- From: Erik Dahlstrom <ed@opera.com>
- Date: Tue, 06 Apr 2010 10:26:29 +0200
- To: "SVG Working Group WG" <public-svg-wg@w3.org>
On Fri, 02 Apr 2010 17:49:19 +0200, SVG Working Group Issue Tracker <sysbot+tracker@w3.org> wrote: > > ISSUE-2317 (feGaussianBlur stdDeviation=0): Give different result for > feGaussianBlur stdDeviation=0 [SVG Full 1.1] > > http://www.w3.org/Graphics/SVG/WG/track/issues/2317 > > Raised by: Doug Schepers > On product: SVG Full 1.1 ... > Opera and Firefox both handle this correctly (according to the spec). > But it > seems to me the spec is a bit too fussy. It is written, I presume, to > avoid a > problem of dividing by zero in the definition of the blur function: > > H(x) = exp(-x2/ (2s2)) / sqrt(2* pi*s2) > > But when you think of it this way: more standarddeviation means more > blur. Zero > standard deviation should mean no blur. > The issue arose when I wanted to use script to append a blur filter onto > an > object and allow a slider to control the amount of blur. Rather than > removing > the filter attribute from the DOM I just wanted to change StdDev to > zero. Alas, > while ASV knew what I wanted to do, Opera and FF followed the spec. I > think this > attribute is only used in feGaussian blur, but even if it were used in > other > contexts, I do think that authors will think zero means "no > variability", not > "turn the image black and make it transparent" > > Is this the sort of thing that should be raised here, in SVG IG, or with > SVG WG, > or with a nontrivial subset of the three? > ]] I agree that it's more intuitive to let stdDeviation="0 0" mean that the filter just returns the filter input unchanged (that is: no blur applied), and that having e.g stdDeviation="25,0" should mean that the blur is only applied in the direction where there's a non-zero value. I have ACTION-2189 to clarify this in the filters spec. /Erik -- Erik Dahlstrom, Core Technology Developer, Opera Software Co-Chair, W3C SVG Working Group Personal blog: http://my.opera.com/macdev_ed
Received on Tuesday, 6 April 2010 08:27:04 UTC