Elastic Image Slideshow with Thumbnail Preview

Today we want to show you how to create a simple elastic slideshow with a thumbnail preview. The slideshow will adjust automatically to its surrounding container and we can navigate through the slides by using the thumbnail previewer or the autoplay slideshow option.

To make this slideshow responsive, we will use a mixture of JavaScript and CSS techniques.

The fabulous photography used in the demo is by Bartek Lurka and it is licensed under the Attribution-NonCommercial-NoDerivs 3.0 Unported License.

So, let’s do it!

The Markup

We will create two unordered lists, one for the main slider and one for the thumbnail navigation beneath the large image. The “large slider” list elements will contain the image and a title with an h2 and h3 element:

<div id="ei-slider" class="ei-slider">
	<ul class="ei-slider-large">
		<li>
			<img src="images/large/1.jpg" alt="image01" />
			<div class="ei-title">
				<h2>Creative</h2>
				<h3>Geek</h3>
			</div>
		</li>
		<li>...</li>
	</ul>
	<ul class="ei-slider-thumbs">
		<li class="ei-slider-element">Current</li>
		<li>
			<a href="#">Slide 1</a>
			<img src="images/thumbs/1.jpg" alt="thumb01" />
		</li>
		<li>...</li>
	</ul>
</div>

The list for the thumbnail preview navigation will contain an absolute element (the first list element with the class ei-slider-element and the thumbnail list elements which consist of an anchor and an image (the thumbnail).

Now, let’s add the style.

The CSS

First, we will define the style for the main wrapper. We will have the slider inside of a wrapper which will be 100% in width in order to stretch over the whole window. Now, the slider itself will also have a width of 100%, making it use all the space there is in width. But we will also define a maximum width, so that the images in our slider don’t get stretched too much when dealing with a big screen:

.ei-slider{
	position: relative;
	width: 100%;
	max-width: 1920px;
	height: 400px;
	margin: 0 auto;
}

While the images are loading, we will add a loading element which will have the following style:

.ei-slider-loading{
	width: 100%;
	height: 100%;
	position: absolute;
	top: 0px;
	left: 0px;
	z-index:999;
	background: rgba(0,0,0,0.9);
	color: #fff;
	text-align: center;
	line-height: 400px;
}

The unordered list will occupy all the space we defined and will not show any overflow:

.ei-slider-large{
	height: 100%;
	width: 100%;
	position:relative;
	overflow: hidden;
}

The list elements that will hold the images will be of absolute position. Depending from where we navigate we will slide them from the left or from the right:

.ei-slider-large li{
	position: absolute;
	top: 0px;
	left: 0px;
	overflow: hidden;
	height: 100%;
	width: 100%;
}

The width of the image will be set in our JavaScript but we also want to define it if we don’t have JS enabled:

.ei-slider-large li img{
	width: 100%;
}

The title holder will be positioned in the middle of the list element with a right margin to fit the picture in our example (and not to overlap the face in the photography):

.ei-title{
	position: absolute;
	right: 50%;
	margin-right: 13%;
	top: 30%;
}

The style for the headings is the following:

.ei-title h2, .ei-title h3{
	text-align: right;
}
.ei-title h2{
	font-size: 40px;
	line-height: 50px;
	font-family: 'Playfair Display', serif;
	font-style: italic;
	color: #b5b5b5;
}
.ei-title h3{
	font-size: 70px;
	line-height: 70px;
	font-family: 'Open Sans Condensed', sans-serif;
	text-transform: uppercase;
	color: #000;
}

The navigation list will have a small height of 13 pixels. We will set a default width for the thumbnails in the initialisation of our plugin. From that width we will set a max-width to the unordered list. This will make it elastic when we resize the window, but not occupy all the width there is.

.ei-slider-thumbs{
	height: 13px;
	margin: 0 auto;
	position: relative;
}

The list elements of the navigation list will be of relative position:

.ei-slider-thumbs li{
	position: relative;
	float: left;
	height: 100%;
}

The special slider element that indicates the current image will be positioned absolutely on top of the current thumbnail element:

.ei-slider-thumbs li.ei-slider-element{
	top: 0px;
	left: 0px;
	position: absolute;
	height: 100%;
	z-index: 10;
	text-indent: -9000px;
	background: rgba(0,0,0,0.9);
}

The link elements will have a white box shadow to show a tiny separation and some darker shadow to appear under them. We’ll also add a transition to the element so that we can change the background-color smoothly on hover:

.ei-slider-thumbs li a{
	display: block;
	text-indent: -9000px;
	background: #666;
	width: 100%;
	height: 100%;
	cursor: pointer;
	box-shadow: 
        0px 1px 1px 0px rgba(0,0,0,0.3), 
        0px 1px 0px 1px rgba(255,255,255,0.5);
    transition: background 0.2s ease;
}
.ei-slider-thumbs li a:hover{
	background-color: #f0f0f0;
}

The image will be positioned absolutely and we will add a transition and a box reflection to it. Adding a max-width to it will make sure that the thumb will adjust to the size of the list element when the window gets smaller than the width of the unordered list itself:

.ei-slider-thumbs li img{
	position: absolute;
	bottom: 50px;
	opacity: 0;
	z-index: 999;
	max-width: 100%;
    transition: all 0.4s ease;
	-webkit-box-reflect: 
        below 0px -webkit-gradient(
            linear, 
            left top, 
            left bottom, 
            from(transparent), 
            color-stop(50%, transparent), 
            to(rgba(255,255,255,0.3))
            );
}

On hover, we will animate the opacity and the bottom value so that it appears to be sliding in from the top:

.ei-slider-thumbs li:hover img{
	opacity: 1;
	bottom: 13px;
}

Last but not least, we want to make sure that from a certain width on, the slider title will not cover the best parts of our image. So, we will make it appear at the bottom of the image with a semi-transparent white background:

@media screen and (max-width: 830px) {
	.ei-title{
		position: absolute;
		right: 0px;
		margin-right: 0px;
		width: 100%;
		text-align: center;
		top: auto;
		bottom: 10px;
		background: rgba(255,255,255,0.9);
		padding: 5px 0;
	}
	.ei-title h2, .ei-title h3{
		text-align: center;
	}
	.ei-title h2{
		font-size: 20px;
		line-height: 24px;
	}
	.ei-title h3{
		font-size: 30px;
		line-height: 40px;
	}
}

For the case that we don’t have JavaScript enabled we will add this piece of CSS to ensure that our slides are shown. We will hide the thumbnail navigation:

.ei-slider{
	height: auto;
}
.ei-slider-thumbs{
	display: none;
}
.ei-slider-large li{
	position: relative;
}

And that’s all the style! Let’s take a look at the JavaScript.

The JavaScript

Since we are creating a plugin, let’s first look at the definition of the options:

$.Slideshow.defaults 		= {
	// animation types:
	// "sides" : new slides will slide in from left / right
	// "center": new slides will appear in the center
	animation			: 'sides', // sides || center
	// if true the slider will automatically 
	// slide, and it will only stop if the user 
	// clicks on a thumb
	autoplay			: false,
	// interval for the slideshow
	slideshow_interval	: 3000,
	// speed for the sliding animation
	speed			: 800,
	// easing for the sliding animation
	easing			: '',
	// percentage of speed for the titles animation. 
	// Speed will be speed * titlesFactor
	titlesFactor		: 0.60,
	// titles animation speed
	titlespeed			: 800,
	// titles animation easing
	titleeasing			: '',
	// maximum width for the thumbs in pixels
	thumbMaxWidth		: 150
};

In the _init funtion we will start by setting the opacity of the title elements and the images to 0. We will also preload the images and once they are loaded we will set their size and position according to the slider width and height. Then we configure the thumbnails navigation by setting the width of the unordered list and the list items.

We will then show the first slide and if we set autoplay in our options to true, then we’ll start the slideshow. The we initialize the events which are the events for resizing the window and for clicking the thumbnails:

_init 				: function( options ) {
			
	this.options 		= $.extend( true, {}, $.Slideshow.defaults, options );
	
	// set the opacity of the title elements and the image items
	this.$imgItems.css( 'opacity', 0 );
	this.$imgItems.find('div.ei-title > *').css( 'opacity', 0 );
	
	// index of current visible slider
	this.current		= 0;
	
	var _self			= this;
	
	// preload images
	// add loading status
	this.$loading		= $('
Loading
').prependTo( _self.$el );
	
	$.when( this._preloadImages() ).done( function() {
		
		// hide loading status
		_self.$loading.hide();
		
		// calculate size and position for each image
		_self._setImagesSize();
		
		// configure thumbs container
		_self._initThumbs();
		
		// show first
		_self.$imgItems.eq( _self.current ).css({
			'opacity' 	: 1,
			'z-index'	: 10
		}).show().find('div.ei-title > *').css( 'opacity', 1 );
		
		// if autoplay is true
		if( _self.options.autoplay ) {
		
			_self._startSlideshow();
		
		}
		
		// initialize the events
		_self._initEvents();
	
	});
	
},

And here are the single functions we just talked about:

_preloadImages		: function() {
	
	// preloads all the large images
	
	var _self	= this,
		loaded	= 0;
	
	return $.Deferred(
	
		function(dfd) {
	
			_self.$images.each( function( i ) {
				
				$('').load( function() {
				
					if( ++loaded === _self.itemsCount ) {
					
						dfd.resolve();
						
					}
				
				}).attr( 'src', $(this).attr('src') );
			
			});
			
		}
		
	).promise();
	
},
_setImagesSize		: function() {
	
	// save ei-slider's width
	this.elWidth	= this.$el.width();
	
	var _self	= this;
	
	this.$images.each( function( i ) {
		
		var $img	= $(this);
			imgDim	= _self._getImageDim( $img.attr('src') );
			
		$img.css({
			width		: imgDim.width,
			height		: imgDim.height,
			marginLeft	: imgDim.left,
			marginTop	: imgDim.top
		});
		
	});

},
_getImageDim		: function( src ) {
	
	var $img    = new Image();
					
