ASP.NET2.0文件上传以及图片处理 (转载)

 

1.最简单的单文件上传(没花头)
2.多文件上传
3.客户端检查上传文件类型(以上传图片为例)
4.服务器端检查上传文件类型(以上传图片为例)
5.服务器端检查上传文件类型(可以检测真正文件名)
6.上传文件文件名唯一性处理(时间戳+SessionID)
7.上传图片生成等比例缩略图
8.上传图片加水印(文字水印，图片水印，文字+图片水印)
9.

1.最简单的单文件上传(没花头)

效果图：

说明：这是最基本的文件上传，在asp.net1.x中没有这个FileUpload控件，只有html的上传控件，那时候要把html控件转化为服务器控件，很不好用。其实所有文件上传的美丽效果都是从这个FileUpload控件衍生，第一个例子虽然简单却是根本。

后台代码：
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void bt_upload_Click(object sender, EventArgs e)
    {
        try
        {
            if (FileUpload1.PostedFile.FileName == "")
            {
                this.lb_info.Text = "请选择文件！";
            }
            else
            {
                string filepath = FileUpload1.PostedFile.FileName;
                string filename = filepath.Substring(filepath.LastIndexOf("//") + 1);
                string serverpath = Server.MapPath("images/") + filename;
                FileUpload1.PostedFile.SaveAs(serverpath);
                this.lb_info.Text = "上传成功！";
            }
        }
        catch (Exception ex)
        {
            this.lb_info.Text = "上传发生错误！原因是：" + ex.ToString();
        }
    }
}

前台代码：
<table style="width: 343px">
            <tr>
                <td style="width: 100px">
                    单文件上传</td>
                <td style="width: 100px">
                </td>
            </tr>
            <tr>
                <td style="width: 100px">
                    <asp:FileUpload ID="FileUpload1" runat="server" Width="475px" />
                    </td>
                <td style="width: 100px">
                    <asp:Button ID="bt_upload" runat="server" OnClick="bt_upload_Click" Text="上传" /></td>
            </tr>
            <tr>
                <td style="width: 100px; height: 21px;">
                    <asp:Label ID="lb_info" runat="server" ForeColor="Red" Width="183px"></asp:Label></td>
                <td style="width: 100px; height: 21px">
                </td>
            </tr>
        </table> 

2.多文件上传

效果图：

后台代码：
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void bt_upload_Click(object sender, EventArgs e)
    {
       
            if ((FileUpload1.PostedFile.FileName == "" && FileUpload2.PostedFile.FileName == "")&&FileUpload3.PostedFile.FileName == "")
            {
                this.lb_info.Text = "请选择文件！";
            }
            else
            {
                HttpFileCollection myfiles = Request.Files;
                for (int i = 0; i < myfiles.Count; i++)
                {
                    HttpPostedFile mypost = myfiles[i];
                    try
                    {
                        if (mypost.ContentLength > 0)
                        {
                             string filepath = mypost.FileName;
                             string filename = filepath.Substring(filepath.LastIndexOf("//") + 1);
                             string serverpath = Server.MapPath("images/") + filename;
                             mypost.SaveAs(serverpath);
                             this.lb_info.Text = "上传成功！";
                        }
                    }
                    catch (Exception error)
                    {
                        this.lb_info.Text = "上传发生错误！原因：" + error.ToString();
                    }

                }
              
            }
        }
      
    }

前台代码：
 <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!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>多文件上传 清清月儿http://blog.csdn.net/21aspnet/</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <table style="width: 343px">
            <tr>
                <td style="width: 100px">
                    多文件上传</td>
                <td style="width: 100px">
                </td>
            </tr>
            <tr>
                <td style="width: 100px">
                    <asp:FileUpload ID="FileUpload1" runat="server" Width="475px" />
                    </td>
                <td style="width: 100px">
                    </td>
            </tr>
            <tr>
                <td style="width: 100px">
                    <asp:FileUpload ID="FileUpload2" runat="server" Width="475px" /></td>
                <td style="width: 100px">
                </td>
            </tr>
            <tr>
                <td style="width: 100px">
                    <asp:FileUpload ID="FileUpload3" runat="server" Width="475px" /></td>
                <td style="width: 100px">
                </td>
            </tr>
            <tr>
                <td style="width: 100px">
                    <asp:Button ID="bt_upload" runat="server" OnClick="bt_upload_Click" Text="一起上传" />
                    <asp:Label ID="lb_info" runat="server" ForeColor="Red" Width="183px"></asp:Label></td>
                <td style="width: 100px">
                </td>
            </tr>
        </table>
   
