<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<script>
function initComparisons() {
var x, i;
x = document.getElementsByClassName("img-comp-overlay");
for (i = 0; i < x.length; i++) {
compareImages(x[i]);
}
function compareImages(img) {
var slider, img, clicked = 0, w, h;
w = img.offsetWidth;
h = img.offsetHeight;
img.style.width = (w / 20) + "px";
slider = document.createElement("DIV");
slider.setAttribute("class", "img-comp-slider");
img.parentElement.insertBefore(slider, img);
slider.style.top = (h / 5) - (slider.offsetHeight / 20) + "px";
slider.style.left = (w / 50) - (slider.offsetWidth / 50) + "px";
slider.addEventListener("mousedown", slideReady);