<link href='https://fonts.googleapis.com/css?family=Open+Sans' rel='stylesheet' type='text/css'>
<div class="container">
  <div class="top"></div>
  <div class="line"><p class="caption" style="font-size: 10px; top: -30px; position:relative; text-align: center; opacity: 0.5">pull me up</p></div>
  <div class="bottom"><p></p></div>
</div>
<!--<button>Position</button>-->
.html, body {
  font-family: 'Open Sans', sans-serif;
  background: black;
}

.line {
  cursor: pointer;
  position: absolute;
  width: 640px;
  height: 1px;
  background: black;
  z-index: 10;
  top: 100%;
}
.container {
  position: absolute;
  color: white;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  margin: auto; background:url('https://farm8.staticflickr.com/7475/27329811434_cd8cd9b669_b.jpg');
  background-size: 640px 360px;
  background-position: 0 -5px;
  width: 640px;
  height: 355px;
  overflow: hidden;
}

.top {
  position:absolute;
  width: 640px;
  height: 100%;
}

.bottom {
  position:absolute;
  width: 640px;
  bottom: 0px;
  height: 0px;
  overflow: hidden;
}

.top p, .bottom p {
  position: relative;
  vertical-align: middle;
}

.bottom > p {
  width: 640px;
  height: 360px;
  margin: 0px;
  position: absolute;
  bottom: 0px;
  overflow: hidden;
    background: url('https://farm8.staticflickr.com/7324/27329811284_21e47c3355_b.jpg');
  background-size: 640px 360px;
  background-position: 0 0px;
  background-repeat: no-repeat;
}
$(".line").draggable({ 
  axis: "y", 
  containment: "parent",
  drag: function() {
    $(".top").height($(".line").position().top);
    $(".bottom").height($(".container").height()-$(".top").height());
  }
});
//alert($(".line").height());
$("button").click(function() {
  var ratio = $(".top").height/$(".bottom").height+0.1;
  //alert(ratio);
});

External CSS

  1. https://ajax.googleapis.com/ajax/libs/jqueryui/1.11.2/themes/smoothness/jquery-ui.css

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js
  2. https://ajax.googleapis.com/ajax/libs/jqueryui/1.11.2/jquery-ui.min.js
  3. https://gist.githubusercontent.com/uttamg911/0892a8b7989a93b53b45432681c8019f/raw/de3c689aee67d286048a85fcb9d285faf769edd2/JQuery%2520UI%2520Touch%2520Punch%25200.2.3