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[SVG1.1F2 LC] previous discussion about filterRes

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Tue, 29 Jun 2010 18:48:05 +0200
To: www-svg@w3.org
Message-Id: <201006291848.05359.Dr.O.Hoffmann@gmx.de>
Hello www-svg,

I think, the previous discussion about filterRes could be reflected 
within the related section, for example as an informative addition.

Previous discussion:
http://lists.w3.org/Archives/Public/www-svg/2009Jul/0014.html
http://lists.w3.org/Archives/Public/www-svg/2009Jul/0017.html
http://lists.w3.org/Archives/Public/www-svg/2009Jul/0020.html
http://lists.w3.org/Archives/Public/www-svg/2009Jul/0029.html

Summary:
a) Problem with float numbers and rounding in implementations

Suggestion: 
Note, that behaviour for float numbers is undefined,
therefore authors should use only integers. 
Note furthermore, that this might cause implementation dependent
behaviour for continuous animation, in doubt authors have to
use discrete animation providing all intended values manually.

Alternatively define the behaviour for float numbers.

b) To which value in pixels results the mentioned 'default' of 400dpi? 
What does 'current display's pixel resolution' mean?
For example, if the filter region is related to an area of 1000px x 600px
device pixels, is the related value '1000 600'?
Or does it mean for the same device with a display of 1600px x 1200px
a value of '1600 1200'?

Suggestion: 
Explain how to derive the required number value
for filterRes from the mentioned '400dpi default'.

Alternatively avoid to mention units for an attribute value,
that can only contain numbers.

Provide an example for a device display and a filter region
as mentioned.


Best wishes 

Olaf
Received on Tuesday, 29 June 2010 16:56:38 GMT

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