Image scrolling on hover

Question

I want to make an image inside div to scroll down on hover. And that part is working.

Also, I need to make that it scroll longer if the image is longer and because of that I was trying to use calc inside of transition, but it is not working.

Here is my code:

.preview {
  position: relative;
  width: 75%;
  height: 90vh;
  overflow: hidden;
  border: 1px solid red;
  background-color: transparent;
}

.previewimg {
  width: 100%;
  height: 100%;
  top: 0;
  background-image: url(https://www.n2odesigns.com/wp-
 content/uploads/Projema-Website-Preview-2016.jpg);
  background-repeat: no-repeat;
  background-size: 100% auto;
  background-position-y: 0;
  transition: all calc(0.02s * height) ease-in-out;
}

.previewimg:hover {
  background-position-y: 100%;
  height: 100%;
  transition: all calc(0.02s * height) ease-in-out;
}

<div class="preview">
  <div class="previewimg"></div>
</div>

If there is some other better way to do this I can use it too.

Answer 1

Ok to do this you need it to be an image only not a background image, to do this transition duration based on height functionality, please use the below code.

$('.previewimg').css("transition", "transform " + 0.02 * $('.previewimg').height() + "s ease");

.preview {
  position: relative;
  width: 75%;
  height: 300px;
  overflow: hidden;
  border: 1px solid red;
  background-color: transparent;
}

.preview .previewimg {
  width: 100%;
  height: auto;
  transform: translateY(0px); 
}

.preview:hover .previewimg {
  transform: translateY(calc(-100% + 300px)); 
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="preview">
  <img class="previewimg" src="https://www.n2odesigns.com/wp-content/uploads/Projema-Website-Preview-2016.jpg"/>
</div>

Answer 2

If you are accepting JS as a solution then here is a code you can add without changing your HTML/CSS structure :

function getHeight(url) {
  console.log(url);
  var img = new Image();
  img.src = url;
  return 0.002*parseInt(img.height);
}
var e =$(".previewimg");
var tr = "all "+getHeight(e.css("background-image").replace(/^url\(['"](.+)['"]\)/, '$1'))+"s ease-in-out";
console.log(tr);
e.css('transition',tr);

.preview {
  position: relative;
  width: 75%;
  height: 90vh;
  overflow: hidden;
  border: 1px solid red;
  background-color: transparent;
}

.previewimg {
  width: 100%;
  height: 100%;
  top: 0;
  background-image: url(https://www.n2odesigns.com/wp-content/uploads/Projema-Website-Preview-2016.jpg);
  background-repeat: no-repeat;
  background-size: 100% auto;
  background-position-y: 0;
}

.previewimg:hover {
  background-position-y: 100%;
  height: 100%;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="preview">
  <div class="previewimg"></div>
</div>