    </div>
    </form>
</body>
</html>

3.客户端检查上传文件类型(以上传图片为例)

效果图：

后台代码和1.最简单的单文件上传一样；
前台代码：
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!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>清清月儿 http://blog.csdn.net/21aspnet</title>
<script   language="javascript"> 
 function Check_FileType()
{
var str=document.getElementById("FileUpload1").value;
 var pos = str.lastIndexOf(".");
 var lastname = str.substring(pos,str.length) 
 if (lastname.toLowerCase()!=".jpg" && lastname.toLowerCase()!=".gif")
 {
     alert("您上传的文件类型为"+lastname+"，图片必须为.jpg,.gif类型");
     return false;
 }
 else
 {
  return true;
 }
}
 </script> 

</head>
<body>
    <form id="form1" runat="server">
    <div>
        <table style="width: 343px">
            <tr>
                <td style="width: 104px">
                    文件上传判断</td>
                <td style="width: 100px">
                </td>
            </tr>
            <tr>
                <td style="width: 104px">
                    <asp:FileUpload ID="FileUpload1" runat="server" Width="400px" />
                    </td>
                <td style="width: 100px">
                    <asp:Button ID="bt_upload" runat="server" OnClick="bt_upload_Click" Text="上传"  OnClientClick="return Check_FileType()"/></td>
            </tr>
            <tr>
                <td style="width: 104px; height: 21px;">
                    <asp:Label ID="lb_info" runat="server" ForeColor="Red" Width="183px"></asp:Label></td>
                <td style="width: 100px; height: 21px">
                </td>
            </tr>
        </table>
   
    </div>
    </form>
</body>
</html>
说明：点击上传时先触发客户端事件Check_FileType；

4.服务器端检查上传文件类型(以上传图片为例)

效果图：

后台代码：
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void bt_upload_Click(object sender, EventArgs e)
    {
        try
        {
            if (FileUpload1.PostedFile.FileName == "")
            {
                this.lb_info.Text = "请选择文件！";
            }
            else
            {
                string filepath = FileUpload1.PostedFile.FileName;
                if (IsAllowedExtension(FileUpload1) == true)
                {

                    string filename = filepath.Substring(filepath.LastIndexOf("//") + 1);
                    string serverpath = Server.MapPath("images/") + filename;
                    FileUpload1.PostedFile.SaveAs(serverpath);
                    this.lb_info.Text = "上传成功！";
                }
                else
                {
                    this.lb_info.Text = "请上传图片";
                }
            }
        }
        catch (Exception error)
        {
            this.lb_info.Text = "上传发生错误！原因：" + error.ToString();
        }
    }
   public static bool IsAllowedExtension(FileUpload hifile)
    {
        string strOldFilePath = "", strExtension = "";
        string[] arrExtension =   { ".gif", ".jpg", ".jpeg", ".bmp", ".png" };
        if (hifile.PostedFile.FileName != string.Empty)
        {
            strOldFilePath = hifile.PostedFile.FileName;
            strExtension = strOldFilePath.Substring(strOldFilePath.LastIndexOf("."));
            for (int i = 0; i < arrExtension.Length; i++)
            {
                if (strExtension.Equals(arrExtension[i]))
                {
                    return true;
                }
            }
        }
        return false;
    }  

