Backstretch

Backstretch is a simple jQuery plugin that allows you to add a dynamically-resized, slideshow-capable background image to any page or element. The image will stretch to fit the page/element, and will automatically resize as the window/element size changes.

Demo

There are a couple of examples included with this package, or feel free to check it out live on the project page itself.

Setup

Include the jQuery library (version 1.7 or newer) and Backstretch plugin files in your webpage (preferably at the bottom of the page, before the closing BODY tag):

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script src="jquery.backstretch.min.js"></script>
<script>
  // To attach Backstrech as the body's background
  $.backstretch("path/to/image.jpg");

  // You may also attach Backstretch to a block-level element
  $(".foo").backstretch("path/to/image.jpg");

  // Or, to start a slideshow, just pass in an array of images
  $(".foo").backstretch([
    "path/to/image.jpg",
    "path/to/image2.jpg",
    "path/to/image3.jpg"
  ], {duration: 4000});
</script>

Options

Name	Description	Type	Default
centeredX	The ratio of the width/height of the image doesn't always jive with the width/height of the window. This parameter controls whether or not we center the image on the X axis to account for the discrepancy.	Boolean	true
centeredY	This parameter controls whether or not we center the image on the Y axis to account for the aforementioned discrepancy.	Boolean	true
fade	This is the speed at which the image will fade in. Integers in milliseconds are accepted, as well as standard jQuery speed strings (slow, normal, fast).	Integer or String	0
duration	The amount of time in between slides, when using Backstretch as a slideshow, expressed as the number of milliseconds.	Integer	5000
bleed	The amount by which to bleed the wrapper off the containing element. Helps overcome pixel gaps caused by rounding errors with percentage-based elements. Note: this only works when using Backstretch on an element (not the body), and will add overflow: hidden to the containing element.	Number	0
parallax	Adds a parallax effect to block-level backstretch elements	Boolean	false

Slideshow API

Once you've instantiated a Backstretch slideshow, there are many actions that you can perform it:

// Start a slideshow
$('.foo').backstretch([
  'path/to/image.jpg',
  'path/to/image2.jpg',
  'path/to/image3.jpg'
]);

// Pause the slideshow
$('.foo').backstretch("pause");

// Advance to the next slide
$('.foo').backstretch("next");

Method	Description
.backstretch("show", n)	Jump to the slide at a given index, where n is the number of the image that you'd like to display. Slide number starts at 0.
.backstretch("prev")	Display the previous image in a slideshow.
.backstretch("next")	Advance to the next image in a slideshow.
.backstretch("pause")	Pause the slideshow.
.backstretch("resume")	Resume a paused slideshow.
.backstretch("destroy", preserveBackground)	Destroy the Backstretch instance. Optionally, you can pass in a Boolean parameter, preserveBackground, to determine whether or not you'd like to keep the current image stretched as the background image.
.backstretch("resize")	This method is called automatically when the container (window or block-level element) is resized, however you can always call this manually if needed.

Public Variables

Sometimes, you'll want to access Backstretch's images after you've instantiated the plugin. For example, perhaps you'd like to be able add more images to a slideshow. Doing so is easy. You can access the images array as follows:

$('.foo').backstretch([
  'path/to/image.jpg',
  'path/to/image2.jpg',
  'path/to/image3.jpg'
]);

// Access the instance
var instance = $('.foo').data('backstretch');

// Then, you can manipulate the images array directly
instance.images.push('path/to/image4.jpg')

Additionally, the current index of a slideshow is available through the instance as well:

$("body").data("backstretch").index;

Events

backstretch.before

Backstretch will fire a "backstretch.before" event before a new image loads, triggering a function that is passed the event, Backstretch instance, and index of the image that will be displayed. If you listen for that event, you can, for example, coordinate other changes to coincide with your slideshow.

$(window).on("backstretch.before", function (e, instance, index) {
  // If we wanted to stop the slideshow after it reached the end
  if (index === instance.images.length - 1) {
    instance.pause();
  };
});

backstretch.after

Backstretch will also fire a "backstretch.after" event after the new images has completed loading.

$(window).on("backstretch.after", function (e, instance, index) {
  // Do something
});

Changelog

Version 2.1

• Added "parallax" option to give block-level backstretch elements a parallax effect
• Added "bleed" option to bleed background image outside of it's container

Version 2.0

• Now accepts an array of images to create a slideshow
• Can attach Backstretch to any block-level element, not just the body
• Deprecated "speed" option in favor of "fade" for fadeIn timing
• Added "duration" option, and Slideshow API

Version 1.2

• You can now called backstretch twice, and it will replace the existing image.

Version 1.1

• Added 'centeredX' and 'centeredY' options.
• Removed 'hideUntilReady' option. It looks pretty bad if you don't hide the image until it's fully loaded.
• Fixed IE img onload bug.
• Now supports iPhone/iPad orientation changes.