	$img.src    = src;
			
	var c_w		= this.elWidth,
		c_h		= this.$el.height(),
		r_w		= c_h / c_w,
		
		i_w		= $img.width,
		i_h		= $img.height,
		r_i		= i_h / i_w,
		new_w, new_h, new_left, new_top;
			
	if( r_w > r_i ) {
		
		new_h	= c_h;
		new_w	= c_h / r_i;
	
	}
	else {
	
		new_h	= c_w * r_i;
		new_w	= c_w;
	
	}
			
	return {
		width	: new_w,
		height	: new_h,
		left	: ( c_w - new_w ) / 2,
		top		: ( c_h - new_h ) / 2
	};

},
_initThumbs			: function() {

	// set the max-width of the slider elements to the one set in the plugin's options
	// also, the width of each slider element will be 100% / total number of elements
	this.$sliderElems.css({
		'max-width' : this.options.thumbMaxWidth + 'px',
		'width'		: 100 / this.itemsCount + '%'
	});
	
	// set the max-width of the slider and show it
	this.$sliderthumbs.css( 'max-width', this.options.thumbMaxWidth * this.itemsCount + 'px' ).show();
	
},
_startSlideshow		: function() {

	var _self	= this;
	
	this.slideshow	= setTimeout( function() {
		
		var pos;
		
		( _self.current === _self.itemsCount - 1 ) ? pos = 0 : pos = _self.current + 1;
		
		_self._slideTo( pos );
		
		if( _self.options.autoplay ) {
		
			_self._startSlideshow();
		
		}
	
	}, this.options.slideshow_interval);

},

The _slideTo function will take care of the transition between the slides. Depending on what we’ve set in our options, we’ll either make the new slide appear from the side or simply make it fade in without sliding it. We’ll also take care of the title and its heading elements which we will slightly slide from the sides by setting their right margins. The thumbnail slider element will have to move to the new corresponding thumbnail position.

_slideTo			: function( pos ) {
	
	// return if clicking the same element or if currently animating
	if( pos === this.current || this.isAnimating )
		return false;
	
	this.isAnimating	= true;
	
	var $currentSlide	= this.$imgItems.eq( this.current ),
		$nextSlide		= this.$imgItems.eq( pos ),
		_self			= this,
		
		preCSS			= {zIndex	: 10},
		animCSS			= {opacity	: 1};
	
	// new slide will slide in from left or right side
	if( this.options.animation === 'sides' ) {
		
		preCSS.left		= ( pos > this.current ) ? -1 * this.elWidth : this.elWidth;
		animCSS.left	= 0;
	
	}	
	
	// titles animation
	$nextSlide.find('div.ei-title > h2')
			  .css( 'margin-right', 50 + 'px' )
			  .stop()
			  .delay( this.options.speed * this.options.titlesFactor )
			  .animate({ marginRight : 0 + 'px', opacity : 1 }, this.options.titlespeed, this.options.titleeasing )
			  .end()
			  .find('div.ei-title > h3')
			  .css( 'margin-right', -50 + 'px' )
			  .stop()
			  .delay( this.options.speed * this.options.titlesFactor )
			  .animate({ marginRight : 0 + 'px', opacity : 1 }, this.options.titlespeed, this.options.titleeasing )
	
	$.when(
		
		// fade out current titles
		$currentSlide.css( 'z-index' , 1 ).find('div.ei-title > *').stop().fadeOut( this.options.speed / 2, function() {
			// reset style
			$(this).show().css( 'opacity', 0 );	
		}),
		
		// animate next slide in
		$nextSlide.css( preCSS ).stop().animate( animCSS, this.options.speed, this.options.easing ),
		
		// "sliding div" moves to new position
		this.$sliderElem.stop().animate({
			left	: this.$thumbs.eq( pos ).position().left
		}, this.options.speed )
		
	).done( function() {
		
		// reset values
			$currentSlide.css( 'opacity' , 0 ).find('div.ei-title > *').css( 'opacity', 0 );
			$nextSlide.css( 'z-index', 1 );
			_self.current	= pos;
			_self.isAnimating		= false;
		
		});
		
},

The _initEvents function will recalculate the sizes of the images when we resize the window and reposition the thumbnail slider element. When clicking on a thumbnail we will show the regarding slide:

_initEvents			: function() {
	
	var _self	= this;
	
	// window resize
	$(window).on( 'smartresize.eislideshow', function( event ) {
		
		// resize the images
		_self._setImagesSize();
	
		// reset position of thumbs sliding div
		_self.$sliderElem.css( 'left', _self.$thumbs.eq( _self.current ).position().left );
	
	});
	
	// click the thumbs
	this.$thumbs.on( 'click.eislideshow', function( event ) {
		
		if( _self.options.autoplay ) {
		
			clearTimeout( _self.slideshow );
			_self.options.autoplay	= false;
		
		}
		
		var $thumb	= $(this),
			idx		= $thumb.index() - 1; // exclude sliding div
			
		_self._slideTo( idx );
		
		return false;
	
	});
	
}

And that’s it! I hope you enjoyed this tutorial and find it useful!