}

 5.服务器端检查上传文件类型(可以检测真正文件名)
其实方法4并不好，因为用户可以把XXX.txt伪装为XXX.jpg。

效果图：

后台代码：
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class _Default : System.Web.UI.Page
{
    //清清月儿 http://blog.csdn.net/21aspnet
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void bt_upload_Click(object sender, EventArgs e)
    {
        try
        {
            if (FileUpload1.PostedFile.FileName == "")
            {
                this.lb_info.Text = "请选择文件！";
            }
            else
            {
                string filepath = FileUpload1.PostedFile.FileName;
                if (IsAllowedExtension(FileUpload1) == true)
                {
                    string filename = filepath.Substring(filepath.LastIndexOf("//") + 1);
                    string serverpath = Server.MapPath("images/") + filename;
                    FileUpload1.PostedFile.SaveAs(serverpath);
                    this.lb_info.Text = "上传成功！";
                }
                else
                {
                    this.lb_info.Text = "请上传图片";
                }
            }
        }
        catch (Exception error)
        {
            this.lb_info.Text = "上传发生错误！原因：" + error.ToString();
        }
    }
    public static bool IsAllowedExtension(FileUpload hifile)
    {
        System.IO.FileStream fs = new System.IO.FileStream(hifile.PostedFile.FileName, System.IO.FileMode.Open, System.IO.FileAccess.Read);
        System.IO.BinaryReader r = new System.IO.BinaryReader(fs);
        string fileclass = "";
        byte buffer;
        try
        {
            buffer = r.ReadByte();
            fileclass = buffer.ToString();
            buffer = r.ReadByte();
            fileclass += buffer.ToString();

        }
        catch
        {
          
        }
        r.Close();
        fs.Close();
        if (fileclass == "255216" || fileclass == "7173")//说明255216是jpg;7173是gif;6677是BMP,13780是PNG;7790是exe,8297是rar
        {
            return true;
        }
        else
        {
            return false;
        }

    }  

}

6.上传文件文件名唯一性处理(时间戳+SessionID)

效果图：

说明：年月日时分秒+临时session+原文件名 如果大家怕还会重复可以加GUID
后台代码：

try
        {
            if (FileUpload1.PostedFile.FileName == "")
            {
                this.lb_info.Text = "请选择文件！";
            }
            else
            {
                string filepath = FileUpload1.PostedFile.FileName;
                string filename = filepath.Substring(filepath.LastIndexOf("//") + 1);
                string serverpath = Server.MapPath("images/") + System.DateTime.Now.ToString("yyy-MM-dd-hh-mm-ss") + Session.SessionID + filename;
                FileUpload1.PostedFile.SaveAs(serverpath);
                this.lb_info.Text = "上传成功！";
            }
        }
        catch (Exception error)
        {
            this.lb_info.Text = "上传发生错误！原因：" + error.ToString();
        }

注：GUID的方法：Guid myGuid=Guid.NewGuid();

7.上传图片生成等比例缩略图

效果图：

缩略图代码：
ImageThumbnail.cs
using System;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;

public class ImageThumbnail
{
    public Image ResourceImage;
    private int ImageWidth;
    private int ImageHeight;
    public string ErrorMessage;

    public ImageThumbnail(string ImageFileName)
    {
        ResourceImage = Image.FromFile(ImageFileName);
        ErrorMessage = "";
    }

    public bool ThumbnailCallback()
    {
        return false;
    }

    // 方法1，按大小
    public bool ReducedImage(int Width, int Height, string targetFilePath)
    {
        try
        {
            Image ReducedImage;
            Image.GetThumbnailImageAbort callb = new Image.GetThumbnailImageAbort(ThumbnailCallback);
            ReducedImage = ResourceImage.GetThumbnailImage(Width, Height, callb, IntPtr.Zero);
            ReducedImage.Save(@targetFilePath, ImageFormat.Jpeg);
            ReducedImage.Dispose();
            return true;
        }
        catch (Exception e)
        {
            ErrorMessage = e.Message;
            return false;
        }
    }

    // 方法2，按百分比  缩小60% Percent为0.6 targetFilePath为目标路径
    public bool ReducedImage(double Percent, string targetFilePath)
    {
        try
        {
            Image ReducedImage;
            Image.GetThumbnailImageAbort callb = new Image.GetThumbnailImageAbort(ThumbnailCallback);
            ImageWidth = Convert.ToInt32(ResourceImage.Width * Percent);
            ImageHeight = (ResourceImage.Height)*ImageWidth/ ResourceImage.Width;//等比例缩放
            ReducedImage = ResourceImage.GetThumbnailImage(ImageWidth, ImageHeight, callb, IntPtr.Zero);
            ReducedImage.Save(@targetFilePath, ImageFormat.Jpeg);
            ReducedImage.Dispose();
            return true;
        }
        catch (Exception e)
        {
            ErrorMessage = e.Message;
            return false;
        }
    }

