<img id="bg" src="background.png";base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" alt="" style="position: fixed; left: 0; top: 0" />
#bg { position: fixed; top: 0; left: 0; }
.bgwidth { width: 100%; }
.bgheight { height: 100%; }
// JavaScript Document
(function() {
var win = $(window);
win.resize(function() {
var win_w = win.width(),
win_h = win.height(),
$bg = $("#bg");
// Load narrowest background image based on
// viewport width, but never load anything narrower
// that what's already loaded if anything.
var available = [
1024, 1280, 1366,
1400, 1680, 1920,
2560, 3840, 4860
];
var current = $bg.attr('src').match(/([0-9]+)/) ? RegExp.$1 : null;
if (!current || ((current < win_w) && (current < available[available.length - 1]))) {
var chosen = available[available.length - 1];
for (var i=0; i<available.length; i++) {
if (available[i] >= win_w) {
chosen = available[i];
break;
}
}
// Set the new image
$bg.attr('src', 'background.png' + chosen + '.png');
// for testing...
// console.log('Chosen background: ' + chosen);
}
// Determine whether width or height should be 100%
if ((win_w / win_h) < ($bg.width() / $bg.height())) {
$bg.css({height: '100%', width: 'auto'});
} else {
$bg.css({width: '100%', height: 'auto'});
}
}).resize();
})(jQuery);