Can I apply CSS(3) filters ONLY on image sections?

Question

I have a full screen background image

.bg { 
    left: 0;
    min-height: 100%; 
    min-width: 100%; 
    position: fixed; 
    top: 0; 
    z-index: -1; 
}         


        

Answer 1

http://jsfiddle.net/QvSng/6/

CSS

body {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    background: url(http://lorempixel.com/420/255) no-repeat center center fixed;
    background-size: cover;
}
body:before {
    left: 0;
    right: 0;
    margin-left:auto;
    margin-right:auto;
    content: "";
    position: absolute;
    height: 100%;
    width: 500px;
    background: url(http://lorempixel.com/420/255)  no-repeat center center fixed;
    background-size: cover;
    z-index: -1;
    filter: blur(5px);
    -webkit-filter: blur(5px);
}

div {
    height: 100%;
    width: 450px;
    margin: 0 auto;
}

Answer 2

You can actually apply blur for the before selector and inherit background-image instead of specifying url twice.

That makes the html structure more evident

JSFiddle Demo

Answer 3

To get the blur effect, use filter: blur() (with vendor prefixes). The blur applies only to the element itself, not to anything underneath it, so you'll need to reference the image within the "blur box" as well as in the background, and use background-position to control the offset so that they line up properly.

.blur {
    background-image: url('http://placekitten.com/400/400');
    background-position: center -100px;
    -webkit-filter: blur(10px);
    -moz-filter: blur(10px);
    -o-filter: blur(10px);
    -ms-filter: blur(10px);
    filter: blur(10px);
    filter: blur(10px);
}

JSFiddle Demo