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Parallax Effect Adjustment for individual DIVs

I created a parallax effect, as it was described here:
Is there a way to make parallax work within a DIV
This method works pretty well, but I have a problem with it. My page is basically composed of alternating DIVs. White DIVs with text and DIVs with a picture in it, which moves with the parallax effect. This works pretty well, unless, that I have to manually adjust the position of each picture DIV. Here is the code from the header:
<script type="text/javascript">
$(window).scroll(function () {
parallax();
});
function parallax() {
var ev = {
scrollTop: document.body.scrollTop || document.documentElement.scrollTop
};
ev.ratioScrolled = ev.scrollTop / (document.body.scrollHeight - document.documentElement.clientHeight);
render(ev);
}
function render(ev) {
var t = ev.scrollTop;
var y = Math.round(t * 2/3) - 100;
$('#ff-section01').css('background-position', 'center ' + y + 'px');
$('#ff-section03').css('background-position', 'center ' + (y - 1000) + 'px');
$('#ff-section05').css('background-position', 'center ' + (y - 1700) + 'px');
$('#ff-section07').css('background-position', 'center ' + (y - 2750) + 'px');
}
</script>
As you can see, each section got another vertical position in the background-position value at the bottom. 0, 1000, 1700, 2750. This works well so far, but as soon as the intermediate Text DIVs change in height, this method doesn't work, as the value is always calculated from the top of the page. The HTML of one section looks like this:
<div class="ff-section03" id="ff-section03"></div>
So very simple, and combined with the CSS:
.ff-section03 {
width: 100%; height: 550px;
position: relative;
background: url('system/urbansolutions.jpg') center -300px no-repeat;
}
Also very simple. What can I do, that the calculations are not dependent of the page height? I basically don't want to subtract a superficial number from the background-position, so that the parallax effect works, not dependent of the location on the website.
Thanks a lot!
Sebastian

jQuery ScrollTop..."disable" when hit bottom of screen

Trying to implement a parallax scroll (got two separate elements) #slides and #body, the #body will overlay the #slides when you scroll down the page (parallax effect)
Problem arises when you scroll right to the bottom of the page, it appears to jump...think it is looking at the height.
here is the code.
<script>
$(window).scroll(function () {
var n1 = ($(this).scrollTop() / 0.2)+'px';
$('#slides').css({ 'top': 0-($(this).scrollTop() / 0.9) + "px"});
console.log(n1);
$('#body').css({ 'margin-top': 0-($(this).scrollTop() / 0.45) + "px"});
});
$(window).scroll(function () {
if ($(window).scrollTop() + $(window).height() > $(document).height() - 100) {
alert("bottom!");
}
});
</script>
I am wanting to create a jquery function to "disable" this slide when it hits the footer HTML tag? any ideas how to write this. I have done an "alert" so this fires when you scroll down...but wanting to transfer this into "disbaling" jQuery scroll

Fixed this now, this can be removed

JS change height and return to original CSS height

Hoping to get some help on some javascript i'm getting stuck with.
Q1: JS RETURN TO IMAGE HEIGHT AND MARGIN
My layout is horizontal scroll of smaller images positioned in a grid, using different height percentages and margins to position.
When you click on any of the images they all expand to height:100% and margin:0 which clears all previous styles putting it into a simple large image layout.
My question is how do I add a function that when clicking on .image-container the height and margins returns to how it was originally set in the css
JS FIDDLE DEMO (click any center image)
// GALLERY 100% height
$('.image-container').click(function(){
$('.image-container img').animate({'height': '100%'},900)
.animate({'margin': '0'},900);
});
// ? REMOVE HEIGHT ?
$('.image-container').click(function(){
$('.image-container img').animate({'height': '?'},900)
.animate({'margin': '?'},900);
});
EDIT UPDATED QUESTION: Q2 HOW TO MAKE PAGE SIZE GROW WITH LARGER IMAGES
Right now my .image-container is set to a large width but with responsive images it's hard to find the correct width, is there a way to find this width and to make it grow along with the click grow of images (displayed above)
.image-container {
display:block;
width:3600px;
height: 75%;
float:left;
position:absolute;
top: 13%;
left: 120px;
z-index: -1;
}
Thanks for any help!

You need to store the original height in a variable.
Check out the updated fiddle
var originalheight;
// GALLERY 100% height
$('.image-container').click(function(){
originalheight = $('.image-container img').height();
$('.image-container img').animate({'height': '100%'},900)
.animate({'margin': '0'},900);
});
//REMOVE HEIGHT ?
$('.image-container').click(function(){
$('.image-container img').animate({'height': originalheight},900)
.animate({'margin': '0'},900);
});
EDIT:
Sorry about the goof up in previous solution. I didn't notice I was using click twice unnecessarily.
Here's the updated solution with the updated fiddle.
var originalheight;
$('.image-container').click(function () {
if (!originalheight) originalheight = $('.image-container img').height();
if ($('.image-container img').css('height') == originalheight + "px") { // GALLERY 100% height
$('.image-container img').animate({
'height': '100%'
}, 900).animate({
'margin': '0'
}, 900);
} else { //REMOVE HEIGHT ?
$('.image-container img').animate({
'height': originalheight
}, 900).animate({
'margin': '0'
}, 900);
}
});

