JSFiddle - React, Tailwind, and code Playground

by Sascha

HTML

<html>
  <meta name="viewport" content="width=device-width, initial-scale=1.0">

  <body>
    <div class="img-magnifier-container">
      <img id="img-imgmap201293016112" src="http://upload.wikimedia.org/wikipedia/commons/thumb/9/94/Starry_Night_Over_the_Rhone.jpg/200px-Starry_Night_Over_the_Rhone.jpg" width="600" height="400">
    </div>
    <br/><br/><br/><br/>
    <div style="z-index:3">
      <button id="softtissue" type="button" onclick="softtissue();return false" class="button">
  Soft Tissue</button>
      <button id="bone" type="button" onclick="bone(); return false;" class="button">
	Bone</button>
      <button id="lung" type="button" onclick="lung()" class="button">
	Lung</button>
      <button onclick="activatemagnify()" type="button" class="button">
	Magnify</button>
    </div>
  </body>

</html>

CSS

{
  box-sizing: border-box;
}

.img-magnifier-container {
  position: relative;
}

.img-magnifier-glass {
  visibility: hidden;
  position: absolute;
  border: 3px solid #000;
  border-radius: 50%;
  cursor: none;
  /*Set the size of the magnifier glass:*/
  width: 100px;
  height: 100px;
}

JavaScript

function magnify(imgID, zoom) {
  var img, glass, w, h, bw;
  img = document.getElementById(imgID);
  var prevImgs= document.getElementsByClassName("img-magnifier-glass");
  if (prevImgs.length>0) {
    prevImgs[0].remove();
  }
  /*create magnifier glass:*/
  glass = document.createElement("DIV");
  glass.setAttribute("class", "img-magnifier-glass");
  /*insert magnifier glass:*/
  img.parentElement.insertBefore(glass, img);
  /*set background properties for the magnifier glass:*/
  glass.style.backgroundImage = "url('" + img.src + "')";
  console.log(img.src);
  glass.style.backgroundRepeat = "no-repeat";
  glass.style.visibility = "hidden";
  glass.style.backgroundSize = (img.width * zoom) + "px " + (img.height * zoom) + "px";
  bw = 3;
  w = glass.offsetWidth / 2;
  h = glass.offsetHeight / 2;
  /*execute a function when someone moves the magnifier glass over the image:*/
  glass.addEventListener("mousemove", moveMagnifier);
  img.addEventListener("mousemove", moveMagnifier);
  /*and also for touch screens:*/
  glass.addEventListener("touchmove", moveMagnifier);
  img.addEventListener("touchmove", moveMagnifier);

}

  function moveMagnifier(e) {
    var pos, x, y;
    /*prevent any other actions that may occur when moving over the image*/
    e.preventDefault();
    /*get the cursor's x and y positions:*/
    pos = getCursorPos(e);
    x = pos.x;
    y = pos.y;
    /*prevent the magnifier glass from being positioned outside the image:*/
    if (x > img.width - (w / zoom)) {
      x = img.width - (w / zoom);
    }
    if (x < w / zoom) {
      x = w / zoom;
    }
    if (y > img.height - (h / zoom)) {
      y = img.height - (h / zoom);
    }
    if (y < h / zoom) {
      y = h / zoom;
    }
    /*set the position of the magnifier glass:*/
    glass.style.left = (x - w) + "px";
    glass.style.top = (y - h) + "px";
    /*display what the magnifier glass "sees":*/
    glass.style.backgroundPosition = "-" + ((x * zoom) - w + bw) + "px -" + ((y * zoom) - h + bw)...