asp.net实现生成缩略图及加水印的方法示例

using System.IO;

using System.Drawing.Imaging;

private void Button1_ServerClick(object sender, System.EventArgs e)

{

  Graphics g=null;

  System.Drawing.Image upimage=null;

  System.Drawing.Image thumimg=null;

  System.Drawing.Image simage=null;

  Bitmap outputfile=null;

  try

  {

    string extension = Path.GetExtension(File1.PostedFile.FileName).ToUpper();

    string filename = DateTime.Now.ToString("yyyyMMddhhmmss");

    string smallpath = Server.MapPath(".")+"/smallimg/";

    string bigpath = Server.MapPath(".")+"/bigimg/";

    int width,height,newwidth,newheight;

    System.Drawing.Image.GetThumbnailImageAbort callb =new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback);

    if(!Directory.Exists(smallpath))

    Directory.CreateDirectory(smallpath);

    if(!Directory.Exists(bigpath))

    Directory.CreateDirectory(bigpath);

    Stream upimgfile = File1.PostedFile.InputStream;

    string simagefile = Server.MapPath("a8logo.jpg"); //要加水印的文件

    simage=System.Drawing.Image.FromFile(simagefile);

    upimage= System.Drawing.Image.FromStream(upimgfile); //上传的图片

    width = upimage.Width;

    height = upimage.Height;

    if(width>height)

    {

      newwidth=200;

      newheight =(int)((double)height/(double)width * (double)newwidth);

    } else

    {

      newheight=200;

      newwidth=(int)((double)width/(double)height * (double)newheight);

    }

    thumimg = upimage.GetThumbnailImage(newwidth,newheight,callb,IntPtr.Zero);

    outputfile=new Bitmap(upimage);

    g=Graphics.FromImage(outputfile);

    g.DrawImage(simage,new Rectangle(upimage.Width-simage.Width,upimage.Height-simage.Height,upimage.Width,upimage.Height),0,0,upimage.Width,upimage.Height,GraphicsUnit.Pixel);

    string newpath = bigpath + filename + extension; //原始图路径

    string thumpath = smallpath + filename + extension; //缩略图路径

    outputfile.Save(newpath);

    thumimg.Save(thumpath);

    outputfile.Dispose();

  }

  catch(Exception ex)

  {

    throw ex;

  }

  finally

  {

    if(g!=null)

    g.Dispose();

    if(thumimg!=null)

    thumimg.Dispose();

    if(upimage!=null)

    upimage.Dispose();

    if(simage!=null)

    simage.Dispose();

  }

}

public bool ThumbnailCallback()

{

  return false;

}