feDisplacement filter -- problem with spec and image quality

Hi folks,

 

Compare this page in Chrome and Firefox (Windows).

 

 <http://cs.sru.edu/~ddailey/svg/distortGrid0.svg>
http://cs.sru.edu/%7Eddailey/svg/distortGrid0.svg Compare both speed and
image quality.
 
You'll note that Firefox performs much faster. I am told [1] that this is
because "Firefox on Windows uses Direct2D IIRC, and the filters are
accelerated." The speed issue should be handled later, according to the
Chrome folks.
 
The troublesome thing, though, is the image quality. Observe the crispness
of the edges in Firefox and the truly inadequate rendering in Chrome. When I
raised the issue as a Chrome bug [1] the folks there did a goodly amount of
research on the history of the problem and it seems to be a spec bug rather
than a browser bug, introduced when the filters module was split out from
the rest. (I'm so not in favor of having 29 different specs and Working
Groups - it's always a prime number -- to talk to when I find a problem with
SVG that wasn't there before!)

 

I made a slightly simplest version here:
http://cs.sru.edu/~ddailey/svg/distortGrid.svg without some of the aesthetic
niceties. 

 

I gather it comes from not specifying how the feDisplacement's effect on its
results will be resampled. 

 

Ultimately, if an feDisplacement is applied to a vector image, we might,
alternatively, approach the problem by doing a convolution of the respective
functions (applying the continuous Perlin noise, functionally, to the
associated curves themselves, resulting in vector rather than pixel-based
output - but the math here could get gnarly - I don't know. ) At any rate,
having a flexible set of distortion filters that preserves vectors would be
a good thing to think about for SVG3, if it's not already in the wish lists.
Having a bitmap at the core of spherical distortion [2] in the test cases
seems a bit like a hack to me!

 

In the  meantime, can we require feDisplacement to do a little better? It's
not only a problem when vectors are distorted - note how the bitmaps crack
and separate using Chrome here:
https://ello.co/ddailey/post/iagdm_myjtpdy9dyvsoozq

I can report that this sort of cracking didn't happen in Adobe's ASV, nor in
Opera during its SVG-, so this is, indeed moving back to <SVG1.1.  - of
course the examples that used to work in ASV and Opera heyday (remember the
fried egg-billiards and the face distorted by pond ripples from 2005?) no
longer work anywhere (due to other manifestations of "progress" - I think I
used enable-background or some such thing, since in those days you could!).

 

Regards

David

[1] https://bugs.chromium.org/p/chromium/issues/detail?id=634115

[2] http://cs.sru.edu/~ddailey/svg/feComposite9.svg