Render Hi-Res IMGs for Retina Displays (JavaScript)

RWD-HD-IMG.js

/**
 * Retina image update script. Invoke with Retina.render().
 * Retina.render() may be passed a selector for img selection.
 * The default filter looks for imgs with data-scale="retina".
 * @param {string|function} expr	A CSS selector expression or jQuery filter function.
 * @return {boolean|collection}		Returns false or (for Retina displays) the images updated.
 * @author Joe Johnson (joe.johnson@icrossing.com)
 */
(function(ns,$){
	ns.Retina = {
		render: (function(isRetina){
			return isRetina ? function(expr){
				var r1 = /retina/i, r2 = /\d{3}/,
					filter = expr ? expr : function(){
						return r1.test($(this).data("scale"));
					};
				return $("img").filter(filter).each(function(){
					this.src = this.src.replace(r2,function(m){
						return (parseInt(m,10)>=640 ? m : 2*m);
					});
				});
			} : function(){ return false; };
		})(ns.devicePixelRatio && (ns.devicePixelRatio > 1))
	};
})(window,jQuery);