上传图片并生成缩略图

    /// <summary>
    /// 上传图片并生成缩略图 
    /// </summary> 
    /// <param name="upImage">HtmlInputFile控件</param>
    /// <param name="length">文件大小</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 static string UpLoadImage(HttpPostedFile upImage, string length, string sSavePath, string sThumbExtension, int intThumbWidth, int intThumbHeight)
    {
        string sThumbFile = "";
        string sFilename = "";
        if (upImage != null)
        {
            HttpPostedFile myFile = upImage;
            int nFileLen = myFile.ContentLength;

            if (nFileLen == 0)
                return "false";
            if (nFileLen / 1024 > 1024)
                return "false";
            //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 "false";

            byte[] myData = new Byte[nFileLen];
            myFile.InputStream.Read(myData, 0, nFileLen);

            Random ro = new Random();
            int name = 1;
            string stro = ro.Next(100, 100000000).ToString() + name.ToString();//产生一个随机数用于新命名的图片
            sFilename = DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Millisecond.ToString() + stro + extendName;

            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 + sFilename;

                    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 "false";
            }
            //返回缩略图名称
            return sFilename;
        }
        return "false";
    }