.Net 上传图片并生成高清晰缩略图

在asp.net中，上传图片功能或者是常用的，生成缩略图也是常用的。baidu或者google，c#的方法也是很多的，但是一用却发现缩略图不清晰啊，缩略图片太大之类的事情，下面是我在处理图片上的代码，效果不错，所以拿出来分享，(效果能达到一些绘图软件的效果) 代码如下： /// <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";      }     <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server">     <title>无标题页</title> </head> <body>     <form id="form1" runat="server">     <div>                 <input id="File1" runat="server" type="file" /></div><asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" />     </form> </body> </html>      protected void Button1_Click(object sender, EventArgs e)      {         string a = this.UpLoadImage(this.File1, "UpLoad/", "thumb_", 118, 118);        }