HOW TO

How To Create an Image Zoom

Learn how to create an image zoom

Image Zoom

Mouse over the image:

Zoom Preview:

function imageZoom(imgID, resultID) { var img, lens, result, cx, cy; img = document.getElementById(imgID); lens = document.createElement("DIV"); lens.setAttribute("class", "img-zoom-lens"); img.parentElement.insertBefore(lens, img); result = document.getElementById(resultID); cx = result.offsetWidth / lens.offsetWidth; cy = result.offsetHeight / lens.offsetHeight; result.style.backgroundImage = "url('" + img.src + "')"; result.style.backgroundSize = (img.width * cx) + "px " + (img.height * cy) + "px"; lens.addEventListener("mousemove", moveLens); img.addEventListener("mousemove", moveLens); lens.addEventListener("touchmove", moveLens); img.addEventListener("touchmove", moveLens); function moveLens(e) { var pos, x, y; e.preventDefault(); pos = getCursorPos(e); x = pos.x - (lens.offsetWidth / 2); y = pos.y - (lens.offsetHeight / 2); if (x > img.width - lens.offsetWidth) {x = img.width - lens.offsetWidth;} if (x < 0) {x = 0;} if (y > img.height - lens.offsetHeight) {y = img.height - lens.offsetHeight;} if (y < 0) {y = 0;} lens.style.left = x + "px"; lens.style.top = y + "px"; result.style.backgroundPosition = "-" + (x * cx) + "px -" + (y * cy) + "px"; } function getCursorPos(e) { var a, x = 0, y = 0; e = e || window.event; a = img.getBoundingClientRect(); x = e.pageX - a.left - window.pageXOffset; y = e.pageY - a.top - window.pageYOffset; return {x : x, y : y}; } } imageZoom("zoomimage", "zoomresult");

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Create an Image Zoom

Step 1) Add HTML:

Example

<div class="img-zoom-container">
<img id="myimage" src="img_girl.jpg" width="300" height="240" alt="Girl">
<div id="myresult" class="img-zoom-result"></div>
</div>

Step 2) Add CSS:

The container must have a "relative" positioning.

Example

* {box-sizing: border-box;}

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

.img-zoom-lens {
position: absolute;
border: 1px solid #d4d4d4;
/*set the size of the lens:*/
width: 40px;
height: 40px;
}

.img-zoom-result {
border: 1px solid #d4d4d4;
/*set the size of the result div:*/
width: 300px;
height: 300px;
}

Step 3) Add JavaScript:

Example

function imageZoom(imgID, resultID) {
var img, lens, result, cx, cy;
img = document.getElementById(imgID);
result = document.getElementById(resultID);
/* Create lens: */
lens = document.createElement("DIV");
lens.setAttribute("class", "img-zoom-lens");
/* Insert lens: */
img.parentElement.insertBefore(lens, img);
/* Calculate the ratio between result DIV and lens: */
cx = result.offsetWidth / lens.offsetWidth;
cy = result.offsetHeight / lens.offsetHeight;
/* Set background properties for the result DIV */
result.style.backgroundImage = "url('" + img.src + "')";
result.style.backgroundSize = (img.width * cx) + "px " + (img.height * cy) + "px";
/* Execute a function when someone moves the cursor over the image, or the lens: */
lens.addEventListener("mousemove", moveLens);
img.addEventListener("mousemove", moveLens);
/* And also for touch screens: */
lens.addEventListener("touchmove", moveLens);
img.addEventListener("touchmove", moveLens);
function moveLens(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);
    /* Calculate the position of the lens: */
    x = pos.x - (lens.offsetWidth / 2);
    y = pos.y - (lens.offsetHeight / 2);
    /* Prevent the lens from being positioned outside the image: */
    if (x > img.width - lens.offsetWidth) {x = img.width - lens.offsetWidth;}
    if (x < 0) {x = 0;}
    if (y > img.height - lens.offsetHeight) {y = img.height - lens.offsetHeight;}
    if (y < 0) {y = 0;}
    /* Set the position of the lens: */
    lens.style.left = x + "px";
    lens.style.top = y + "px";
    /* Display what the lens "sees": */
    result.style.backgroundPosition = "-" + (x * cx) + "px -" + (y * cy) + "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};
}
}

Step 4) Initiate the Zoom Effect:

Example

<script>
imageZoom("myimage", "myresult");
</script>

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