snippet.js

(function( jQuery ) {

jQuery.ajaxPrefilter( "img", function( settings ) {
  if ( settings.cache == null ) {
    settings.cache = false;
  }
  settings.type = "GET";
  settings.async = true;
});

jQuery.ajaxTransport( "img", function( settings ) {
  var callback, $img, img, prop;
  var xport = {
    send: function( _, complete ) {
      callback = function( success ) {
        if ( success ) {
          complete( 200, "OK", { img: img } );
        } else {
          $img.remove();
          if ( success === false ) {
            complete( 404, "Not Found" );
          }
        }
      };
      
      $img = $( "<img>", {
        src: settings.url
      });
      img = $img[0];
      prop = typeof img.naturalWidth === "undefined" ? "width" : "naturalWidth";

      if ( img.complete ) {
        callback( !!img[ prop ] );
      } else {
        $img.bind( "load error", function( event ) {
          callback( event.type == "load" );
        });        
      }
      
    },
    abort: function() {
      if ( callback ) {
        callback();
      }
    }
  };

  return xport;
});

})( jQuery );