<!doctype html>
<title>CSS test reference</title>
<style>
* {
margin: 0;
padding: 0;
box-sizing: border-box;
}
html, body {
width: 100%;
height: 100%;
}
body {
padding: 20px;
position: relative;
}
.parent {
border: 3px solid green;
position: absolute;
height: 60vh;
}
.parent img {
height: calc(60vh - 6px);
}
</style>
<div class="parent">
<img src="/images/blue96x96.png">
</div>