image 안쪽의 border 값 주기 : MASK

<div class="image-container">
	<img />
</div>

.image-container {
	position: relative;
	
	&:before {
		content: '';
    display: block;
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    border: 1px solid #000;
    opacity: 0.1;
	}
}