[JSWolf]

This is the code I use for a full screen image.

HTML:

<div class="cover">
<img alt="" class="cover" src="../images/9781101543535_cover.jpg"/>
</div>

CSS:

body {
  widows: 1;
  orphans: 1;
  margin-top: 0;
  margin-right: 0;
  margin-bottom: 0;
  margin-left: 0;
  text-align: justify;
}
img {
  max-height: 100%;
  max-width: 100%;
}
.cover {
  text-align: center;
  text-indent: 0;
  height: 100%;
}