}

后台代码：
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class _Default : System.Web.UI.Page
{

    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void bt_upload_Click(object sender, EventArgs e)
    {
        try
        {
            if (FileUpload1.PostedFile.FileName == "")
            {
                this.lb_info.Text = "请选择文件！";
            }
            else
            {
                string filepath = FileUpload1.PostedFile.FileName;
                string filename = filepath.Substring(filepath.LastIndexOf("//") + 1);
                string serverpath1 = Server.MapPath("images/") + filename;
                string serverpath2 = Server.MapPath("images/") + System.DateTime.Now.ToString("yyy-MM-dd-hh-mm-ss") + Session.SessionID + filename;
                FileUpload1.PostedFile.SaveAs(serverpath1);
                ImageThumbnail img = new ImageThumbnail(filepath);
                img.ReducedImage(0.4, serverpath2);//0.4表示缩小40%
                this.lb_info.Text = "上传成功！";
            }
        }
        catch (Exception error)
        {
            this.lb_info.Text = "上传发生错误！原因：" + error.ToString();
        }
    }

}

8.上传图片加水印(文字水印，图片水印，文字+图片水印)

效果图：
原图

水印

给图片加水印以后（注意右上角+正下方）

代码：
DrawImg.cs  出自http://www.codeproject.com/csharp/watermark.asp
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;
public class DrawImg
{
 private string  WorkingDirectory = string.Empty ; //路径
 private string  ImageName = string.Empty;   //被处理的图片
 private string  ImageWater = string.Empty;  //水印图片
 private string  FontString = string.Empty;  //水印文字
 

 enum DealType{NONE,WaterImage,WaterFont,DoubleDo}; //枚举命令

 private DealType dealtype;
 

 public DrawImg()
 {}

 public string PublicWorkingDirectory
 {
  get
  {
   return WorkingDirectory;
  }
  set
  {
   WorkingDirectory = value;
  }
 }

 public string PublicImageName
 {
  get
  {
   return ImageName;
  }
  set
  {
   ImageName = value;
  }
 }

 public string PublicImageWater
 {
  get
  {
   return ImageWater;
  }
  set  //设置了水印图片的话说明是要水印图片效果的
  {
   dealtype = DealType.WaterImage;
   ImageWater = value;
  }
 }

 public string PublicFontString
 {
  get
  {
   return FontString;
  }
  set //设置了水印文字的话说明是要水印文字效果的
  {
   dealtype = DealType.WaterFont;
   FontString = value;
  }
 }

 public void DealImage()
 {
  IsDouble();

  switch( dealtype )
  {
   case DealType.WaterFont: WriteFont(); break;
   case DealType.WaterImage: WriteImg(); break;
   case DealType.DoubleDo: WriteFontAndImg(); break;
  }

 }

 private void IsDouble()
 {
  if(ImageWater+""!="" && FontString+""!="")
  {
            dealtype = DealType.DoubleDo;
  }
 }

 private void WriteFont()
 {
  //set a working directory
  //string WorkingDirectory = @"C:/Watermark_src/WaterPic";

  //define a string of text to use as the Copyright message
  //string Copyright = "Copyright ?2002 - AP Photo/David Zalubowski";

  //create a image object containing the photograph to watermark
  Image imgPhoto = Image.FromFile(WorkingDirectory + ImageName);
  int phWidth = imgPhoto.Width;
  int phHeight = imgPhoto.Height;

  //create a Bitmap the Size of the original photograph
  Bitmap bmPhoto = new Bitmap(phWidth, phHeight, PixelFormat.Format24bppRgb);

  bmPhoto.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);

  //load the Bitmap into a Graphics object
  Graphics grPhoto = Graphics.FromImage(bmPhoto);

  //------------------------------------------------------------
  //Step #1 - Insert Copyright message
  //------------------------------------------------------------

  //Set the rendering quality for this Graphics object
  grPhoto.SmoothingMode = SmoothingMode.AntiAlias;

  //Draws the photo Image object at original size to the graphics object.
  grPhoto.DrawImage(
   imgPhoto,                               // Photo Image object
   new Rectangle(0, 0, phWidth, phHeight), // Rectangle structure
   0,                                      // x-coordinate of the portion of the source image to draw.
   0,                                      // y-coordinate of the portion of the source image to draw.
   phWidth,                                // Width of the portion of the source image to draw.
   phHeight,                               // Height of the portion of the source image to draw.
   GraphicsUnit.Pixel);                    // Units of measure

