关于图片转换

根据图片相对路径查找图片并转换为二进制格式

/// <summary>
        /// 图片转换
        /// </summary>
        /// <param name="strPath"></param>
        /// <returns></returns>
        private byte[] reDyte(string strPath)
        {
            byte[] bytes = null;
            try
            {
                FileStream fsMyfile = null;
                if (Directory.Exists(Server.MapPath(strPath)))
                {
                    // 以二进制方式读文件
                    fsMyfile = new FileStream(Server.MapPath(strPath), FileMode.OpenOrCreate, FileAccess.ReadWrite);
                }
                else
                {
                    fsMyfile = new FileStream(Server.MapPath(saveDir + "/default.jpg"), FileMode.OpenOrCreate, FileAccess.ReadWrite);
                }                 
                // 创建一个二进制数据流读入器，和打开的文件关联
                BinaryReader brMyfile = new BinaryReader(fsMyfile);
                // 把文件指针重新定位到文件的开始
                brMyfile.BaseStream.Seek(0, SeekOrigin.Begin);
                bytes = brMyfile.ReadBytes(Convert.ToInt32(fsMyfile.Length.ToString()));
                // 关闭以上new的各个对象
                brMyfile.Close();
            }
            catch {
                // 以二进制方式读文件
                FileStream fsMyfile = new FileStream(Server.MapPath(saveDir + "/default.jpg"), FileMode.OpenOrCreate, FileAccess.ReadWrite);
                // 创建一个二进制数据流读入器，和打开的文件关联
                BinaryReader brMyfile = new BinaryReader(fsMyfile);
                // 把文件指针重新定位到文件的开始
                brMyfile.BaseStream.Seek(0, SeekOrigin.Begin);
                bytes = brMyfile.ReadBytes(Convert.ToInt32(fsMyfile.Length.ToString()));
                // 关闭以上new的各个对象
                brMyfile.Close();
            }
            return bytes;
        }

根据网络路径将图片保存到本地

/// <summary>
        /// 保存url图片到本地
        /// </summary>
        /// <param name="url"></param>
        /// <param name="savePath"></param>
        private string SaveUrlImage(string url)
        {
            string savePath = "";
            try
            {
                HttpWebRequest webrequest = (HttpWebRequest)WebRequest.Create(url);
                HttpWebResponse webresponse = (HttpWebResponse)webrequest.GetResponse();
                if (webresponse.StatusCode == HttpStatusCode.OK)
                {
                    System.Drawing.Image image = System.Drawing.Image.FromStream(webresponse.GetResponseStream());
                    savePath = saveDir + "/" + DateTime.Now.ToString("yyyyMMddHHmmssfffff") + ".jpg";
                    image.Save(Server.MapPath(savePath)); //保存在本地文件夹
                    image.Dispose(); //释放资源
                }
            }
            catch { }
            return savePath;
        }

将二进制格式图片保存到本地

System.IO.MemoryStream ms = new System.IO.MemoryStream(imgData);
                System.Drawing.Image img = System.Drawing.Image.FromStream(ms);
                img.Save(savePath);

检查文件是否存在

Directory.Exists(severDir)

参考资料：http://developer.51cto.com/art/200908/143612.htm

http://www.oschina.net/code/snippet_222150_15091