<script>
if (window.internals) {
    // Force software rendering mode.
    window.internals.settings.setAcceleratedCompositingEnabled(false);
}
</script>
<style>
img {
    margin: 15px;
}
</style>
<img style="filter: drop-shadow(0 0 0 black)" src="resources/reference.png">
<img style="filter: drop-shadow(5px 5px 2px black)" src="resources/reference.png">
<img style="filter: drop-shadow(5px 5px 0px red)" src="resources/reference.png">
<img style="filter: drop-shadow(10px 10px 0px red)" src="resources/reference.png">
<img style="filter: drop-shadow(5px 5px 10px blue)" src="resources/reference.png">