上传图片并且生成可以控制大小图片清晰度的方法

      private void Upload_Click(object sender, System.EventArgs e)        {            if(myFile.PostedFile !=null)            {                // 检查文件扩展名字                HttpFileCollection files  = HttpContext.Current.Request.Files;                HttpPostedFile postedFile = files[0];                string fileName,fileExtension,file_id,file_path;

                //取出精确到毫秒的时间做文件的名称                int year = System.DateTime.Now.Year;                int month = System.DateTime.Now.Month;                int day = System.DateTime.Now.Day;                int hour = System.DateTime.Now.Hour;                int minute = System.DateTime.Now.Minute;                int second = System.DateTime.Now.Second;                int millisecond = System.DateTime.Now.Millisecond;                string my_file_id = year.ToString() + month.ToString() + day.ToString() + hour.ToString() + minute.ToString() + second.ToString() + millisecond.ToString();

                //获得文件类型                fileName = System.IO.Path.GetFileName(postedFile.FileName);                fileExtension = System.IO.Path.GetExtension(fileName);

                //重新命名文件，防止重复                file_id = "topnews_"+my_file_id+fileExtension;                file_path = "images/article_images/"+file_id;

                //文件上传到服务器的根目录                postedFile.SaveAs(Request.PhysicalApplicationPath+@"images/article_images/"+ file_id);

                //处理图片大小                int width,height,level;                width=120;                height=90;                level=100;//从1-100                GetThumbnailImage(width,height,level,file_id);            }        }

        //生成缩略图函数        public void GetThumbnailImage(int width,int height,int level,string file_id)        {            string newfile= Request.PhysicalApplicationPath+"images/article_images/"+"top_"+ file_id;            System.Drawing.Image oldimage = System.Drawing.Image.FromFile(Request.PhysicalApplicationPath+"images/article_images/"+ file_id);            System.Drawing.Image thumbnailImage = oldimage.GetThumbnailImage(width, height,new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback), IntPtr.Zero);            Bitmap output=new Bitmap(thumbnailImage);

            //处理JPG质量的函数            ImageCodecInfo[] codecs=ImageCodecInfo.GetImageEncoders();             ImageCodecInfo ici=null;            foreach(ImageCodecInfo codec in codecs){if(codec.MimeType=="image/jpeg")ici=codec;}            EncoderParameters ep=new EncoderParameters();            ep.Param[0]=new EncoderParameter(Encoder.Quality,(long)level);            output.Save(newfile,ici,ep);

            //释放所有使用对象            ep.Dispose();            output.Dispose();            oldimage.Dispose();            thumbnailImage.Dispose();

            //删除源图片            string file_path = "images/article_images/"+"top_"+file_id;            usageIO.DeletePath(Request.PhysicalApplicationPath+"images/article_images/"+ file_id);            Response.Write("<script >parent.Form1.A_Simg.value ='"+file_path+"';location.replace('Upload_Img.aspx')</script>");        }

        bool ThumbnailCallback()        {            return false;        }