function changeImg(elm, flg, suf) {
	var suffix      = suf ? suf : '_over';
	var imgObj      = getImagePath(elm);
	
	if(flg){
		elm.src     = (imgObj.name.indexOf(suffix) < 0) ? imgObj.dir + '/' + imgObj.name + suffix + '.' + imgObj.tail : imgObj.dir + '/' + imgObj.name + '.' + imgObj.tail;
	}else{
		imgObj.name = imgObj.name.replace(suffix, '');
		elm.src     = imgObj.dir + '/' + imgObj.name + '.' + imgObj.tail;
	}
	
	function getImagePath(elm){
		var a     = {};
		var path  = elm.src.split('/');
		a.dir      = path.slice(0, path.length - 1).join('/');
		a.name     = path[path.length - 1].split('.')[0];
		a.tail     = path[path.length - 1].split('.')[1];
		return a;
	}
}