How to rotate element around his center?

Question

So I have an element. And I want to rotate it, using JS.

It works, but it rotates around other points.

I need to rotate it around its own center. How do I do this?

$(window).on('scroll', function() {
    var a = $(window).scrollTop();
    $('.section-4 .photo .after').css('transform', 'rotate('+ (a / 10) +'deg)');
});

Answer 1

<div class = "rotateDiv"></div>
<img src = "http://static-note-i-1.heartynote.com/img/icons/head_logo.png">
<style>
img{
transform: rotate(160deg);
}

Answer 2

使用 CSS3 特性：

transform-origin: center