<div class="parent">
    <img src="" class="midImg"/>
</div>

.parent{
  width: 500px;
    height: 500px;
    position: relative;
}

.parent img{
  width: 200px;
    height:200px;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%,-50%); // margin-left:-100px;margin-top:-100px;
}