Semi-transparent color masking

dabblet.css

/**
 * Semi-transparent color masking
 * (answer to question)
 */

.img-wrapper {
	position: relative;
	float:left;
	overflow: hidden;
}
.img-wrapper img{
	display:block;
}

.img-wrapper:after {
	content: '';
	position: absolute;
	top: 	15px; 
	right: 	15px; 
	bottom: 15px; 
	left:	15px;
	margin-bottom:10px;
	/*bigger than half the element is */
	border-radius:350px;
	box-shadow: 0 0 0 150px rgba(0,0,0,.7);
}

dabblet.html

<div class="img-wrapper">
	<img src="http://lorempixel.com/output/animals-q-c-350-350-6.jpg" />
</div>

settings.json

{"view":"split-vertical","fontsize":"100","seethrough":"","prefixfree":"1","page":"css"}