CSS Masking

.dotted-border {
  border: dotted;
  position: relative;
  width: 390px;
  height: 400px;
}

#top-left,
#middle,
#bottom-right {
  position: absolute;
  top: 0;
}

#top-left {
  left: 400px;
  clip: rect(0, 130px, 90px, 0);
}

#middle {
  left: 270px;
  clip: rect(100px, 260px, 190px, 130px);
}

#bottom-right {
  left: 140px;
  clip: rect(200px, 390px, 290px, 260px);
}

<p class="dotted-border">
  <img src="macarons.png" alt="Original graphic" />
  <img id="top-left" src="macarons.png" alt="Graphic clipped to upper left" />
  <img id="middle" src="macarons.png" alt="Graphic clipped towards middle" />
  <img
    id="bottom-right"
    src="macarons.png"
    alt="Graphic clipped to bottom right" />
</p>

section {
  align-items: flex-start;
}

.example-container {
  text-align: left;
  padding: 20px;
}

#example-element {
  float: left;
  width: 150px;
  margin: 20px;
}

<section class="default-example" id="default-example">
  <div class="example-container">
    <img
      class="transition-all"
      id="example-element"
      src="https://developer.mozilla.org/shared-assets/images/examples/balloon-small.jpg"
      width="150" />
    We had agreed, my companion and I, that I should call for him at his house,
    after dinner, not later than eleven o'clock. This athletic young Frenchman
    belongs to a small set of Parisian sportsmen, who have taken up "ballooning"
    as a pastime. After having exhausted all the sensations that are to be found
    in ordinary sports, even those of "automobiling" at a breakneck speed, the
    members of the "Aéro Club" now seek in the air, where they indulge in all
    kinds of daring feats, the nerve-racking excitement that they have ceased to
    find on earth.
  </div>
</section>

body {
  display: flex;
  gap: 20px;
}
svg {
  width: 110px;
  height: 110px;
}

#star1 path {
  clip-rule: evenodd;
}

#star2 path {
  clip-rule: nonzero;
}

#star3 path {
  fill: none;
  stroke: black;
  stroke-width: 1;
}

<svg>
  <clipPath id="star1">
    <path d="M50,0 21,90 98,35 2,35 79,90z" />
  </clipPath>
  <rect clip-path="url(#star1)" width="95" height="95" />
</svg>

<svg>
  <clipPath id="star2">
    <path d="M50,0 21,90 98,35 2,35 79,90z" />
  </clipPath>
  <rect clip-path="url(#star2)" width="95" height="95" />
</svg>

<svg id="star3">
  <path d="M50,0 21,90 98,35 2,35 79,90z" />
</svg>

img,
div {
  border: 20px dashed rebeccapurple;
  box-sizing: content-box;
  padding: 20px;
  height: 220px;
  width: 220px;
}

img {
  mask: repeating-radial-gradient(
      circle,
      transparent 0 5px,
      lightgreen 15px 20px
    )
    content-box border-box 0% 0% / 100px 100px repeat;
}

div {
  background: repeating-radial-gradient(
      circle,
      transparent 0 5px,
      lightgreen 15px 20px
    )
    content-box border-box 0% 0% / 100px 100px repeat;
}

<img
  src="https://mdn.github.io/shared-assets/images/examples/progress-pride-flag.jpg"
  alt="Pride flag" />
<div></div>

.masked {
  width: 200px;
  background-color: lavender;
  border: 18px solid salmon;
  padding: 10px;

  -webkit-mask-box-image: url("https://mdn.github.io/shared-assets/images/examples/mask-border-diamonds.png")
    30 fill /          /* slice */
    20px /             /* width */
    1px                /* outset */
    round;             /* repeat */

  mask-border:
    url("https://mdn.github.io/shared-assets/images/examples/mask-border-diamonds.png")
    30 fill /        /* slice */
    20px /           /* width */
    1px              /* outset */
    round;           /* repeat */
}

<div class="masked">
  This element is surrounded by a bitmap-based mask border! Pretty neat, isn't
  it?
</div>

div {
  width: 100px;
  height: 100px;
  background-color: #8cffa0;
  margin: 10px;
  border: 20px solid #8ca0ff;
  padding: 20px;
  mask-image: url("https://mdn.github.io/shared-assets/images/examples/mdn.svg");
  mask-size: 100% 100%;
}
.content-box {
  mask-clip: content-box;
}
.border-box {
  mask-clip: border-box;
}
.padding-box {
  mask-clip: padding-box;
}
div::before {
  content: attr(class);
  position: relative;
  top: -10px;
}

body {
  display: flex;
  flex-flow: row wrap;
}

<div class="border-box"></div>
<div class="padding-box"></div>
<div class="content-box"></div>

div {
  width: 100px;
  height: 100px;
  background-color: red;

  mask-image:
    url("https://mdn.github.io/shared-assets/images/examples/mdn.svg"),
    url("https://mdn.github.io/shared-assets/images/examples/mask-star.svg");
  mask-size: 100% 100%;

  mask-composite: subtract;
}

<div></div>

img {
  mask-image: radial-gradient(black 50%, transparent 60%);
}

<img
  src="https://mdn.github.io/shared-assets/images/examples/progress-pride-flag.jpg"
  alt="Pride flag" />

div {
  background: blue linear-gradient(red, blue);
  mask-image: url("https://mdn.github.io/shared-assets/images/examples/mdn.svg");
}

