CSS - mask-composite

Example

#masked {
  width: 100px;
  height: 100px;
  background-color: #8cffa0;
  mask-image: url(https://mdn.mozillademos.org/files/12668/MDN.svg),
              url(https://mdn.mozillademos.org/files/12676/star.svg);
  mask-size: 100% 100%;
  mask-composite: add; /* Can be changed in the live sample */
}

<div id="masked">
</div>
<select id="compositeMode">
  <option value="add">add</option>
  <option value="subtract">subtract</option>
  <option value="intersect">intersect</option>
  <option value="exclude">exclude</option>
</select>

var clipBox = document.getElementById("compositeMode");
clipBox.addEventListener("change", function (evt) {
  document.getElementById("masked").style.maskClip = evt.target.value;
});

Syntax  

/* Keyword values */
mask-composite: add;
mask-composite: subtract;
mask-composite: intersect;
mask-composite: exclude;

/* Global values */
mask-composite: inherit;
mask-composite: initial;
mask-composite: unset;

Values

For the composition the current mask layer is referred to as source, while all layers below it are referred to as destination.

add

The source is placed over the destination.

subtract

The source is placed, where it falls outside of the destination.

intersect

The parts of source that overlap the destination, replace the destination.

exclude

The non-overlapping regions of source and destination are combined.

Formal syntax

<a href="css/mask-composite#compositing-operator"><compositing-operator></a><a href="css/value_definition_syntax#hash_mark_(.23)" title="Hash mark">#</a><p>where <br><code><compositing-operator> = add <a href="css/value_definition_syntax#single_bar" title="Single bar">|</a> subtract <a href="css/value_definition_syntax#single_bar" title="Single bar">|</a> intersect <a href="css/value_definition_syntax#single_bar" title="Single bar">|</a> exclude</code></p>

Description  

The mask-composite CSS property represents a compositing operation used on the current mask layer with the mask layers below it.

Browser Compatibility  

[1] WebKit and Blink have a -webkit-mask-composite property, which has different keywords.

[2] This feature is not implemented yet. See bug 1251161.

Specifications  

License