Note: This repo is currently looking for maintainers: #464
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.
** We're back in business! Merged danielgindi/jquery-backstretch
, and all eyes please get back here! **
There are a couple of examples included with this package, or feel free to check it out live on the project page itself.
bower install jquery-backstretch
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"); // If your element defines a background image with CSS, you can omit the argement altogether $(".foo").backstretch(); // 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}); // Or, to load from a url that can accept a resolution and provide the best image for that resolution $(".foo").backstretch([ "path/to/image.jpg?width={width}&height={height}" ]); // Or, to automatically choose from a set of resolutions. // The width is the width of the image, and the algorithm chooses the best fit. $(".foo").backstretch([ [ { width: 1080, url: "path/to/image1_1080.jpg" }, { width: 720, url: "path/to/image1_720.jpg" }, { width: 320, url: "path/to/image1_320.jpg" } ], [ { width: 1080, url: "path/to/image2_1080.jpg" }, { width: 720, url: "path/to/image2_720.jpg" }, { width: 320, url: "path/to/image2_320.jpg" } ] ]); // If we wanted to specify different images for different pixel-ratios: $(".foo").backstretch([ [ // Will only be chosed for a @2x device { width: 1080, url: "path/to/image1_1080@2x.jpg", pixelRatio: 2 }, // Will only be chosed for a @1x device { width: 1080, url: "path/to/image1_1080.jpg", pixelRatio: 1 }, { width: 720, url: "path/to/image1_720@2x.jpg", pixelRatio: 2 }, { width: 720, url: "path/to/image1_720.jpg", pixelRatio: 1 }, { width: 320, url: "path/to/image1_320@2x.jpg", pixelRatio: 2 }, { width: 320, url: "path/to/image1_320.jpg", pixelRatio: 1 } ] ]); // If we wanted the browser to automatically choose from a set of resolutions, // While considering the pixel-ratio of the device $(".foo").backstretch([ [ // Will be chosen for a 2160 device or a 1080*2 device { width: 2160, url: "path/to/image1_2160.jpg", pixelRatio: "auto" }, // Will be chosen for a 1080 device or a 540*2 device { width: 1080, url: "path/to/image1_1080.jpg", pixelRatio: "auto" }, // Will be chosen for a 1440 device or a 720*2 device { width: 1440, url: "path/to/image1_1440.jpg", pixelRatio: "auto" }, { width: 720, url: "path/to/image1_720.jpg", pixelRatio: "auto" }, { width: 640, url: "path/to/image1_640.jpg", pixelRatio: "auto" }, { width: 320, url: "path/to/image1_320.jpg", pixelRatio: "auto" } ] ]); </script>Automatic resolution selection
The automatic resolution selection algorithm has multiple options to choose from.
The default behaviour is that it matches the logical width of the element against the specified image sizes. Which means that an element with a 320px width on a @2x device is still considered as 320px.
If you want 320px on a @2x device to be considered as 640px, then you can specify pixelRatio: "auto"
on the specific image resolution.
However if you want to limit specific images to only be chosen if the device has a certain pixel ratio - you can specify that pixel ratio i.e pixelRatio: 2.5
.
alignX
* This parameter controls the horizontal alignment of the image. Can be 'center'/'left'/'right' or any number between 0.0 and 1.0. Integer or String 0.5 alignY
* This parameter controls the vertical alignment of the image. Can be 'center'/'top'/'bottom' or any number between 0.0 and 1.0. Integer or String 0.5 scale
* Controls the scaling mode. Can be 'cover'/'fit'/'fit-smaller'/'fill' String 'cover' transition
* Type of transition to use. If multiple are specified, then it will be chosed randomly String or Array 'fade' transitionDuration
* This is the duration at which the image will transition in. Integers in milliseconds are accepted, as well as standard jQuery speed strings (slow, normal, fast). Integer or String 0 transitionEasing
* The easing function that will be used for animations. Any supported jQuery easing value jQuery default animateFirst
If true
, the first image will transition in like all the others. Boolean true fade
* Sets transition
to 'fade'
and transitionDuration
to whatever value was specified. Integer or String fadeFirst
Synonym for animateFirst
Boolean true duration
* The amount of time in between slides, when using Backstretch as a slideshow, expressed as the number of milliseconds. Integer 5000 paused
For slideshows: Disables the change between slides Boolean false start
The index of the image in the array you want to start your slideshow with. Integer 0 preload
How many images to preload at once? I.e. Lazy-loading can be enabled by specifying 0. Integer 2 preloadSize
How many images to preload in parallel? If we are preloading 5 images for the next slides, we might want to still limit it to only preload 2 or 3 at once, according to the expected available bandwidth. Integer 1 bypassCss
Avoid adding any CSS to the IMG element. I.e if you want a dynamic IMG tag that is laid out with the content. Boolean false alwaysTestWindowResolution
Always test against window's width instead of the element's width. Boolean false resolutionRefreshRate
Threshold for how long to wait before the image resolution will be switched? Integer 2500 resolutionChangeRatioThreshold
Threshold for how much should the different in the resolution be before switch image Number 0.1 (10%) centeredX
Deprecated. Still works but please do not use it. Boolean true centeredY
Deprecated. Still works but please do not use it. Boolean true
*
can be specified for individual imagesEach image in the set can be a String specifying the URL for the image, or an object with the following options, or an array of images for different resolutions to choose between. A url can be a url to a video also. Currently the plugin will automatically recognize a youtube url. If you pass urls to raw videos, you have to specify isVideo: true
.
