Re: turbulence filters

jf barraud wrote:
> ...
> I suspect we are using premultiplied alpha where normal colors should be
> used, but I remember I already bumped into similar strongly non
> intuitive conventions of svg with this respect (maybe the same one, I
> don't remember), so I'm not sure.

No, it's not a premultiplied/non-premultiplied issue (btw, in the
standard, if it doesn't say it's non-premultiplied it is premultiplied,
it says so in section 15.7.1 of SVG 1.1). Rather, it has to do with
Inkscape's lack of support for the color-interpolation-filters attribute
(in combination with the extremely unintuitive decision to give
color-interpolation-filters a different initial value than
color-interpolation).

In SVG there are two attributes that determine the color space used for
operating on color values, these are color-interpolation and
color-interpolation-filters (both can be set to either linearRGB or
sRGB). For some reason that is completely beyond me the W3C decided to
make the initial value sRGB for color-interpolation and linearRGB for
color-interpolation-filters... As Inkscape has no support whatsoever for
color-interpolation-filters pretty much any file which uses a filter
looks wrong in Inkscape.

To ensure that your file looks the same in Inkscape as in other viewers,
use color-interpolation-filters="sRGB" (as far as I know it's perfectly
valid to do this just once, on the root SVG element). I've attached a
file that shows how Batik renders filters-turb-01-f.svg with this
modification.


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