  //-------------------------------------------------------
  //to maximize the size of the Copyright message we will
  //test multiple Font sizes to determine the largest posible
  //font we can use for the width of the Photograph
  //define an array of point sizes you would like to consider as possiblities
  //-------------------------------------------------------
  int[] sizes = new int[]{16,14,12,10,8,6,4};

  Font crFont = null;
  SizeF crSize = new SizeF();

  //Loop through the defined sizes checking the length of the Copyright string
  //If its length in pixles is less then the image width choose this Font size.
  for (int i=0 ;i<7; i++)
  {
   //set a Font object to Arial (i)pt, Bold
   //crFont = new Font("arial", sizes[i], FontStyle.Bold);

   crFont = new Font("arial",sizes[i],FontStyle.Bold);

   //Measure the Copyright string in this Font
   crSize = grPhoto.MeasureString(FontString, crFont);

   if((ushort)crSize.Width < (ushort)phWidth)
    break;
  }

  //Since all photographs will have varying heights, determine a
  //position 5% from the bottom of the image
  int yPixlesFromBottom = (int)(phHeight *.05);

  //Now that we have a point size use the Copyrights string height
  //to determine a y-coordinate to draw the string of the photograph
  float yPosFromBottom = ((phHeight - yPixlesFromBottom)-(crSize.Height/2));

  //Determine its x-coordinate by calculating the center of the width of the image
  float xCenterOfImg = (phWidth/2);

  //Define the text layout by setting the text alignment to centered
  StringFormat StrFormat = new StringFormat();
  StrFormat.Alignment = StringAlignment.Center;

  //define a Brush which is semi trasparent black (Alpha set to 153)
  SolidBrush semiTransBrush2 = new SolidBrush(Color.FromArgb(153, 0, 0, 0));

  //Draw the Copyright string
  grPhoto.DrawString(FontString,                 //string of text
   crFont,                                   //font
   semiTransBrush2,                           //Brush
   new PointF(xCenterOfImg+1,yPosFromBottom+1),  //Position
   StrFormat);

  //define a Brush which is semi trasparent white (Alpha set to 153)
  SolidBrush semiTransBrush = new SolidBrush(Color.FromArgb(153, 255, 255, 255));

  //Draw the Copyright string a second time to create a shadow effect
  //Make sure to move this text 1 pixel to the right and down 1 pixel
  grPhoto.DrawString(FontString,                 //string of text
   crFont,                                   //font
   semiTransBrush,                           //Brush
   new PointF(xCenterOfImg,yPosFromBottom),  //Position
   StrFormat);   
  
  imgPhoto = bmPhoto;
  grPhoto.Dispose();

  //save new image to file system.
  imgPhoto.Save(WorkingDirectory + ImageName + "_finally.jpg", ImageFormat.Jpeg);
  imgPhoto.Dispose();
  
  //Text alignment
 }

 private void WriteImg()
 {
  //set a working directory
  //string WorkingDirectory = @"C:/Watermark_src/WaterPic";

  //create a image object containing the photograph to watermark
  Image imgPhoto = Image.FromFile(WorkingDirectory + ImageName);
  int phWidth = imgPhoto.Width;
  int phHeight = imgPhoto.Height;

  //create a Bitmap the Size of the original photograph
  Bitmap bmPhoto = new Bitmap(phWidth, phHeight, PixelFormat.Format24bppRgb);

  bmPhoto.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);

  //load the Bitmap into a Graphics object
  Graphics grPhoto = Graphics.FromImage(bmPhoto);

  //create a image object containing the watermark
  Image imgWatermark = new Bitmap(WorkingDirectory + ImageWater);
  int wmWidth = imgWatermark.Width;
  int wmHeight = imgWatermark.Height;

  //Set the rendering quality for this Graphics object
  grPhoto.SmoothingMode = SmoothingMode.AntiAlias;

