CSS - mask-mode

Example

#masked {
  width: 227px;
  height: 200px;
  background: blue linear-gradient(red, blue);
  mask-image: url(https://mdn.mozillademos.org/files/12668/MDN.svg);
  mask-mode: alpha; /* Can be changed in the live sample */
}

<div id="masked">
</div>
<select id="maskMode">
  <option value="alpha">alpha</option>
  <option value="luminance">luminance</option>
  <option value="match-source">match-source</option>
</select>

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

Syntax  

/* Keyword values */
mask-mode: alpha;
mask-mode: luminance;
mask-mode: match-source;

/* Multiple values */
mask-mode: alpha, match-source;

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

Values

alpha

This keyword indicates that the transparency (alpha channel) values of the mask layer image should be used as the mask values.

luminance

This keyword indicates that the luminance values of the mask layer image should be used as the mask values.

match-source

If the mask-image property is of type <mask-source>, the luminance values of the mask layer image should be used as the mask values.

If it is of type <image>, the alpha values of the mask layer image should be used as the mask values.

Formal syntax

<a href="css/mask-mode#masking-mode"><masking-mode></a><a href="css/value_definition_syntax#hash_mark_(.23)" title="Hash mark">#</a><p>where <br><code><masking-mode> = alpha <a href="css/value_definition_syntax#single_bar" title="Single bar">|</a> luminance <a href="css/value_definition_syntax#single_bar" title="Single bar">|</a> match-source</code></p>

Description  

The mask-mode CSS property indicates whether the mask reference defined by mask-image is treated as a luminance or alpha mask.

Browser Compatibility  

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

Specifications  

License