图片上传及生成缩略图

  /// <summary>         /// asp.net上传图片并生成缩略图         /// </summary>         /// <param name="upImage">HtmlInputFile控件</param>         /// <param name="sSavePath">保存的路径,些为相对服务器路径的下的文件夹</param>         /// <param name="sThumbExtension">缩略图的thumb</param>         /// <param name="intThumbWidth">生成缩略图的宽度</param>         /// <param name="intThumbHeight">生成缩略图的高度</param>         /// <returns>缩略图名称</returns>         public string UpLoadImage(HtmlInputFile upImage, string sSavePath, string sThumbExtension, int intThumbWidth, int intThumbHeight)        {            string sThumbFile = "";            string sFilename = "";            if (upImage.PostedFile != null)            {                HttpPostedFile myFile = upImage.PostedFile;                int nFileLen = myFile.ContentLength;                if (nFileLen == 0)                    return "没有选择上传图片";                //获取upImage选择文件的扩展名                 string extendName = System.IO.Path.GetExtension(myFile.FileName).ToLower();                //判断是否为图片格式                 if (extendName != ".jpg" && extendName != ".jpge" && extendName != ".gif" && extendName != ".bmp" && extendName != ".png")                    return "图片格式不正确";                byte[] myData = new Byte[nFileLen];                myFile.InputStream.Read(myData, 0, nFileLen);                sFilename = System.IO.Path.GetFileName(myFile.FileName);                int file_append = 0;                //检查当前文件夹下是否有同名图片,有则在文件名+1                 while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename)))                {                    file_append++;                    sFilename = System.IO.Path.GetFileNameWithoutExtension(myFile.FileName)                        + file_append.ToString() + extendName;                }                System.IO.FileStream newFile                    = new System.IO.FileStream(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename),                    System.IO.FileMode.Create, System.IO.FileAccess.Write);                newFile.Write(myData, 0, myData.Length);                newFile.Close();                //以上为上传原图                 try                {                    //原图加载                     using (System.Drawing.Image sourceImage = System.Drawing.Image.FromFile(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename)))                    {                        //原图宽度和高度                         int width = sourceImage.Width;                        int height = sourceImage.Height;                        int smallWidth;                        int smallHeight;                        //获取第一张绘制图的大小,(比较 原图的宽/缩略图的宽  和 原图的高/缩略图的高)                         if (((decimal)width) / height <= ((decimal)intThumbWidth) / intThumbHeight)                        {                            smallWidth = intThumbWidth;                            smallHeight = intThumbWidth * height / width;                        }                        else                        {                            smallWidth = intThumbHeight * width / height;                            smallHeight = intThumbHeight;                        }                        //判断缩略图在当前文件夹下是否同名称文件存在                         file_append = 0;                        sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) + extendName;                        while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sThumbFile)))                        {                            file_append++;                            sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) +                                file_append.ToString() + extendName;                        }                        //缩略图保存的绝对路径                         string smallImagePath = System.Web.HttpContext.Current.Server.MapPath(sSavePath) + sThumbFile;                        //新建一个图板,以最小等比例压缩大小绘制原图                         using (System.Drawing.Image bitmap = new System.Drawing.Bitmap(smallWidth, smallHeight))                        {                            //绘制中间图                             using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap))                            {                                //高清,平滑                                 g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;                                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;                                g.Clear(Color.Black);                                g.DrawImage(                                sourceImage,                                new System.Drawing.Rectangle(0, 0, smallWidth, smallHeight),                                new System.Drawing.Rectangle(0, 0, width, height),                                System.Drawing.GraphicsUnit.Pixel                                );                            }                            //新建一个图板,以缩略图大小绘制中间图                             using (System.Drawing.Image bitmap1 = new System.Drawing.Bitmap(intThumbWidth, intThumbHeight))                            {                                //绘制缩略图                                 using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap1))                                {                                    //高清,平滑                                     g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;                                    g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;                                    g.Clear(Color.Black);                                    int lwidth = (smallWidth - intThumbWidth) / 2;                                    int bheight = (smallHeight - intThumbHeight) / 2;                                    g.DrawImage(bitmap, new Rectangle(0, 0, intThumbWidth, intThumbHeight), lwidth, bheight, intThumbWidth, intThumbHeight, GraphicsUnit.Pixel);                                    g.Dispose();                                    bitmap1.Save(smallImagePath, System.Drawing.Imaging.ImageFormat.Jpeg);                                }                            }                        }                    }                }                catch                {                    //出错则删除                     System.IO.File.Delete(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename));                    return "图片格式不正确";                }                //返回缩略图名称                 return  sThumbFile;            }            return "没有选择图片";        }