//ロールオーバー設定
(function($){
	var name_space = 'rollover';

	$(function (){
		$.fn[name_space]();
	});

	$.fn[name_space] = function(options){
		//いったん退避
		var elements = this;
		//設定
		var settings = $.extend({
			selector: '.'+name_space,
			postfix: '_on'
		}, options);
		//初期化
		$(settings.selector).each(function(){
			this.originalSrc = $(this).attr('src');
			this.rolloverSrc = this.originalSrc.replace(/(\.gif|\.jpg|\.png)$/, settings.postfix+"$1");
			this.rolloverImg = new Image;
			this.rolloverImg.src = this.rolloverSrc;
		});
		//ロールオーバー設定
		$(settings.selector).hover(function(){
			$(this).attr('src',this.rolloverSrc);
		},function(){
			$(this).attr('src',this.originalSrc);
		});
		//method chain
		return this;
	};
})(jQuery);