background-sizeに相当するものはありますか：画像要素をカバーして含みますか？

body {
  margin: 0;
}
img {
  display: block;
  width: 100vw;
  height: 100vh;
  object-fit: cover;
}

<img src="http://lorempixel.com/1500/1000" />

body {
  margin: 0;
}
img {
  position: fixed;
  width: 0;
  height: 0;
  padding: 50vh 50vw;
  background: url(http://lorempixel.com/1500/1000/city/Dummy-Text) no-repeat;
  background-size: cover;
}

<img src="http://placehold.it/1500x1000" />

.container {
  position: relative;
  overflow: hidden;
  /* Width and height can be anything. */
  width: 50vw;
  height: 50vh;
}

img {
  position: absolute;
  /* Position the image in the middle of its container. */
  top: -9999px;
  right: -9999px;
  bottom: -9999px;
  left: -9999px;
  margin: auto;
  /* The following values determine the exact image behaviour. */
  /* You can simulate background-size: cover/contain/etc.
     by changing between min/max/standard width/height values.
     These values simulate background-size: cover
  */
  min-width: 100%;
  min-height: 100%;
}

<div class="container">
    <img src="http://placehold.it/200x200" alt="" />
</div>

.container {
  width: 800px;
  height: 300px;
  border: 1px solid black;
  overflow:hidden;
  position:relative;
}
.container.contain img {
  position: absolute;
  left:-10000%; right: -10000%; 
  top: -10000%; bottom: -10000%;
  margin: auto auto;
  max-width: 10%;
  max-height: 10%;
  -webkit-transform:scale(10);
  transform: scale(10);
}
.container.cover img {
  position: absolute;
  left:-10000%; right: -10000%; 
  top: -10000%; bottom: -10000%;
  margin: auto auto;
  min-width: 1000%;
  min-height: 1000%;
  -webkit-transform:scale(0.1);
  transform: scale(0.1);
}

<h1>contain</h1>
  <div class="container contain">
    <img 
       src="https://www.google.de/logos/doodles/2014/european-parliament-election-2014-day-4-5483168891142144-hp.jpg" 
       />
    <!-- 366x200 -->
  </div>
  <h1>cover</h1>
  <div class="container cover">
    <img 
       src="https://www.google.de/logos/doodles/2014/european-parliament-election-2014-day-4-5483168891142144-hp.jpg" 
       />
    <!-- 366x200 -->
  </div>

.img-container {
  position: relative;
  overflow: hidden;
}

.background-image {
  position: absolute;
  min-width: 1000%;
  min-height: 1000%;
  left: 50%;
  top: 50%;
  transform: translateX(-50%) translateY(-50%) scale(0.1);
  z-index: -1;
}

<div class="img-container">
  <img class="background-image" src="https://picsum.photos/1024/768/?random">
  <p style="padding: 20px; color: white; text-shadow: 0 0 10px black">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
  </p>
</div>

.img-container {
  position: relative;
  overflow: hidden;
  z-index: 0;
}

.background-image {
  position: absolute;
  max-width: 10%;
  max-height: 10%;
  left: 50%;
  top: 50%;
  transform: translateX(-50%) translateY(-50%) scale(10);
  z-index: -1;
}

<div style="background-color: black">
  <div class="img-container">
    <img class="background-image" src="https://picsum.photos/1024/768/?random">
    <p style="padding: 20px; color: white; text-shadow: 0 0 10px black">
      Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
    </p>
  </div>
</div>

.image-container {
  height: 200px;
  width: 200px;
  overflow: hidden;
  background-color: rebeccapurple;
  border: 1px solid yellow;
  position: relative;
}

.image {
  max-height: 100%;
  max-width: 100%;
  margin: auto;
  position: absolute;
  transform: translate(-50%, -50%);
  top: 50%;
  left: 50%;
}

<!-- wide -->
<div class="image-container">
  <img class="image" src="http://placehold.it/300x100">
</div>

<!-- tall -->
<div class="image-container">
  <img class="image" src="http://placehold.it/100x300">
</div>

.img-ctr{
  background: red;/*visible only in contain mode*/
  border: 1px solid black;
  height: 300px;
  width: 600px;
  overflow: hidden;
  position: relative;
  display: block;
}
.img{
  display: block;

  /*contain:*/
  /*max-height: 100%;
  max-width: 100%;*/
  /*--*/

  /*cover (not work for images wider and shorter than the container):*/
  min-height: 100%;
  width: 100%;
  /*--*/

  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

<p>Large square:
<span class="img-ctr"><img class="img" src="http://placehold.it/1000x1000"></span>
</p>
<p>Small square:
<span class="img-ctr"><img class="img" src="http://placehold.it/100x100"></span>
</p>
<p>Large landscape:
<span class="img-ctr"><img class="img" src="http://placehold.it/2000x1000"></span>
</p>
<p>Small landscape:
<span class="img-ctr"><img class="img" src="http://placehold.it/200x100"></span>
</p>
<p>Large portrait:
<span class="img-ctr"><img class="img" src="http://placehold.it/1000x2000"></span>
</p>
<p>Small portrait:
<span class="img-ctr"><img class="img" src="http://placehold.it/100x200"></span>
</p>
<p>Ultra thin portrait:
<span class="img-ctr"><img class="img" src="http://placehold.it/200x1000"></span>
</p>
<p>Ultra wide landscape (images wider and shorter than the container):
<span class="img-ctr"><img class="img" src="http://placehold.it/1000x200"></span>
</p>

.tall-img{
    margin-top:-50%;
    width:100%;
}
.wide-img{
    margin-left:-50%;
    height:100%;
}

.wide-img{
    margin-left:-42%;
    height:100%;
}
.tall-img{
    margin-top:-42%;
    width:100%;
}