asp.net处理网络返回图片

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private
const string DefaultimageUrl = "Default.jpg";

        protected
void Page_Load(object
sender, EventArgs e)

        {

            string
a = Request.QueryString.Get("id");//这个是指的，传参的时候必须上?id=xx，不然就无效

            HttpR(a);

        }

        private
void HttpR(string
id)

        {

            string
uri = "http://xxx"
+ id + ".jpg";

            WebRequest wreq = WebRequest.Create(uri);

            try

            {

                var
wresq = (HttpWebResponse) wreq.GetResponse();

                Stream stream = wresq.GetResponseStream();

                if
(stream != null)

                {

                    Image img = Image.FromStream(stream);

                    Convert(img);

                }

            }

            catch
(Exception)

            {

                ProcessRequest();

            }

        }

        //输出默认图片

        private
static void ProcessRequest()

        {

            HttpContext context = HttpContext.Current;

            if
(context != null)

            {

                Image image = Image.FromFile(context.Server.MapPath(DefaultimageUrl));

                context.Response.ContentType = "image/jpeg";

                image.Save(context.Response.OutputStream, ImageFormat.Jpeg);

                image.Dispose();

            }

        }

        private
void Convert(Image picPath)

        {

            var
originBmp = (Bitmap) picPath;

            //根据需求调整宽高

            const
int width = 80, hight = 110;

            //绘制图片

            var
resizedBmp = new
Bitmap(width, hight);

            Graphics g = Graphics.FromImage(resizedBmp);

            g.InterpolationMode = InterpolationMode.Low;

            g.SmoothingMode = SmoothingMode.Default;

            g.CompositingQuality = CompositingQuality.HighSpeed;

            g.SmoothingMode = SmoothingMode.HighSpeed;

            g.DrawImage(originBmp, new
Rectangle(0, 0, width, hight),

                new
Rectangle(0, 0, originBmp.Width, originBmp.Height), GraphicsUnit.Pixel);

            //输出图片

            var
ms = new
MemoryStream();

            resizedBmp.Save(ms, ImageFormat.Jpeg);

            Response.ClearContent();

            Response.ContentType = "image/Jpeg";

            Response.BinaryWrite(ms.ToArray());

            //释放所有内存流

            g.Dispose();

            resizedBmp.Dispose();

            originBmp.Dispose();

            ms.Dispose();

        }