$(document).ready(function () {
	$('#mainimage img').hide().load(function () { $(this).show(); viewport(); $(this).hide().fadeIn(800);  });
});

$(window).resize(viewport);

function viewport() {
	var vh = $(window).height() - $('#header').outerHeight();
	$('#mainimage').height(vh);
	var vw = $('#mainimage').width();
	var ih = $('#mainimage img').height();
	var iw = $('#mainimage img').width();
	if (vh / vw > ih / iw) {
		$('#mainimage img').width('auto');
		$('#mainimage img').height(vh);
	}
	else {
		$('#mainimage img').width(vw);
		$('#mainimage img').height('auto');
	}
	ih = $('#mainimage img').height();
	iw = $('#mainimage img').width();
	$('#mainimage img').css({ top: (-ih+vh) / 2, left: (-iw+vw) / 2 });

}