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Re: SVG filters feOffset and primitiveUnits

From: Robert O'Callahan <robert@ocallahan.org>
Date: Sat, 13 Jun 2009 22:21:31 +1200
Message-ID: <11e306600906130321k50e5a6cfubea7ea8d7950af90@mail.gmail.com>
To: Dirk Schulze <vbs85@gmx.de>
Cc: www-svg@w3.org
On Sat, Jun 13, 2009 at 4:37 AM, Dirk Schulze <vbs85@gmx.de> wrote:

> I have a question to feOffset in SVG filters
> ( http://www.w3.org/TR/SVG11/filters.html#feOffset ).
> dx and dy depend on primitiveUnits. But what does it mean?
> Does it mean that if primitiveUnits is objectBoundingBox, the number
> given to dx and dy are interpreted as percentage or still as "pixel"?

objectBoundingBox units are described here:

> Then, coordinate (0,0) in the new user coordinate system is mapped to the
> (minx,miny) corner of the tight bounding box within the user coordinate
> system of the applicable element and coordinate (1,1) in the new user
> coordinate system is mapped to the (maxx,maxy) corner of the tight bounding
> box of the applicable element.

I notice that Opera agrees with Batik in treating dx/dy numbers as
user-space units, but I'm still pretty sure we (Firefox) are right according
to the spec, when we interpret 0.25 the same as 25% of the way across the
object bounding box.

I agree that this behaviour is very unintuitive and the spec made a
regrettable decision here. objectBoundingBox units would be a lot more
useful if percentages referred to the bounding box and numbers were still
interpreted as user-space units. However, objectBoundingBox units are used a
lot and I doubt their behaviour can be changed without breaking content.

"He was pierced for our transgressions, he was crushed for our iniquities;
the punishment that brought us peace was upon him, and by his wounds we are
healed. We all, like sheep, have gone astray, each of us has turned to his
own way; and the LORD has laid on him the iniquity of us all." [Isaiah
Received on Saturday, 13 June 2009 10:22:04 UTC

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