Re: How much background content gets blurred by feGaussianBlur

Hi David,

If the kernel of the gaussian blur picks color data outside of the filter primitives boundaries, Opera and WebKit take transparent black, while Firefox takes the pixel data of the closest  pixel on the primitive boundaries. The new specification is more clear about this IMO. All unspecified pixels (all pixels that are not covered by the primitive boundaries for example), are set to transparent black according to the Filter Effects 1.0 specification[1] . Note that the filter primitive boundaries get clipped by the filter boundaries as well.

So the behavior of Opera, WebKit and ASV is correct according to the new specification, while the old specification was not clear about that.

Greetings,
Dirk

[1] http://dvcs.w3.org/hg/FXTF/raw-file/3f1fdd4a8004/filters/publish/Filters.html#FilterPrimitivesOverviewIntro

> I’m not quite sure what to expect here.
>  
> http://granite.sru.edu/~ddailey/svg/backgroundBlur.svg
>  
> In this example two blurry patches are placed above some content. One patch has not had its filter restricted in scope, the other has had the filter confined by
>  
> <filter id="H" x="5%" y="5%" width="90%" height="90%">
>  
> Opera, Chrome and ASV render the overall result on left and right roughly the same. The opacity of the center of the ellipses at left and right are basically equivalent.
>  
> FF makes the confined patch, on right, considerably more opaque than the one on the left.
>  
> I think this is due to disallowing null pixels (white) from outside the primitive filter coordinates from being averaged into the overall result, since they are “out of bounds.” The other browsers apparently do not see it the same way.