Sudo Overlay mode HTML so srcset can be used.

img_overlay_mock.html

<div class="image-wrapper">
  <div class="image-container">
    <img src="https://www.tyndellphotographic.com/assets/images/products-large/8844cf7c81c27a17ab0d721d38b4aeff.jpg" alt="Sample image">
  </div>
</div>

<style type="text/css">
.image-wrapper {
  background-color: #fff;
  height: 500px;
  width: 500px;
  border:1px solid red;
}

.image-container {
  text-align: center;
  line-height: 500px;
  height: 100%;
}

.image-container img {
  max-width: 100%;
  max-height: 100%;
  width: auto;
  height: auto;
  vertical-align: middle;
}
</style>