Лупа на весь сайт место указателя мыши [закрыт]

function magnify(imgID, zoom) { 
  var img, glass, w, h, bw; 
  img = document.getElementById(imgID); 
  /*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 + "')"; 
  glass.style.backgroundRepeat = "no-repeat"; 
  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) + "px"; 
  } 
  function getCursorPos(e) { 
    var a, x = 0, y = 0; 
    e = e || window.event; 
    /*get the x and y positions of the image:*/ 
    a = img.getBoundingClientRect(); 
    /*calculate the cursor's x and y coordinates, relative to the image:*/ 
    x = e.pageX - a.left; 
    y = e.pageY - a.top; 
    /*consider any page scrolling:*/ 
    x = x - window.pageXOffset; 
    y = y - window.pageYOffset; 
    return {x : x, y : y}; 
  } 
} 
 
magnify("myimage", 3);

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

<h1>Image Magnifier Glass</h1> 
 
<p>Mouse over the image:</p> 
 
<div class="img-magnifier-container"> 
  <img id="myimage" src="https://www.w3schools.com/howto/img_girl.jpg" width="600" height="400"> 
</div> 
 
<p>Feel free to change the strength of the magnifier glass when initiating the magnify function.</p>