.alpha {
  mask-mode: alpha;
}

.luminance {
  mask-mode: luminance;
}

.matchSource {
  mask-mode: match-source;
}

div {
  width: 227px;
  height: 200px;
  float: left;
  text-align: center;
  line-height: 65px;
  color: white;
  text-shadow: 1px 1px 2px black;
  font-family: sans-serif;
}

<div class="alpha">ALPHA</div>
<div class="luminance">LUMINANCE</div>
<div class="matchSource">MATCH-SOURCE</div>

div {
  width: 100px;
  height: 100px;
  margin: 10px;
  border: 10px solid blue;
  background-color: #8cffa0;
  padding: 10px;
  mask-image: url("https://mdn.github.io/shared-assets/images/examples/mask-star.svg");
}
section {
  border: 1px solid black;
}

.content div {
  mask-origin: content-box;
}

.padding div {
  mask-origin: padding-box;
}

.border div {
  mask-origin: border-box;
}

.comparison div {
  mask-image: none;
}

section::before {
  content: attr(class);
  display: block;
  text-align: center;
}

body {
  display: flex;
  flex-flow: row wrap;
  gap: 10px;
}

<section class="content">
  <div></div>
</section>
<section class="padding">
  <div></div>
</section>
<section class="border">
  <div></div>
</section>
<section class="comparison">
  <div></div>
</section>

section {
  border: 1px solid black;
  width: 250px;
  height: 250px;
}

div {
  width: 250px;
  height: 250px;
  margin-bottom: 10px;
  background: blue linear-gradient(red, blue);

  mask-image: url("https://developer.mozilla.org/shared-assets/images/examples/mask-star.svg");
  mask-repeat: no-repeat;
  mask-position: top right;
}

<section>
  <div></div>
</section>

div {
  width: 250px;
  height: 250px;
  background-image: linear-gradient(red, blue);

  mask-image: url("https://developer.mozilla.org/shared-assets/images/examples/mask-star.svg");
  mask-size: 100px 100px;

  mask-repeat: round space;
}

<div></div>

div {
  width: 200px;
  height: 400px;
  background: blue linear-gradient(red, blue);
  mask-image: url("https://developer.mozilla.org/shared-assets/images/examples/mdn.svg");
}

.width {
  mask-size: 50%;
}

.height {
  mask-size: auto 50%;
}

body {
  display: flex;
  gap: 20px;
}

<div class="width"></div>
<div class="height"></div>

mask#alphaMask {
  mask-type: alpha;
}

mask#luminanceMask {
  mask-type: luminance;
}

img.alphaMaskType {
  mask-image: url("#alphaMask");
}

img.luminanceMaskType {
  mask-image: url("#luminanceMask");
}

<img
  class="alphaMaskType"
  src="https://mdn.github.io/shared-assets/images/examples/progress-pride-flag.jpg"
  alt="Pride flag" />
<img
  class="luminanceMaskType"
  src="https://mdn.github.io/shared-assets/images/examples/progress-pride-flag.jpg"
  alt="Pride flag" />

<svg height="0" width="0">
  <mask id="alphaMask">
    <path
      d="M20,70 A40,40,0,0,1,100,70 A40,40,0,0,1,180,70 Q180,130,100,190 Q20,130,20,70 Z"
      fill="green"
      stroke="white"
      stroke-width="20" />
    <circle
      cx="170"
      cy="170"
      r="40"
      fill="rgb(0 0 0 / 0.5)"
      stroke="rgb(255 255 255 / 0.5)"
      stroke-width="20" />
  </mask>
  <mask id="luminanceMask">
    <path
      d="M20,70 A40,40,0,0,1,100,70 A40,40,0,0,1,180,70 Q180,130,100,190 Q20,130,20,70 Z"
      fill="green"
      stroke="white"
      stroke-width="20" />
    <circle
      cx="170"
      cy="170"
      r="40"
      fill="rgb(0 0 0 / 0.5)"
      stroke="rgb(255 255 255 / 0.5)"
      stroke-width="20" />
  </mask>
</svg>