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[filters] notes to CSS filters

From: Dirk Schulze <vbs85@gmx.de>
Date: Thu, 22 Sep 2011 12:15:17 +0200
Message-Id: <CFA1CC7E-45E1-4670-A14E-EDF5474BB8BB@gmx.de>
To: public-fx@w3.org
Just some notes after reading Filters 1.0 [1]:

The feUnsharpMask seems to be one of the shorthand filters (like feDropShadow). Other than feDropShadow it does not describe how you can reach the same result on using the previously defined effects, nor does the effect have an algorithm yet. I guess this will be fixed in one of the next revisions.

The example for feImage misses an image. Some other effects have a link to an example, but the example is missing as well. I'm sure that this will be fixed in a future version, just want to mention it.

Which color space will CSS filters support? Right now, SVG Filters is using linearRGB. But linearRGB is not specified within CSS IIRC. Also CSS supports DeviceRGB (default) as well as sRGB [2] (you can test it on WebKit with -webkit-color-correction). Will SVG have to support DeviceRGB as well?

For the current CSS shorthand filter effects it is quite easy to omit filter regions. The implementations can calculate the boundaries  
themselves. What is the status on the SVG part? Do we find a way to limit the filter region size automatically? Right now one of the filter effects that can have unlimited size is lightning (same for feTurbulence IIRC).
However, Firefox limits the size of a lighting effect automatically! You'll see that if you compare the example [3] between Firefox and Chrome/Opera. The size of the filter result on Firefox is smaller. Even if it is a bug in Firefox at the moment, we could add a rule to the filter specification that would specify this behavior. Once we've done that, we can omit filterRegions (or make it optional) and don't need to auto clip to (-10%, -10%, 120%, 120%) anymore.
(Firefox takes the size of the previous filter effect and uses the same size for the lighting effect if no subregion was specified).

Dirk

[1] https://dvcs.w3.org/hg/FXTF/raw-file/tip/filters/publish/Filters.html
[2] http://dev.w3.org/csswg/css-color-correction/
[3] http://trac.webkit.org/export/95704/trunk/LayoutTests/svg/dynamic-updates/SVGFEPointLightElement-dom-y-attr.html
Received on Thursday, 22 September 2011 10:15:48 GMT

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