- From: SVG Working Group Issue Tracker <sysbot+tracker@w3.org>
- Date: Fri, 2 Apr 2010 15:49:19 +0000 (GMT)
- To: public-svg-wg@w3.org
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 >From David Dailey <http://tech.groups.yahoo.com/group/svg-developers/message/63595>: [[ The spec (1.1) says: [...] A value of zero disables the effect of the given filter primitive (i.e., the result is a transparent black image). If the attribute is not specified, then the effect is as if a value of 0 were specified. ------------- 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? ]] Reply from Doug Schepers <http://tech.groups.yahoo.com/group/svg-developers/message/63606>: [[ Interestingly, I ran into this very issue this past weekend. I agree with you... the effects of values should be intuitive, especially when being iterated though via script (this is why I think arc segments should still render when the start and end points are the same). Illustrator, whence come the filters, also agrees with you, though Inkscape follows the SVG spec. I think this is something that should be changed, since there are differences in implementations. If you wouldn't mind resending your message to www-svg, I'll remember to raise it in discussion with the SVG WG. ]]
Received on Friday, 2 April 2010 15:49:20 UTC