How to add a thumbnail image/photo gallery

For those who would like to show pictures in an image gallery, here's a gallery made with JavaScript and CSS that includes some thumbnails with which you will be able to pick different images on mouse click.

With the help of CSS, we can then place the <img> element to make it appear at the same position for each thumb and we'll be able to style the thumbnails as small blocks with a defined height/width. The script will add a click-event for each <li> object that changes it's child's <img> visibility and assigns an "active" class name to the <li>.

How to Add Image Gallery with Thumbnails to Blogger

Step 1. Log in to your Blogger dashboard, go to Template > Edit HTML

Step 2. Click anywhere inside the code area and press the CTRL + F keys to open the Blogger search box

Step 3. Inside the search box type </head> and hit enter to find it.

Step 4. Now pick one of the styles below that you like the most, then copy the code associated with it:

Style 1

<style type='text/css'>
#image-gallery {display: none;}
  #jquery-gallery {padding:0;margin:0;list-style: none; width: 500px;}
  #jquery-gallery li {width:84px; height: 80px;background-size: 100%;-webkit-background-size: cover;-moz-background-size: cover; -o-background-size: cover;background-size: cover;margin-right: 10px; border: 3px solid #fff; outline: 1px solid #E3E3E3; margin-bottom: 10px;opacity: .5; filter:alpha(opacity=50); float: left; display: block; }
#jquery-gallery li img { position: absolute; top: 100px; left: 0px; display: none;}
  #jquery-gallery li.active img { display: block; border: 3px solid #fff; outline: 1px solid #E3E3E3; width:490px; max-height: 375px;}
  #jquery-gallery li.active, #jquery-gallery li:hover { outline-color: #DFDFDF; opacity: .99;filter:alpha(opacity=99);}
</style>

Style 2

<style type='text/css'>
#image-gallery { display: none; }
#jquery-gallery {padding:0;margin:0;list-style: none; width: 200px; }
#jquery-gallery li {background-size: 100%;-webkit-background-size: cover;-moz-background-size: cover; -o-background-size: cover;background-size: cover;margin-right: 10px; width: 80px; height: 80px; border: 3px solid #fff; outline: 1px solid #ddd; margin-right: 10px; margin-bottom: 10px; opacity: .5;filter:alpha(opacity=50); float: left; display: block; }
#jquery-gallery li img { position: absolute; top: 0px; left: 200px; display: none; }
#jquery-gallery li.active img { display: block; width:370px; border: 3px solid #fff; outline: 1px solid #E3E3E3; }
#jquery-gallery li.active, #jquery-gallery li:hover { outline-color: #bbb; opacity: .99;filter:alpha(opacity=99);}
</style>

Note: The display: none; of the first ID (#image-gallery) is to prevent images appear with their actual size before they go inside the gallery container, this is while loading the code. In #jquery-gallery we have the width of the container for the thumbnails (200px), so that they display in two rows and for this we need to count the width of the thumbnail (80px) plus the margins between them. The left declaration of #jquery-gallery li img is to move the larger thumbnail that shows on mouse click so that it won't overlap with the smaller thumbnails.

Step 5. Paste the code that you copied earlier just above the </head> tag.

Step 6. Just above the same </head> tag, add this script:

<script type='text/javascript'>
//<![CDATA[
var gal = {
init : function() {
if (!document.getElementById || !document.createElement || !document.appendChild) return false;
if (document.getElementById('image-gallery')) document.getElementById('image-gallery').id = 'jquery-gallery';
var li = document.getElementById('jquery-gallery').getElementsByTagName('li');
li[0].className = 'active';
for (i=0; i<li.length; i++) {
li[i].style.backgroundImage = 'url(' + li[i].getElementsByTagName('img')[0].src + ')';
li[i].title = li[i].getElementsByTagName('img')[0].alt;
gal.addEvent(li[i],'click',function() {
var im = document.getElementById('jquery-gallery').getElementsByTagName('li');
for (j=0; j<im.length; j++) {
im[j].className = '';
}
this.className = 'active';
});
}
},
addEvent : function(obj, type, fn) {
if (obj.addEventListener) {
obj.addEventListener(type, fn, false);
}
else if (obj.attachEvent) {
obj["e"+type+fn] = fn;
obj[type+fn] = function() { obj["e"+type+fn]( window.event ); }
obj.attachEvent("on"+type, obj[type+fn]);
}
}
}
gal.addEvent(window,'load', function() {
gal.init();
});
//]]>
</script>

Basically what this script does is to look if there is any ID named "image-gallery" and get the different list items that may exist within it. These elements will be displayed as thumbnails and a function will decide what to do when they are clicked. So, each time we click on a thumbnail, the "active" class will be assigned and the thumbnail should be visible in a larger container.

Step 7. Save the changes by clicking on the Save template button.

And finally, here's the HTML code. This is a normal list with the image-gallery ID, enclosed within a DIV with a relative position to avoid side effects of other pre-existing positions.

Step 8. Paste the below HTML to where you want to display the gallery by going either to Layout and adding a new gadget (click on the Add a gadget link and choose HTML/JavaScript), or inside a post or page within the HTML section.

<div style="position:relative;">
<ul id="image-gallery">
<li><img src="IMAGE-URL1" /></li>
<li><img src="IMAGE-URL2" /></li>
<li><img src="IMAGE-URL3" /></li>
<li><img src="IMAGE-URL4" /></li>
<li><img src="IMAGE-URL5" /></li>
</ul>
</div>

Note: if elements on your page overlap with this gallery, you might need to add the height declaration after the position: relative; The value of height depends on the size of your gallery.

Example:

<div style="position:relative; height: 500px;"> 

Change IMAGE-URL1 with the image URL. If you don't know how to get the address of an image, see this
In case you need to add links to your images, add this HTML structure instead:

<div style="position:relative;">
<ul id="image-gallery">
<li><a href="page-URL"><img src="IMAGE-URL1" /></a></li>
<li><a href="page-URL"><img src="IMAGE-URL2" /></a></li>
<li><a href="page-URL"><img src="IMAGE-URL3" /></a></li>
<li><a href="page-URL"><img src="IMAGE-URL4" /></a></li>
<li><a href="page-URL"><img src="IMAGE-URL5" /></a></li>
</ul>
</div>

Again, here you need to replace the page-URL text with the URL of your page/post.

Save your widget or page and you're done!