mask-composite

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

/* 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;

Syntax

One or more of the keyword values listed below, separated by commas.

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 definition

Formal syntax

<compositing-operator>#
where 
<compositing-operator> = add | subtract | intersect | exclude

Examples

Compositing mask layers with addition

CSS

#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.maskComposite = evt.target.value;
});

Result

Specifications

Browser compatibility