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Re: [1.2T-LC] inverse and constrained transformations (ISSUE-2073)

From: Anthony Grasso <anthony.grasso@cisra.canon.com.au>
Date: Fri, 10 Oct 2008 17:19:08 +1000
Message-ID: <48EF01EC.4070208@cisra.canon.com.au>
To: "Dr. Olaf Hoffmann" <Dr.O.Hoffmann@gmx.de>
CC: www-svg@w3.org

Hi Dr. Hoffmann,

Excellent find in the specification! The SVG Working Group discussed this issue 
and we concluded that we should add wording that warns authors of the problem.

As a result I was given ACTION-2284 [1] to add the wording to the specification. 
The new wording can be found in "The TransformRef value" [2] section of the 

Please advise the SVG Working Group if you have any further comments or feedback 
regarding this issue.

Kind Regards,

[1] http://www.w3.org/Graphics/SVG/WG/track/actions/2284
[2] http://dev.w3.org/SVG/profiles/1.2T/publish/coords.html#transform-ref

Doug Schepers wrote:
> Hi, Dr. Olaf-
> Thanks for your comment.  We will discuss it and get back to you soon.
> Regards-
> -Doug
> Dr. Olaf Hoffmann wrote (on 9/27/08 11:53 AM):
>> Hello SVG WG,
>> the section 7.7 about constrained transformations mentions
>> several times the inverse of the CTM. Obviously this does
>> not always exist (if the determinant is zero).
>> Is it really intended, that this inverse matrix is used by 
>> implementations to get the desired effect or is it expected, 
>> that the effect is gained with other methods (what should be 
>> always possible even without using the not always existing 
>> inverse matrix, because the document contains much more 
>> information about the transformations than only the CTM)?
>> But if it is really expected, that the inverse matrix
>> is used, what is the expected behaviour, if it does not exist,
>> for example for a short time within an animation or due to
>> some tricky things using the vector-effect non-scaling-stroke.
>> To mention this would be important especially for authors,
>> because then they have to compute and avoid such situations.
>> If another method is used, they do not really have to care.
>> Olaf
Received on Friday, 10 October 2008 07:19:58 UTC

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