mask-composite

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

Initial value	add
Applies to	all elements; In SVG, it applies to container elements excluding the <defs> element and all graphics elements
Inherited	no
Media	visual
Computed value	as specified
Animation type	discrete
Canonical order	the unique non-ambiguous order defined by the formal grammar

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

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

Example

CSS Content

#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 */
}

Specifications

Specification	Status	Comment
CSS Masking Level 1 The definition of 'mask-composite' in that specification.	Candidate Recommendation	Initial definition

Browser compatibility

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

[2] This feature is not implemented yet. It is only available in Nightly and Dev Edition. See bug 1251161.