JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
    <div id="opacity_div"></div>
    <img class="half_fade" src="http://i.stack.imgur.com/W7mPR.jpg?s=32&g=1">
</div>

CSS

.parent{
   position:relative;
}
#opacity_div{
   background:#fff;
   height:20px;
   width:20px;
   position:absolute;
   top:18px;
   left:6px;
   opacity:0.5 /* manipulate to desired opacity */
}
img.half_fade {
   position:absolute;
   top:0;left:0;
   z-index:-1000;
}