public partial class WebForm4 : System.Web.UI.Page
      {
          // 原始圖片路徑
          private string path;
          private System.Drawing.Bitmap bitmap;     
          private System.Drawing.Graphics graphics;
          string Message = "<script>alert(/"{0}/");</script>";
          protected void Page_Load(object sender, EventArgs e)
          {
              if (!Page.IsPostBack)
              {
                  this.txtPicPath.Text = Server.MapPath("/test.jpg");
              }
              path = this.txtPicPath.Text.Trim();
              if (!System.IO.File.Exists(path))
              {
                  MessageShow("指定的源文件不存在！");
                  return;
              }
          }
          // 打水印Logo
          protected void btnLogo_Click(object sender, EventArgs e)
          {
              string log = txtLog.Text.Trim();
              if (log.Length < 1)
              {
                  MessageShow("請輸入水印字符！");
                  return;
              }

              bitmap = new Bitmap(path);
              graphics = Graphics.FromImage(bitmap);
              graphics.DrawString(log, new Font("宋體", 16), System.Drawing.Brushes.GreenYellow, new PointF(bitmap.Width / 2 - (log.Length) * 5, bitmap.Height / 2));
              try
              {
                  bitmap.Save(Server.MapPath("./_Log.jpg"), System.Drawing.Imaging.ImageFormat.Jpeg);
                  MessageShow("已經生成水印圖片，路徑為" + @Server.MapPath("./_log.jpg").Replace("http://", "////"));

              }
              catch (Exception ex)
              {
                  MessageShow("生成圖片錯誤！" + ex.Message);
                  throw;
              }
              graphics.Dispose();
              bitmap.Dispose();
          }
          private void MessageShow(string msg)
          {
              Page.ClientScript.RegisterStartupScript(Page.GetType(), "Message", string.Format(Message, msg));

          }
          //放大X*X倍
          protected void btnBig_Click(object sender, EventArgs e)
          {
              int i = int.Parse(txtBig.Text.Trim());
              System.Drawing.Image img = System.Drawing.Image.FromFile(path);
              bitmap = new Bitmap(img.Width * i, img.Height * i);
              graphics = Graphics.FromImage(bitmap);
              graphics.DrawImage(img, 0, 0, img.Width * i, img.Height * i);
              try
              {
                  bitmap.Save(Server.MapPath("./_Big.jpg"), System.Drawing.Imaging.ImageFormat.Jpeg);
                  MessageShow("已經生成圖片，路徑為" + @Server.MapPath("./_Big.jpg").Replace("http://", "////"));

              }
              catch (Exception ex)
              {
                  MessageShow("生成圖片錯誤！" + ex.Message);
                  throw;
              }
              graphics.Dispose();
              bitmap.Dispose();
          }

          //縮小為原始圖像的1/(X*X)
          protected void btnSmall_Click(object sender, EventArgs e)
          {
              float i = float.Parse(txtBig.Text.Trim());
              System.Drawing.Image img = System.Drawing.Image.FromFile(path);
              int w = Convert.ToInt32(img.Width / i);
              int h = Convert.ToInt32(img.Height / i);

              // 防止過度變形
              if (w < 1) w = 10;
              if (h < 1) h = 0;
              bitmap = new Bitmap(w, h);
              graphics = Graphics.FromImage(bitmap);
              graphics.DrawImage(img, 0, 0, w, h);
              try
              {
                  bitmap.Save(Server.MapPath("./_Small.jpg"), System.Drawing.Imaging.ImageFormat.Jpeg);
                  MessageShow("已經生成圖片，路徑為" + @Server.MapPath("./_Small.jpg").Replace("http://", "////"));

              }
              catch (Exception ex)
              {
                  MessageShow("生成圖片錯誤！" + ex.Message);
                  throw;
              }
              graphics.Dispose();
              bitmap.Dispose();
          }
//傾斜（ 右轉90度）
          protected void btnIncline_Click(object sender, EventArgs e)
          {
              System.Drawing.Image img = System.Drawing.Image.FromFile(path);
              // 圖像旋轉，可以利用RotateFlipType的枚舉值，在編程的時候，IDE會自動顯示每一個枚舉的意思
              img.RotateFlip(RotateFlipType.Rotate90FlipXY);
              bitmap = new Bitmap(img);
              graphics = Graphics.FromImage(bitmap);
              graphics.DrawImage(img, new Point(0, 0));
              try
              {
                  bitmap.Save(Server.MapPath("./_Incline.jpg"), System.Drawing.Imaging.ImageFormat.Jpeg);
                  MessageShow("已經生成圖片，路徑為" + @Server.MapPath("./_Incline.jpg").Replace("http://", "////"));

              }
              catch (Exception ex)
              {
                  MessageShow("生成圖片錯誤！" + ex.Message);
                  throw;
              }
              graphics.Dispose();
              bitmap.Dispose();
          }

          // 圖像壓扁
          protected void btnStave_Click(object sender, EventArgs e)
          {
              System.Drawing.Image img = System.Drawing.Image.FromFile(path);
              // 寬度不變
              int w = img.Width;
              //    高度為原始高度的1/2
              int h = img.Height / 2;

              // 防止過度變形
              if (w < 1) w = 10;
              if (h < 1) h = 0;
              bitmap = new Bitmap(w, h);
              graphics = Graphics.FromImage(bitmap);
              graphics.DrawImage(img, 0, 0, w, h);
              try
              {
                  bitmap.Save(Server.MapPath("./_Stave.jpg"), System.Drawing.Imaging.ImageFormat.Jpeg);
                  MessageShow("已經生成圖片，路徑為" + @Server.MapPath("./_Stave.jpg").Replace("http://", "////"));

              }
              catch (Exception ex)
              {
                  MessageShow("生成圖片錯誤！" + ex.Message);
                  throw;
              }
              graphics.Dispose();
              bitmap.Dispose();
          }
          //圖像拉寬
          protected void btnElongate_Click(object sender, EventArgs e)
          {
              System.Drawing.Image img = System.Drawing.Image.FromFile(path);
              // 放大寬度
              int w = img.Width / 2;
              // 高度不變
              int h = img.Height;

              // 防止過度變形
              if (w < 1) w = 10;
              if (h < 1) h = 0;
              bitmap = new Bitmap(w, h);
              graphics = Graphics.FromImage(bitmap);
              graphics.DrawImage(img, 0, 0, w, h);
              try
              {
                  bitmap.Save(Server.MapPath("./_Elongate.jpg"), System.Drawing.Imaging.ImageFormat.Jpeg);
                  MessageShow("已經生成圖片，路徑為" + @Server.MapPath("./_Elongate.jpg").Replace("http://", "////"));

              }
              catch (Exception ex)
              {
                  MessageShow("生成圖片錯誤！" + ex.Message);
                  throw;
              }
              graphics.Dispose();
              bitmap.Dispose();
          }
      }