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Re: min/max values for filters

From: Erik Dahlstrom <ed@opera.com>
Date: Fri, 12 Nov 2010 08:48:36 +0100
To: public-svg-wg@w3.org
Message-ID: <op.vl1ry7jjgeuyw5@localhost>
On Fri, 12 Nov 2010 01:14:16 +0100, Patrick Dengler <patd@microsoft.com>  
wrote:

> We have been looking at the filters chapter and believe that there would  
> be a benefit for setting min/max for some of the attributes.  We are  
> recommending these as currently, without these bounds, most browsers  
> would likely peg the CPU so badly, it would lead it to be inoperable, or  
> are reasonable limits a developer would want or a  user could perceive.   
> We'd like to see these expressed in a future version of the filters  
> specification, but would like to see it documented.
>
> feConvolveMatrix:  Order (Kernel Units)	
> Min : (1, 1)
> Max: (10, 10)	

Min (1,1) is already the case for 'order', integers greater than 0 is what  
the spec requires.

> feConvolveMatrix, feSpecularlighting , feDiffuseLighting: Kernel Unit  
> Length 	
> Min: 0.1
> Max: 10
>
> feMorphology: Radius
> Max: 150
>
> feTurblulance: numOctaves
> Max: 10
>
> Any input is appreciated.

I don't think it's unreasonable to let implementations clamp these values  
to something that provides an similar result but with lower computation  
cost. It's probably not a bad idea to at least add some informative notes  
in the spec for these cases (we already have some but they could be made a  
bit more visible, and we could have some actual examples with e.g the  
min,max-ranges you suggest here).

The question is whether the spec should define/require the min,max values  
in absolute terms since e.g on a mobile phone one might prefer to trade  
off a larger share of the rendering quality for speed than on a desktop pc.

Could you raise this as an issue in the tracker, with product "SVG Filters  
1.2"?

Cheers
/Erik

-- 
Erik Dahlstrom, Core Technology Developer, Opera Software
Co-Chair, W3C SVG Working Group
Personal blog: http://my.opera.com/macdev_ed
Received on Friday, 12 November 2010 07:49:13 GMT

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