//调整图片大小 private static Size NewSize(int maxWidth, int maxHeight, int Width, int Height)         {             double w = 0.0;             double h = 0.0;             double sw = Convert.ToDouble(Width);             double sh = Convert.ToDouble(Height);             double mw = Convert.ToDouble(maxWidth);             double mh = Convert.ToDouble(maxHeight);             if (sw < mw && sh < mh)//如果maxWidth和maxHeight大于源图像，则缩略图的长和高不变             {                 w = sw;                 h = sh;             }             else if ((sw / sh) > (mw / mh))             {                 w = maxWidth;                 h = (w * sh) / sw;             }             else             {                 h = maxHeight;                 w = (h * sw) / sh;             }             return new Size(Convert.ToInt32(w), Convert.ToInt32(h));         }

//生成缩略图 public static void SendSmallImage(string filename, string newfile, int maxHeight, int maxWidth, string mode)         {             System.Drawing.Image img = System.Drawing.Image.FromFile(filename);//源图像的信息             System.Drawing.Imaging.ImageFormat thisformat = img.RawFormat; //源图像的格式             Size newSize = NewSize(maxWidth, maxHeight, img.Width, img.Height); //返回调整后的图像Width与Height             Bitmap outBmp = new Bitmap(maxWidth, maxHeight);             Graphics g = Graphics.FromImage(outBmp);             //设置画布的描绘质量             g.CompositingQuality = CompositingQuality.HighQuality;             g.SmoothingMode = SmoothingMode.HighQuality;             g.InterpolationMode = InterpolationMode.HighQualityBicubic;             g.Clear(Color.White);             g.DrawImage(img, new Rectangle(((maxWidth - newSize.Width) / 2), ((maxHeight - newSize.Height) / 2), newSize.Width, newSize.Height), 0, 0, img.Width, img.Height, GraphicsUnit.Pixel);             g.Dispose();             //以下代码为保存图片时，设置压缩质量             EncoderParameters encoderParams = new EncoderParameters();             long[] quality = new long[1];             quality[0] = 100;             EncoderParameter encoderParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality);             encoderParams.Param[0] = encoderParam;             //获取包含有关内置图像编码解码器的信息的ImageCodecInfo对象。             ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();             ImageCodecInfo jpegICI = null;             for (int x = 0; x < arrayICI.Length; x++)             {                 if (arrayICI[x].FormatDescription.Equals("JPEG"))                 {                     jpegICI = arrayICI[x];//设置jpeg编码                     break;                 }             }             if (jpegICI != null)             {                 outBmp.Save(newfile, jpegICI, encoderParams);             }             else             {                 outBmp.Save(newfile, thisformat);             }             img.Dispose();             outBmp.Dispose();         }

//输出图片         public static void OutPutImg(string imgFilePath)         {             FileStream fs = new FileStream(HttpContext.Current.Server.MapPath(imgFilePath), FileMode.Open, FileAccess.Read);             DateTime contentModified = System.IO.File.GetLastWriteTime(HttpContext.Current.Server.MapPath(imgFilePath));             if (IsClientCached(contentModified))             {                 HttpContext.Current.Response.StatusCode = 304;                 HttpContext.Current.Response.SuppressContent = true;             }             else             {                 byte[] mydata = new byte[fs.Length];                 int Length = Convert.ToInt32(fs.Length);                 fs.Read(mydata, 0, Length);                 fs.Close();                 HttpContext.Current.Response.OutputStream.Write(mydata, 0, Length);                 HttpContext.Current.Response.ContentType = "image/jpeg";                 HttpContext.Current.Response.End();                 HttpContext.Current.Response.Cache.SetETagFromFileDependencies();                 HttpContext.Current.Response.Cache.SetAllowResponseInBrowserHistory(true);                 HttpContext.Current.Response.Cache.SetLastModified(contentModified);             }         }

//outpuimg.ashx?src=/images/weimeidesc/8af30049-797e-4eb4-8a54-cc4de47c1694.jpg!100x100.jpg         public void ProcessRequest(HttpContext context)         {             //获取图片             string imgUrl = context.Request.QueryString["src"];             string trueFilePath = imgUrl.Split('!')[0];             //获取图片大小             int width = Convert.ToInt32(imgUrl.Split('!')[1].Replace(".jpg", "").Split('x')[0]);             int height = Convert.ToInt32(imgUrl.Split('!')[1].Replace(".jpg", "").Split('x')[1]);             //图片已经存在直接输出             if (File.Exists(context.Server.MapPath("~/" + imgUrl)))             {                 OutPutImg("~/"+imgUrl);             }             else             {                 if (!string.IsNullOrEmpty(imgUrl) && File.Exists(context.Server.MapPath("~/" + trueFilePath)))                 {                     Image originalImage = System.Drawing.Image.FromFile(context.Server.MapPath("~/" + trueFilePath));                     var newBitmap = new Bitmap(originalImage);                     //生成相应的小图并保存                     SendSmallImage(context.Server.MapPath("~/" + trueFilePath),context.Server.MapPath("~/" + imgUrl), width, height, "meiyouyisi");                     //输出                     OutPutImg("~/" + imgUrl);                 }                 else//图片如果不存在 输出默认图片                 {                     //OutPutImg(imgUrl);                 }             }         }