[svgwg] Issue: 'color-interpolation' isn't used for alpha compositing marked as Needs removal

• From: Chris Lilley via GitHub <sysbot+gh@w3.org>
• Date: Mon, 15 Oct 2018 14:24:12 +0000
• To: public-svg-issues@w3.org
• Message-ID: <issues.labeled-273959164-None-sysbot+gh@w3.org>

svgeesus has just labeled an issue for https://github.com/w3c/svgwg as "Needs removal":

== 'color-interpolation' isn't used for alpha compositing ==
The [definition](https://www.w3.org/TR/SVG/painting.html#ColorInterpolationProperty) of `color-interpolation` states:

> The ‘color-interpolation’ property specifies the color space for ... alpha compositing.

However, it appears that no implementations actually do this.

Here is the test file. In an implementation which follows the spec wording, the apparent color of the circles should be different.

```svg
<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C/DTD SVG 1.1//EN"  "http://www.w3.org/Graphics.SVG/1.1/DTD/svg11.dtd">
<svg version="1.1" xmlns="http://www.w3.org/2000/svg">
    <rect x="0" y="0" width="100" height="100" fill="white" stroke="red"/>
    <circle cx="50" cy="50" r="30" fill="black" opacity="0.5"/>
    <g color-interpolation="sRGB">
        <rect x="100" y="0" width="100" height="100" fill="white" stroke="red"/>
        <circle cx="150" cy="50" r="30" fill="black" opacity="0.5"/>
    </g>
    <g color-interpolation="linearRGB">
        <rect x="200" y="0" width="100" height="100" fill="white" stroke="red"/>
        <circle cx="250" cy="50" r="30" fill="black" opacity="0.5"/>
    </g>
</svg>
```

And here are screenshots of the implementations:
![capture-3](https://user-images.githubusercontent.com/918903/32807181-e191939e-c943-11e7-93b6-1a93d7ac18f4.PNG)
<img width="1280" alt="screen shot 2017-11-14 at 1 47 55 pm" src="https://user-images.githubusercontent.com/918903/32807182-e1ad0822-c943-11e7-8899-0315bf076623.png">

See https://github.com/w3c/svgwg/issues/366

Received on Monday, 15 October 2018 14:24:13 UTC