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Re: mask: luminance or alpha

From: Brian Birtles <birtles@gmail.com>
Date: Tue, 31 Jul 2012 10:37:46 +0900
Message-ID: <501736EA.8030805@gmail.com>
To: www-svg@w3.org
(2012/07/31 8:13), Rik Cabanier wrote:
> Last week, there was a decision to have the id-less mask have ‘alpha’ as
> the default instead of ‘luminance’

The decision was to make masks that refer to non-<mask> content default 
to alpha. It's not related to id-less referencing.

There are two orthogonal changes here:

1) Allowing referencing the mask source without using IDs
2) Allowing referencing mask source content that isn't a <mask>

For (1) nothing changes. The 'auto' value for the mask type (i.e. alpha 
vs luminance) is based on the maskType attribute of the <mask> element 
which defaults to luminance.

For (2) we decided to make 'auto' behave as alpha since it seems like a 
lot of people want to refer to a raster image as their mask and use the 
alpha values as the mask values. I'm pretty sure that's how -webkit-mask 

With regards to (2), I don't have a strong preference for the default 
behaviour. I can see good arguments for both.

Best regards,


PS- I'm currently adding these changes to the spec. I've yet to check 
them in because I'm trying to work out how the positioning should work 
for (2) but I'll hopefully check something in in the next day or two 
which will make this discussion a little more concrete.
Received on Tuesday, 31 July 2012 01:38:18 UTC

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