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Result
JavaScript
CSS
HTML

if (window.devicePixelRatio > 1)
      $('img').each(function() {
          var t = $(this);
        t.attr('src', t.attr('src').replace(/(\.[a-z]+)$/i, "@2x$1"));
      });

<img src="http://kachibito.net/wp-content/uploads/2012/05/simpler000.jpg">