url
The url of the image or video String alt
The alternative text for this image (If you want to play along with screen readers) String '' alignX
This parameter controls the horizontal alignment of the image. Can be 'center'/'left'/'right' or any number between 0.0 and 1.0. Integer or String 0.5 alignY
This parameter controls the vertical alignment of the image. Can be 'center'/'top'/'bottom' or any number between 0.0 and 1.0. Integer or String 0.5 scale
Controls the scaling mode. Can be 'cover'/'fit'/'fit-smaller'/'fill' String 'cover' transition
Type of transition to use. If multiple are specified, then it will be chosed randomly String or Array 'fade' transitionDuration
This is the duration at which the image will transition in. Integers in milliseconds are accepted, as well as standard jQuery speed strings (slow, normal, fast). Integer or String 0 transitionEasing
The easing function that will be used for animations. Any supported jQuery easing value jQuery default fade
Sets transition
to 'fade'
and transitionDuration
to whatever value was specified. Integer or String duration
The amount of time in between slides, when using Backstretch as a slideshow, expressed as the number of milliseconds. Integer 5000 isVideo
Tell the plugin the this is a video (if cannot be recognized automatically) Boolean false loop
Should the video be looped? If yes, then the duration will be used to determine when to stop. Boolean false mute
Should the video be muted? Boolean true poster
This is for specifying the poster
attribute in standard String Per-resolution-image definition
If you have specified an array of resolutions for a single image, then these are the available options:
Name Description Type Defaulturl
The url of the image String url
for <video>
Instead of a single url
, an array of sources can be specified. Each source has a src
and type
attributes. Array of { src, type }
alt
The alternative text for this image (If you want to play along with screen readers) String '' width
The width of the image Integer pixelRatio
A strict rule to only choose for the specified device pixel ratio. If set to 'auto', then the element's width will first be multiplied by the device's pixel ratio before evaluating. Number or "auto" undefined deviceOrientation
Restrict image selection to specific device orientation 'landscape'
or 'portrait'
undefined windowOrientation
Restrict image selection to specific window orientation (based on current window's inner width/height) 'landscape'
/ 'portrait'
/ 'square'
undefined orientation
Restrict image selection to the element's orientation based on the element's current inner width/height) 'landscape'
/ 'portrait'
/ 'square'
undefined alignX
This parameter controls the horizontal alignment of the image. Can be 'center'/'left'/'right' or any number between 0.0 and 1.0. Integer or String 0.5 alignY
This parameter controls the vertical alignment of the image. Can be 'center'/'top'/'bottom' or any number between 0.0 and 1.0. Integer or String 0.5 scale
Controls the scaling mode. Can be 'cover'/'fit'/'fit-smaller'/'fill' String 'cover' 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
'fade'
'fade_in_out'
/ 'fadeInOut'
'push_left'
/ 'pushLeft'
'push_right'
/ 'pushRight'
'push_up'
/ 'pushUp'
'push_down'
/ 'pushDown'
'cover_left'
/ 'coverLeft'
'cover_right'
/ 'coverRight'
'cover_up'
/ 'coverUp'
'cover_down'
/ 'coverDown'
loop
mode, then it will play until the end. You have to specify a duration for the specific video in order to limit its playing duration.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' ]); // Slideshow with granular control $('.foo').backstretch([ { url: 'path/to/image.jpg', duration: 3000 } { url: 'path/to/image2.jpg', fade: 250 }, { url: 'path/to/image3.jpg', alignY: 0.2 } ]); // 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. .backstretch("current")
This function returns the index of the current slide
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;
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 will also fire a "backstretch.after" event after the new images has completed loading.
$(window).on("backstretch.after", function (e, instance, index) { // Do something });
.backstretch(...)
on an already backstretched element did not properly destroy the older backstretch instance. Resulted in ghost backstretches...scale
feature.background
property, but background-image
, to allow CSS to play with colors. (@philsbury)'deviceOrientation'
, 'windowOrientation'
and 'orientation'
optionsyoutube.com
/youtu.be
domain'fade_in_out'
transitionpixelRatio == 'auto'
was ignored due to a missing rule.show(...)
call.backstretch('method', ...)
to pass all arguments, and return value.current()
function to return current slide index.background
css on the target element was sometimes cleared prematurely. (Issue #18)resolutionChangeRatioTreshold
was a typo. Changed to resolutionChangeRatioThreshold
, but keeping backwards compatibility.destroy
was not being called<video>
support!alwaysTestWindowResolution
optionresolutionRefreshRate
optionresolutionChangeRatioTreshold
optionfade
duration, the new image was still being removed asynchronously. Possibly causing a glitch if custom CSS is used.alt
image propertybypassCss
optionwidth
's meaning. width
now means the actual width of the image to match against.pixelRatio
option for multires.alignX
/alignY
/duration
/fade
on an image basiscenteredX
/centeredY
fadeFirst
featurealignX
featurealignY
featurepaused
featurestart
featurepreload
featurepreloadSize
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