CSS を使用して画像またはビデオ上にアイコンを配置する方法

<code class="css">.container {
  position: relative;
}

.container img {
  display: block;
}

.container .fa-download {
  position: absolute;
  bottom: 0;
  left: 0;
}</code>

<code class="html"><link href="https://use.fontawesome.com/releases/v5.7.1/css/all.css" rel="stylesheet"/>

<div class="container">
  <img src="https://placekitten.com/300/300">
  <a href="dog.png" download="new-filename"><i class="fas fa-download"></i></a>
</div></code>

<code class="css">.container {
  position: relative;
}

.container img {
  display: block;
}

.container .btn-download {
  position: absolute;
  bottom: 0;
  left: 0;
  padding: 6px;
  background-color: #337ab7;
  color: #fff;
  border: none;
  border-radius: 3px;
}

.container .btn-download i {
  font-size: 1.5em;
}</code>

<code class="html"><link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<link href="https://use.fontawesome.com/releases/v5.7.1/css/all.css" rel="stylesheet"/>

<div class="container">
  <img src="https://placekitten.com/300/300">
  <a href="dog.png" download="new-filename" class="btn-download"><i class="fas fa-download"></i></a>
</div></code>