- From: Simon Fraser via GitHub <noreply@w3.org>
- Date: Thu, 01 Jan 2026 20:17:28 +0000
- To: public-svg-issues@w3.org
smfr has just created a new issue for https://github.com/w3c/svgwg:
== Poor interop of <feComposite operator="arithmetic"> with large k values ==
Mozilla's ref [test analyzer](https://wpt.live/common/third_party/reftest-analyzer.xhtml) uses SVG filters to highlight differences between two images. One filter primitive is:
```
<feComposite result="c" in="c1" in2="c2" operator="arithmetic" k2="255" k3="255"/>
```
The arithmetic operator has poor interop, possibly because of rounding issues. Test case:
```
<filter id="filter" filterUnits="objectBoundingBox" x="0" y="0" width="100%" height="100%">
<feFlood x="10" y="10" width="200" height="200" flood-color="rgb(128, 10, 0)" flood-opacity="0.5" result="first" />
<feFlood x="100" y="100" width="200" height="200" flood-color="rgb(10, 128, 0)" flood-opacity="1" result="second" />
<feComposite in="first" in2="second" operator="arithmetic" k2="255" k3="255" />
</filter>
```
This gives different results in each major browser:
<img width="1697" height="749" alt="Image" src="https://github.com/user-attachments/assets/caa97c70-2851-45bf-b7a8-cf1aa66b2661" />
Chrome's results even change based on the screen color profile.
Please view or discuss this issue at https://github.com/w3c/svgwg/issues/1046 using your GitHub account
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Received on Thursday, 1 January 2026 20:17:29 UTC