Simulate image "overlay" with CSS - html

Question

Basically I'm trying to simulate Photoshop's image overlay thing using images and CSS for a menu.
There are 2 versions of the menu background image: one is the normal state (pink), and one the active state (blue). The entire menu is wrapped in a DIV with the normal (pink) image as background.
How can I make it so each active menu link uses the corresponding slice of the blue image?
Like this:
My code so far
Do you think this is possible with CSS?

Answer 1

CSS Only solution for modern browsers:
ul {
background-color:#ff00ff;
background-image: -moz-radial-gradient(50% 50%, ellipse closest-side, #ffffff 0%,#ff00ff 110%);
background-image: -webkit-radial-gradient(50% 50%, ellipse closest-side, #ffffff 0%,#ff00ff 110%);
background-image: -o-radial-gradient(50% 50%, ellipse closest-side, #ffffff 0%,#ff00ff 110%);
background-image: -ms-radial-gradient(50% 50%, ellipse closest-side, #ffffff 0%,#ff00ff 110%);
background-image: radial-gradient(50% 50%, ellipse closest-side, #ffffff 0%,#ff00ff 110%);
height:50px;
width:400px;
margin:0;
padding:0;
border-radius:25px;
overflow:hidden;
}
li {
width:100px;
height:50px;
float:left;
}
li:hover {
background-color:rgba(0,0,255,0.2);
}
Click to see a working demo: http://jsfiddle.net/AlienWebguy/ZLg4B/

Answer 2

If you need to support older browsers and can't use css3, there is a number of ways to do this. One of them:
You can cut out the blue image of the entire thing (you can actually make it wider)
then
li.active {
background: url('path/to/yourImage.png') no-repeat -50px 0;
/* 50px or however wide that rounded tip is */
}
li.active.first {
background-position: left top;
}
li.active.last {
background-position: right top;
}
/* you'll need to add 'active', 'first' and 'last' classes accordingly. */

Answer 3

Are you ever going to have links at the rounded parts? If not, you could just take a pixel-wide slice of the blue image and set that to the :hover state background with repeat-x.
There are definitely other ways to do this but this is the most straightforward IMHO.
Edit: After seeing your fiddle, perhaps this isn't the case. I would consider using JavaScript to calculate appropriate x-offsets for each link, and using a slice of the overlay image in that way. Or you could just make the first link a "special case" and use a generic different-color background for the rest of the links.