This is my idea, hope it'll work:
// Before animation
var heights = new Array();
var margins = new Array();
$('.image-container img').each(function(){
heights.push($(this).css('height'));
});
$('.image-container img').each(function(){
margins.push($(this).css('margin'));
});
//
$('.image-container').click(function(){
$('.image-container img').animate({'height': '100%'},900)
.animate({'margin': '0'},900);
});
// ? REMOVE HEIGHT ?
$('.image-container').click(function(){
$('.image-container img').animate({'height': heights[$(this).index()]},900)
.animate({'margin': margins[$(this).index()]},900);
});

First of all, I suggest you to use the focusout and blur event to undo changes, because the way you implement your 'click' event, the second part only will be considered (you erase the first click implementation doing so). the best thing, is to enlarge the image when clicked, and reinit it's size when you click away.
Try this :
// GALLERY 100% height
$('.image-container')
.bind('click', function(){
$('.image-container img').animate({height: '100%'},900)
.animate({margin: 0},900);
})
.bind('focusout blur', function(){
$('.image-container img').animate({height: ''},900)
.animate({margin: ''},900);
});
Or better, use classes in which you define the behaiviors on clicking, and on clicking again, for exemple :
<style>
.clickimage{ height : 100%; margin :0;}
.yourOriginalValues {height : original; margin : original;}
</style>
$('.yourOriginalValues').click(function(){
$(this).switchClass( "yourOriginalValues", "clickimage", 900 );
});
$('.clickimage).click(function(){
$(this).switchClass( "clickimage", "yourOriginalValues", 900 );
});
ps. the switchClass method, is a jQuery UI functionality.

Use jQuery to detect when an element is near the bottom of the page

I've got a script that works out the distance of a list of elements from the top of the page, but I am unsure how to detect it's distance from the bottom. When it hits the bottom (well, 20px before the bottom) I want to fire an event and fade it out:
$(window).on('load resize scroll', function () {
$('.links__item').each(function () {
if (($(this).offset().top - $(window).scrollTop()) < 20) {
$(this).stop().fadeTo(100, 0)
} else {
$(this).stop().fadeTo('fast', 1)
}
})
})
If anyone has any advice, much appreciated. I'm looping through the elements to detect it, so when one of them hits 20px from the bottom, I want to fade it out. Thanks!

You can use the jQuery function height() at your calculations, like:
$(window).height();
$(this).height();
Specifically, if you want to detect if the top of the element is near to the bottom of the page, you can use this calc:
if ( $(this).offset().top > ($(window).scrollTop() + $(window).height() - 20) ) // True

Halcyon,
I am not sure what you want to fire but you can test the bottom of the page like this
$(window).on('load resize scroll', function () {
$('.links__item').each(function () {
if( ($(this).offset().top > ($(window).scrollTop() + $(window).height() - 20)) {
$(this).stop().fadeTo(100, 0)
} else {
$(this).stop().fadeTo('fast', 1)
}
})
})
Reason being is jQuery finds bottom of the page based upon its height
1 $(window).height(); // returns height of browser viewport
2 $(document).height(); // returns height of HTML document

Scroll to the center of viewport

I would like to center a div by clicking it. So if I'm clicking a div I want it to scroll to the center of the browser viewport. I don't want to use anchor points like the guides and examples I've seen. How can I achieve this?

In some way you have to identify the clickable elements. I build an example, that uses the class-attribute for that.
Step 1
This is the script, that does the work:
$('html,body').animate({
scrollTop: $(this).offset().top - ( $(window).height() - $(this).outerHeight(true) ) / 2
}, 200);
What you tried is to scroll the container to the top of the page. You also have to calculate and subtract the difference between the container height and the viewport height. Divide this by two (as you want to have the same space on top and bottom and you are ready to go.
Step 2
Then you add the click handler to all the elements:
$(document).ready(function () {
$('.image').click( function() {
$('html,body').animate({ scrollTop: $(this).offset().top - ( $(window).height() - $(this).outerHeight(true) ) / 2 }, 200);
});
});
Step 3
Set up some HTML/CSS:
<style>
div.image {
border: 1px solid red;
height: 500px;
width: 500px;
}
</style>
<div class="image">1</div>
<div class="image">2</div>
<div class="image">3</div>
<div class="image">4</div>
<div class="image">5</div>
And you're done.
Check out the demo
Try it yourself http://jsfiddle.net/insertusernamehere/3T9Py/

HTMLElement.prototype.scrollToCenter = function(){
window.scrollBy(0, this.getBoundingClientRect().top - (window.innerHeight>>1));
}
Achieved with pure JavaScript for Scrolling to Center in the vertical direction. And it's similar in the horizontal direction.
I don't take elements' height into consideration, because they maybe larger than the height of screen.

I know this question is old, but right now, you can use scrollIntoView:
For example:
document.body.scrollIntoView({
behavior: 'smooth',
inline: 'center',
block: 'center'
});

I've got one slight modification to offer.
If the "adjustment factor" i.e. ( $(window).height() - $(this).outerHeight(true) ) / 2 is < 0 you can get undesirable results whereby you overshoot that element in the viewport with your scroll.
I added a max(0,adjustment factor) to correct :
function scrollIntoView(el) {
var offsetTop = $j(el).offset().top;
var adjustment = Math.max(0,( $j(window).height() - $j(el).outerHeight(true) ) / 2);
var scrollTop = offsetTop - adjustment;
$j('html,body').animate({
scrollTop: scrollTop
}, 200);
}