var images = [
    {width:1260, center:630,  margin: 20, src:'index_data/bg.jpg'},
    {width:3407, center:1793, margin: 60, src:'index_data/bg2.jpg'}
];

function reposition() {
    var width = window.innerWidth;
    var img = images[0];

    for (var idx in images) {
        img = images[idx];

        if (img.width > window.innerWidth) {
            break;
        }
    }

    var offset = (width / 2) - img.center;

    var content   = document.getElementById('content');
    var title     = document.getElementById('title');
    var intro     = document.getElementById('introtext');
    var blog      = document.getElementById('blog');
    var copyright = document.getElementById('copyright');

    content.style.backgroundImage = 'url(' + img.src + ')';
    content.style.backgroundPosition = offset + 'px 0px';

    intro.style.paddingLeft = (offset > 0 ? offset : 0) +'px';
    title.style.paddingLeft = (offset > 0 ? offset : 0) + 'px';
    blog.style.paddingLeft = ((width / 2) + img.margin) + 'px';
}

window.onload = reposition;
window.onresize = reposition;