  //Draws the photo Image object at original size to the graphics object.
  grPhoto.DrawImage(
   imgPhoto,                               // Photo Image object
   new Rectangle(0, 0, phWidth, phHeight), // Rectangle structure
   0,                                      // x-coordinate of the portion of the source image to draw.
   0,                                      // y-coordinate of the portion of the source image to draw.
   phWidth,                                // Width of the portion of the source image to draw.
   phHeight,                               // Height of the portion of the source image to draw.
   GraphicsUnit.Pixel);                    // Units of measure

  //------------------------------------------------------------
  //Step #2 - Insert Watermark image
  //------------------------------------------------------------

  //Create a Bitmap based on the previously modified photograph Bitmap
  Bitmap bmWatermark = new Bitmap(bmPhoto);
  bmWatermark.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);
  //Load this Bitmap into a new Graphic Object
  Graphics grWatermark = Graphics.FromImage(bmWatermark);

  //To achieve a transulcent watermark we will apply (2) color
  //manipulations by defineing a ImageAttributes object and
  //seting (2) of its properties.
  ImageAttributes imageAttributes = new ImageAttributes();

  //The first step in manipulating the watermark image is to replace
  //the background color with one that is trasparent (Alpha=0, R=0, G=0, B=0)
  //to do this we will use a Colormap and use this to define a RemapTable
  ColorMap colorMap = new ColorMap();

  //My watermark was defined with a background of 100% Green this will
  //be the color we search for and replace with transparency
  colorMap.OldColor = Color.FromArgb(255, 0, 255, 0);
  colorMap.NewColor = Color.FromArgb(0, 0, 0, 0);

  ColorMap[] remapTable = {colorMap};

  imageAttributes.SetRemapTable(remapTable, ColorAdjustType.Bitmap);

  //The second color manipulation is used to change the opacity of the
  //watermark.  This is done by applying a 5x5 matrix that contains the
  //coordinates for the RGBA space.  By setting the 3rd row and 3rd column
  //to 0.3f we achive a level of opacity
  float[][] colorMatrixElements = {
           new float[] {1.0f,  0.0f,  0.0f,  0.0f, 0.0f},      
           new float[] {0.0f,  1.0f,  0.0f,  0.0f, 0.0f},       
           new float[] {0.0f,  0.0f,  1.0f,  0.0f, 0.0f},       
           new float[] {0.0f,  0.0f,  0.0f,  0.3f, 0.0f},       
           new float[] {0.0f,  0.0f,  0.0f,  0.0f, 1.0f}};
  ColorMatrix wmColorMatrix = new ColorMatrix(colorMatrixElements);

  imageAttributes.SetColorMatrix(wmColorMatrix, ColorMatrixFlag.Default,
   ColorAdjustType.Bitmap);

  //For this example we will place the watermark in the upper right
  //hand corner of the photograph. offset down 10 pixels and to the
  //left 10 pixles

  int xPosOfWm = ((phWidth - wmWidth)-10);
  int yPosOfWm = 10;

  grWatermark.DrawImage(imgWatermark,
   new Rectangle(xPosOfWm,yPosOfWm,wmWidth,wmHeight),  //Set the detination Position
   0,                  // x-coordinate of the portion of the source image to draw.
   0,                  // y-coordinate of the portion of the source image to draw.
   wmWidth,            // Watermark Width
   wmHeight,      // Watermark Height
   GraphicsUnit.Pixel, // Unit of measurment
   imageAttributes);   //ImageAttributes Object

  //Replace the original photgraphs bitmap with the new Bitmap
  imgPhoto = bmWatermark;
  grPhoto.Dispose();
  grWatermark.Dispose();

  //save new image to file system.
  imgPhoto.Save(WorkingDirectory + ImageName +"_finally.jpg", ImageFormat.Jpeg);
  imgPhoto.Dispose();
  imgWatermark.Dispose();

 }

 private void WriteFontAndImg()
 {  
  
  //create a image object containing the photograph to watermark
  Image imgPhoto = Image.FromFile(WorkingDirectory + ImageName);
  int phWidth = imgPhoto.Width;
  int phHeight = imgPhoto.Height;

  //create a Bitmap the Size of the original photograph
  Bitmap bmPhoto = new Bitmap(phWidth, phHeight, PixelFormat.Format24bppRgb);

  bmPhoto.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);

  //load the Bitmap into a Graphics object
  Graphics grPhoto = Graphics.FromImage(bmPhoto);

