/// <summary>
    /// 标题图片大小
    /// </summary>
    public enum TitileImageSize
    {
        Small,
        Big
    }
    /// <summary>
    /// 图片帮助类
    /// </summary>
    public static class ImageHelper
    {
        /// <summary>
        /// 获取图片缩略图URL
        /// </summary>
        /// <param name="webUrl">站点路径(如：SPContext.Current.Site.Url)</param>
        /// <param name="sourceImageUrl">源图路径(相对站点的路径,如:"xxx/xxx.jpg")</param>
        /// <returns>缩略图URL</returns>
        public static string GetTitleImageUrl(string webUrl, string sourceImageUrl,TitileImageSize size)
        {
            string result = string.Empty;            
            string temp = string.Empty;//将最后一个"/"替换为"/_t/",替换的逻辑在ReplaceLastGang方法中实现
            //没有这步的话，当图片库在子级站点中的时将会出飞机
            Regex myRegex = new Regex("/");
            MatchEvaluator myMatchEvaluator = new MatchEvaluator(ReplaceLastGang);
            temp=myRegex.Replace(sourceImageUrl, myMatchEvaluator);
            temp = temp.Replace(".", "_");
            

            switch (size)
            {
                case TitileImageSize.Small:
                    //temp = "/_t/";
                    break;
                case TitileImageSize.Big:
                    temp = temp.Replace("/_t/", "/_w/");
                    break;
                default:
                    break;
            }

            result