function get_avatar_url($uid, $size = 'min')
{
	$uid = intval($uid);
	
	if (!$uid)
	{
		return G_STATIC_URL . '/common/' . $size . '-img.jpg';
	}
	
	//get avatar url in ucenter
	if (get_setting('ucenter_enabled') == 'Y')
	{
	    $user_info = AWS_APP::model('account')->get_user_info_by_uid($uid);
	    if($user_info)
	    {
    	    $uc_uid = AWS_APP::model('ucenter')->is_uc_user($user_info['email']);
        	if($uc_uid)
        	{
        	    return 'http://YOUR_UC_PATH/avatar.php?uid='. $uc_uid . '&size=small';
        	}
	    }
	}
	
	foreach (AWS_APP::config()->get('image')->avatar_thumbnail as $key => $val)
	{
		$all_size[] = $key;
	}
	
	$size = in_array($size, $all_size) ? $size : $all_size[0];
	
	$uid = sprintf("%09d", $uid);
	$dir1 = substr($uid, 0, 3);
	$dir2 = substr($uid, 3, 2);
	$dir3 = substr($uid, 5, 2);
	
	if (file_exists(get_setting('upload_dir') . '/avatar/' . $dir1 . '/' . $dir2 . '/' . $dir3 . '/' . substr($uid, - 2) . '_avatar_' . $size . '.jpg'))
	{
		return get_setting('upload_url') . '/avatar/' . $dir1 . '/' . $dir2 . '/' . $dir3 . '/' . substr($uid, - 2) . '_avatar_' . $size . '.jpg';
	}
	else
	{
		return G_STATIC_URL . '/common/' . $size . '-img.jpg';
	}
}