.container {
width:100%;
height:100%;
background:grey;
background-position: 0% 50%;
}
<div class="container">
<svg width="100%" height="100%" viewBox="0 0 400 300" preserveAspectRatio="none">
<defs>
<clipPath id="clip" clipPathUnits="objectBoundingBox">
<polygon points="0,1 0,0.5 0.5,0.67 1,0.5 1,1"/>
</clipPath>
</defs>
<image href="http://placeimg.com/400/300/any" clip-path="url(#clip)" width="100%" height="100%"/>
</svg>
</div>