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Re: [fxtf-drafts] [filters-1] filter region and filter primitive subregion should be defined better for CSS filter functions

From: Amelia Bellamy-Royds via GitHub <sysbot+gh@w3.org>
Date: Sat, 10 Jun 2017 16:45:52 +0000
To: public-fxtf-archive@w3.org
Message-ID: <issue_comment.created-307576588-1497113150-sysbot+gh@w3.org>
It might be useful to add a note in the "Filter primitive representation" section for `blur()` and `drop-shadow()`, pointing down to the "Filter region for shorthands" section.  The SVG equivalents as given are not fully accurate for those shorthands, since there is currently no way to represent this automatic calculation in the longhand notation.  

But beyond that, I'm fine with keeping this in prose for now.  The exact calculation would depend on how far you extend the blur effect (it is theoretically infinite, like a Gaussian curve, but is clamped at a reasonable distance).  The [definition of `<feGaussianBlur>`](https://drafts.fxtf.org/filters/#feGaussianBlurElement) gives some recommendations, but does not require a specific algorithm or degree of precision.  I assume most implementations clamp the effect to max 3 standard deviations, some might clamp it to 2 standard deviations (aka 1 "blur radius").

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Received on Saturday, 10 June 2017 16:45:59 UTC

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