Re: [svgwg] Poor interop of `<feComposite operator="arithmetic">` with large k values (#1046)

`feComposite` is now being handled by the css wg. 
https://drafts.fxtf.org/filter-effects/#feCompositeElement

`operator="arithmetic"`
https://drafts.csswg.org/filter-effects-1/#element-attrdef-fecomposite-operator

> The compositing operation that is to be performed. All of the [operator](https://drafts.csswg.org/filter-effects-1/#element-attrdef-fecomposite-operator) types except arithmetic match the corresponding operation as described in [[COMPOSITING-1]](https://drafts.csswg.org/filter-effects-1/#biblio-compositing-1) with [in](https://drafts.csswg.org/filter-effects-1/#element-attrdef-filter-primitive-in) representing the source and [in2](https://drafts.csswg.org/filter-effects-1/#element-attrdef-fecomposite-in2) representing the destination. The arithmetic operator is described above.
>
> The [initial value](https://svgwg.org/svg2-draft/types.html#TermInitialValue) for [operator](https://drafts.csswg.org/filter-effects-1/#element-attrdef-fecomposite-operator) is [over](https://drafts.csswg.org/filter-effects-1/#attr-valuedef-fecomposite-operator-over).

The above definition is:


>If the arithmetic operation is chosen, each result pixel is computed using the following formula:
>
> result = k1*i1*i2 + k2*i1 + k3*i2 + k4
> where:
> 
> i1 and i2 indicate the corresponding pixel channel values of the input image, which map to [in](https://drafts.csswg.org/filter-effects-1/#element-attrdef-filter-primitive-in) and [in2](https://drafts.csswg.org/filter-effects-1/#element-attrdef-fecomposite-in2) respectively
k1, k2, k3 and k4 indicate the values of the attributes with the same name

@fantasai @smfr should this be handled in discussions by the CSS WG?



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Received on Wednesday, 7 January 2026 03:20:50 UTC