red you now have to use [merge colorize 255.0.0]." --- Ciao Romano