How to fade in background image by CSS3 Animation

Question

I am making a menu that each item has a text like item1, item2 and etc. in hover the background colour changes, text becomes transparent and a background image replaces. I used this code to ease in and out the style. but it only works for background colour and not the image.

#nav li:hover {
    color:transparent !important;
    text-shadow: none;
    background-color: rgba(255, 0, 0, .5);

    -webkit-transition: all 1s ease-in;
    -moz-transition: all 1s ease-in;
    -o-transition: all 1s ease-in;
    -ms-transition: all 1s ease-in;
    transition: all 1s ease-in;
}

Here is the online version: http://jsfiddle.net/q4uHz/

Answer 1

Background images cannot be animated; there would be no algorithm for that. A simple solution is to include <img> with the icon in your HTML instead with opacity: 0 and animate that. Something like.

<li id="home">
<img src="http://cdn3.iconfinder.com/data/icons/picons-social/57/16-apple-48.png">
<a href="#home">Home</a></li>

#nav li {
    position: relative;
}
#nav li img {
    opacity: 0;
    position: absolute;
    transition: all 1s ease-in;
    top: 0;
    left: 0;
}
#nav li:hover img {
    opacity: 1;
}

Full example on this snippet:

#nav {
    font: 14px 'LeagueGothicRegular', Arial, sans-serif;
    color: #f9f8cc;
    width:300px;
    clear: both;
    height: 58px;
    margin: 5px 0px 0px 50px;
    background:#c2c2c2;
    opacity:.8;
}

#nav ul {
    margin: 0;
    padding: 0;
}
#nav li {
    list-style-type: none;
    background-image: none;
    color: #FDE99D;
    float: left;
    height:48px; width:85px;
    border-right:1px #333333 solid;
    text-align:center;
    padding-top:10px;
    position: relative;
    
    -webkit-transition: all 1s ease-out;
    -moz-transition: all 1s ease-out;
    -o-transition: all 1s ease-out;
    -ms-transition: all 1s ease-out;
    transition: all 1s ease-out;
}

#nav li a {
    color: #000;
    text-shadow: 0px 2px 2px #222;
    text-transform: uppercase;
}

#nav li:hover a {
    color: #999;
    color:transparent !important;
    text-shadow: none;
    
}

#nav li:hover {
    color:transparent !important;
    text-shadow: none;
    background-color: rgba(255, 0, 0, .5);
    
    -webkit-transition: all 1s ease-in;
    -moz-transition: all 1s ease-in;
    -o-transition: all 1s ease-in;
    -ms-transition: all 1s ease-in;
    transition: all 1s ease-in;
}
#nav li img {
    opacity: 0;
    position: absolute;
    transition: all 1s ease-in;
    top: 0;
    left: 0;
}
#nav li:hover img {
    opacity: 1;
}

<div id="nav">
    <ul>
     <li id="home">
         <img src="http://cdn3.iconfinder.com/data/icons/picons-social/57/16-apple-48.png">
         <a href="#home">Home</a></li>
     <li id="item1">
         <img src="http://cdn3.iconfinder.com/data/icons/picons-social/57/16-apple-48.png">
         <a href="#contact">Contact</a></li>
      
    </ul>
  </div>