A green rect with a hole in the middle, with soft edges.
<svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<radialGradient id="rg">
<stop offset="0" stop-color="black"/>
<stop offset="1" stop-color="white"/>
</radialGradient>
<mask id="myMask">
<rect x="0" y="0" width="100" height="100" fill="white"/>
<circle cx="50" cy="50" r="45" fill="url(#rg)"/>
</mask>
<image xlink:href="https://cdn.pixabay.com/photo/2013/04/06/05/06/ship-100978_960_720.jpg" width="100" height="100"/>
<rect x="0" y="0" width="100" height="100" fill="green" mask="url(#myMask)"/>
</svg>