[fxtf-drafts] [filter-effects] SVG filter for invert not working properly (#462)

blakegearin has just created a new issue for https://github.com/w3c/fxtf-drafts:

== [filter-effects] SVG filter for invert not working properly ==
Hello, I noticed that the [SVG filter for `invert`](https://www.w3.org/TR/filter-effects-1/#invertEquivalent) does not appear to be working properly.

```html
<feComponentTransfer>
  <feFuncR type="table" tableValues="[amount] (1 - [amount])"/>
  <feFuncG type="table" tableValues="[amount] (1 - [amount])"/>
  <feFuncB type="table" tableValues="[amount] (1 - [amount])"/>
</feComponentTransfer>
```

An amount of `0.5` appears over-lighten. Unless I'm mistaken that an `amount` of `0.5` is equivalent to a CSS filter's `50%`...?

I found that using `feFuncA` instead of `feFuncR`, `feFuncG`, and `feFuncB` appears to work correctly.

```html
<feComponentTransfer>
  <feFuncA type="table" tableValues="[amount] (1 - [amount])"/>
</feComponentTransfer>
```

Comparison:

```html
<p>Original Color</p>
<div style=""></div>
<p>CSS filter invert</p>
<div class="base"></div>
<p>SVG filter invert on W3</p>
<div class="base" style="filter: url(#w3-invert)"></div>
<p>SVG filter invert with feFuncR</p>
<div class="base" style="filter: url(#feFuncR-invert)"></div>
<svg>
  <filter id="w3-invert">
    <feComponentTransfer>
      <feFuncR type="table" tableValues=".5 .5"/>
      <feFuncG type="table" tableValues=".5 .5"/>
      <feFuncB type="table" tableValues=".5 .5"/>
    </feComponentTransfer>
</filter>
</svg>
<svg>
  <filter id="feFuncR-invert">
    <feComponentTransfer>
      <feFuncA type="table" tableValues=".5 .5"/>
    </feComponentTransfer>
  </filter>
</svg>

<style>
.base {
  height: 100px; 
  width: 100px; 
  background-color: #000000;  
}
</style>
```

Image preview:

<img width="228" alt="image" src="https://user-images.githubusercontent.com/17950836/180668956-abb7e76c-8388-4bd8-88e2-81374ac57f88.png">




Please view or discuss this issue at https://github.com/w3c/fxtf-drafts/issues/462 using your GitHub account


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Received on Sunday, 24 July 2022 23:04:39 UTC