jQuery on window scroll animate background image position

Question

I am trying to achieve a scrolling effect using jQuery. I have a background div set to 100% browser window size with overflow hidden. This has a large background image that

Answer 1

If you don't want to be hassled with the extra background div, here's my code I wrapped up from several examples:

$(window).scroll(function () {
    setBackgroundPosition();
})
$(window).resize(function() {
    setBackgroundPosition();
});
function setBackgroundPosition(){
    $("body").css('background-position', "-" + (1920 - $(window).width()) / 2 + "px " + -(Math.max(document.body.scrollTop, document.documentElement.scrollTop) / 4) + "px");
}

The Math.max is required for cross-browser issues. Also replace '1920' with the width of your background image

body{
    background-image:url(images/background.jpg);
    background-position:center top;
    background-repeat:no-repeat;
    background-attachment:fixed;
}

Answer 2

Here you go. Background is set to 10% scroll. You can change the background scroll rate by changing the 10 in the code.

CSS

html, body{
    height:100%;
    min-height:100%;
    margin:0;
    padding:0;
}
.bg{
    width:100%;
    height:100%;
    background: #fff url(..) no-repeat fixed 0 0;
    overflow:auto;
}

<div class="bg">
   <span>..</span>
</div>

JavaScript

$('.bg').scroll(function() {
    var x = $(this).scrollTop();
    $(this).css('background-position', '0% ' + parseInt(-x / 10) + 'px');
});

Check working example at http://jsfiddle.net/Vbtts/
Click this link for the full screen example: http://jsfiddle.net/Vbtts/embedded/result/

---

Answer 3

This worked for me:

In js:

$(window).scroll(function() {
    var x = $(this).scrollTop();
    $('#main').css('background-position', '100% ' + parseInt(-x / 1) + 'px' + ', 0% ' + parseInt(-x / 2) + 'px, center top');
});

In css:

#main {
background: url(../img/img1.png) center top no-repeat, url(../img/img2.png) center top no-repeat, url(../img/img3.png);
background-repeat: no-repeat, no-repeat, repeat-x;
background-position: right top, left top, center top;

Where #main is the div whose background image I wanted to move. No need to have height: 100% for html, body.

This is a variation for multiple background images.

Answer 4

Look here to see an example of how far the user has scrolled on the page. See the $(this).scrollTop()?

Rather than referencing $(this), try using the background div. Then use a .scroll function to determine how much to move the background.

Your code should look something sort of like this:

$("html").scroll(function{
  var move["bottom"] = $("bg_div").scrollTop();
  $("bg_div").animate({bottom: move}, 500);
});

Answer 5

I don't think you can use += or -= when you have two parts in the CSS. There is something you can do, it is a bit tricky but it works:

$(window).scroll(function(){
    if($(this).scrollTop() > 200) {
        var bgpos = $("#div").css("background-position");
        var bgposInt = 0;
        if(bgpos.indexOf("px")!=-1) {
            bgpos = bgpos.substr(bgpos.indexOf("px")+3);
            bgposInt = parseInt(bgpos.substr(0, bgpos.indexOf("px")));
        }
        bgposInt += 10;
        $("#div").animate({"background-position": "0 "+bgposInt+"px"}, 500);
    }
});

This code gets only the second number from the background-position of the div (the top position), converts it to int, and increases it by 10. Then it just animates the div to the new position.

Answer 6

This might do it:

$(window).scroll(function(){
    $('#div').css("background-position",parseInt($(this).scrollTop()*0.05));
})