$(document).ready(function(){
	var originalImgHeight = $("#introImg").height();
	var originalImgWidth  = $("#introImg").width();

	resizeIntroImg(originalImgHeight, originalImgWidth);
	
	$(window).resize(function(){
		resizeIntroImg(originalImgHeight, originalImgWidth);
	});

});


function resizeIntroImg(originalImgHeight, originalImgWidth) {
	var imgHeight = $("#introImg").height();
	var imgWidth  =	$("#introImg").width();
	var windowHeight = $(window).height();
	var windowWidth = $(window).width();
	
	var new_h = 0;
	var new_w = 0;
	var marginLeft = 0;
	var marginRight = 0;
	var ratio = imgWidth / imgHeight;

	//Set the width
		new_w = windowWidth;
		new_h = new_w / ratio;
		
		marginLeft = new_w / 2;
		marginTop = new_h / 2;
		
	//Set the Height only if Needed
	if( windowHeight < new_h) { 
			
		new_h = windowHeight;
		new_w = new_h * ratio;
		
		marginTop = new_h / 2;
		marginLeft = new_w / 2;

	}
							
	if(new_w && new_h && ( new_h < originalImgHeight && new_w < originalImgWidth) ) {
		$("#introImg").width(new_w).height(new_h);
		$("#introImg").css('marginLeft','-'+marginLeft+'px');
		$("#introImg").css('marginTop','-'+marginTop+'px');
	}
	
}