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Re: feTurbulence with filter primitive subregions

From: Erik Dahlström <ed@opera.com>
Date: Mon, 12 May 2008 14:31:54 +0200
To: robert@ocallahan.org, www-svg <www-svg@w3.org>
Message-ID: <op.ua1jrggjgqiacl@gnorps.palace.opera.no>

On Sun, 11 May 2008 09:24:01 +0200, Robert O'Callahan  
<robert@ocallahan.org> wrote:

> It's not clear to me from the spec what the 'point' parameter of the
> 'turbulence' function means.
>
> Suppose I have
> <filter primitiveUnits="userSpaceOnUse" x="0" y="0" width="20"  
> height="20">
>   <feTurbulence x="10" y="10" width="10" height="10"/>
> </filter>
>
> When we compute 'turbulence' for the top-left corner of the feTurbulence
> filter primitive subregion, what is 'point'? I assume it's either (0,0)  
> or (0.5,0,5).

I think that should depend on how an implemention does sampling in  
general. It's unlikely that an error would be easy to spot in most cases  
though.

> Also, I think one can deduce that 'fTileX', 'fTileY', 'fTileWidth' and
> 'fTileHeight' are the bounds of the filter primitive subregion, but it  
> would
> be helpful if that was documented.

Absolutely. And yes, that is how I interpret these parameters as well.

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 Monday, 12 May 2008 12:30:29 GMT

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