var bgDiv = '#bg_image';
var bgImg = '#bg_image img';

$(function() {	
	// Initial resizing
	resizeBgImage();
	
	$(window).bind('resize', function() {
		resizeBgImage();
	});
		
});


function resizeBgImage() {
	// Define original width and height of the image
    var imgWidth = $(bgImg).attr('width');
    var imgHeight = $(bgImg).attr('height');
    
    // Define image ratio
    var ratio = imgHeight/imgWidth;
    
    // Get browser dimensions
    var winWidth = $(window).width();
    var winHeight = $(window).height();
    var winRatio = winHeight/winWidth;
    
    // Resize the image
    if (winRatio > ratio) {
    	$(bgDiv).height(winHeight);
        $(bgDiv).width(winHeight / ratio);
        $(bgImg).height(winHeight);
        $(bgImg).width(winHeight / ratio);
    } else {
        $(bgDiv).width(winWidth);
        $(bgDiv).height(winWidth * ratio);
        $(bgImg).width(winWidth);
        $(bgImg).height(winWidth * ratio);
    }
}