function magnify(imgID, zoom, backgroundImageUrl = "") {
    var img, glass, w, h, bw;

    /* Get img element by id or use passed in element */
    if (isNaN(imgID)) {
        img = imgID;
    } else {
        img = document.getElementById(imgID);
    }

    /* Create magnifier glass: */
    glass = document.createElement("DIV");
    glass.setAttribute("id", "glass");
    glass.setAttribute("class", "img-magnifier-glass");
    /* Insert magnifier glass: */
    if (img.parentElement.getElementsByClassName('img-magnifier-glass').length == 0)
        img.parentElement.insertBefore(glass, img);

    /* Set background properties for the magnifier glass: */
    if (backgroundImageUrl == "") {
        /* Remove thumbnail size restrictions for clearer image  */
        glass.style.backgroundImage = "url('" + img.src.replace("&h=200&w=200", "") + "')";
    } else {
        glass.style.backgroundImage = backgroundImageUrl;
    }
    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, horizontalOffset, verticalOffset;
        /* 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);
        horizontalOffset = (img.parentElement.clientWidth - img.clientWidth) / 2;
        verticalOffset = (img.parentElement.clientHeight - img.clientHeight) / 2;
        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 };
    }
}

function stopMagnify() {
    var elements = document.getElementsByClassName('img-magnifier-glass');
    while (elements.length > 0)
        elements[0].parentNode.removeChild(elements[0]);
};