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Re: patternTransform

From: Domenico Strazzullo <nst@dotuscomus.com>
Date: Mon, 3 Oct 2011 15:05:54 +0200
Message-ID: <064011D48825411A981E2BD5B906D4A9@RAPAX>
To: "Dirk Schulze" <vbs85@gmx.de>
Cc: <www-svg@w3.org>
Am 03.10.2011 um 12:14 schrieb Domenico Strazzullo:

>> I read in the specification that the patternTransform attribute:
>> "contains the definition of an optional additional transformation from 
>> the pattern coordinate system onto the target coordinate system .
>> This additional transformation matrix is post-multiplied ",
>> and:
>> "If attribute 'patternTransform' is not specified, then the effect is as 
>> if an identity transform were specified. ".
>> What's an identity transform? Does it mean that if patternTransform is 
>> specified,  implementations are allowed to bitmap the tile and re-sample 
>> it?
>> That's the impression I have with Opera, Firefox and Webkit. From what I 
>> can see, only IE9 seems to apply transformations correctly.
>> The result is kind of acceptable in Opera and Firefox, but really bizarre 
>> in Webkit.
>> You can check some results here:
>> http://dotuscomus.com/pergola/download/pergola_1.3.6/ExamplesHTML/Patterns/patterns.html
>> Domenico

> You should specify your question. I assume you mean the pixelation on the 
> pattern tiles.

Yes. The question was: "Does it mean that if patternTransform is specified, 
implementations are allowed to bitmap the tile and re-sample it?".
I was also asking: "What's an identity transform?".

> IIRC all implementations try to avoid pixelated tiles. And normally it 
> works quite well.
> I haven't checked why Opera, Firefox and WebKit fail on your example yet.
> But ideally patterns should never look pixelated, independent of the 
> pattern transform, viewBox
> or other transformations. In realty all these implementations work with 
> bitmaped tiles.

So they seem, except IE9 (and perhaps ASV, which I haven't tested). But in 
the specification I don't read anywhere in the concerned section that 
patternTransform is
 "implementation dependent". I would assume then that to bitmap a pattern 
tile *before* applying transformations, and then re-sample according to the 
transformation values, breaks the specification. In any case, the fact of 
pre-bitmapping takes away the low level control needed by the developer 
and/or the artist.


> Thats the way most (all?) graphic libraries work.

> Greetings
> Dirk 
Received on Monday, 3 October 2011 13:06:26 UTC

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