20" height="10">
        <title>xMidYMid slice</title>
    </rect>
    <svg viewBox="0 0 100 100" width="20" height="10"
         preserveAspectRatio="xMidYMid slice" x="25" y="15">
        <use href="#smiley" />
    </svg>

    <rect x="50" y="15" width="20" height="10">
        <title>xMidYMax slice</title>
    </rect>
    <svg viewBox="0 0 100 100" width="20" height="10"
         preserveAspectRatio="xMidYMax slice" x="50" y="15">
        <use href="#smiley" />
    </svg>

    <!-- (width<height) meet --