  //create a image object containing the watermark
  Image imgWatermark = new Bitmap(WorkingDirectory + ImageWater);
  int wmWidth = imgWatermark.Width;
  int wmHeight = imgWatermark.Height;

  //------------------------------------------------------------
  //Step #1 - Insert Copyright message
  //------------------------------------------------------------

  //Set the rendering quality for this Graphics object
  grPhoto.SmoothingMode = SmoothingMode.AntiAlias;

  //Draws the photo Image object at original size to the graphics object.
  grPhoto.DrawImage(
   imgPhoto,                               // Photo Image object
   new Rectangle(0, 0, phWidth, phHeight), // Rectangle structure
   0,                                      // x-coordinate of the portion of the source image to draw.
   0,                                      // y-coordinate of the portion of the source image to draw.
   phWidth,                                // Width of the portion of the source image to draw.
   phHeight,                               // Height of the portion of the source image to draw.
   GraphicsUnit.Pixel);                    // Units of measure

  //-------------------------------------------------------
  //to maximize the size of the Copyright message we will
  //test multiple Font sizes to determine the largest posible
  //font we can use for the width of the Photograph
  //define an array of point sizes you would like to consider as possiblities
  //-------------------------------------------------------
  int[] sizes = new int[]{16,14,12,10,8,6,4};

  Font crFont = null;
  SizeF crSize = new SizeF();

  //Loop through the defined sizes checking the length of the Copyright string
  //If its length in pixles is less then the image width choose this Font size.
  for (int i=0 ;i<7; i++)
  {
   //set a Font object to Arial (i)pt, Bold
   crFont = new Font("arial", sizes[i], FontStyle.Bold);
   //Measure the Copyright string in this Font
   crSize = grPhoto.MeasureString(FontString, crFont);

   if((ushort)crSize.Width < (ushort)phWidth)
    break;
  }

  //Since all photographs will have varying heights, determine a
  //position 5% from the bottom of the image
  int yPixlesFromBottom = (int)(phHeight *.05);

  //Now that we have a point size use the Copyrights string height
  //to determine a y-coordinate to draw the string of the photograph
  float yPosFromBottom = ((phHeight - yPixlesFromBottom)-(crSize.Height/2));

  //Determine its x-coordinate by calculating the center of the width of the image
  float xCenterOfImg = (phWidth/2);

  //Define the text layout by setting the text alignment to centered
  StringFormat StrFormat = new StringFormat();
  StrFormat.Alignment = StringAlignment.Center;

  //define a Brush which is semi trasparent black (Alpha set to 153)
  SolidBrush semiTransBrush2 = new SolidBrush(Color.FromArgb(153, 0, 0, 0));

  //Draw the Copyright string
  grPhoto.DrawString(FontString,                 //string of text
   crFont,                                   //font
   semiTransBrush2,                           //Brush
   new PointF(xCenterOfImg+1,yPosFromBottom+1),  //Position
   StrFormat);

  //define a Brush which is semi trasparent white (Alpha set to 153)
  SolidBrush semiTransBrush = new SolidBrush(Color.FromArgb(153, 255, 255, 255));

  //Draw the Copyright string a second time to create a shadow effect
  //Make sure to move this text 1 pixel to the right and down 1 pixel
  grPhoto.DrawString(FontString,                 //string of text
   crFont,                                   //font
   semiTransBrush,                           //Brush
   new PointF(xCenterOfImg,yPosFromBottom),  //Position
   StrFormat);                               //Text alignment

  //------------------------------------------------------------
  //Step #2 - Insert Watermark image
  //------------------------------------------------------------

  //Create a Bitmap based on the previously modified photograph Bitmap
  Bitmap bmWatermark = new Bitmap(bmPhoto);
  bmWatermark.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);
  //Load this Bitmap into a new Graphic Object
  Graphics grWatermark = Graphics.FromImage(bmWatermark);

  //To achieve a transulcent watermark we will apply (2) color
  //manipulations by defineing a ImageAttributes object and
  //seting (2) of its properties.
  ImageAttributes imageAttributes = new ImageAttributes();

  //The first step in manipulating the watermark image is to replace
  //the background color with one that is trasparent (Alpha=0, R=0, G=0, B=0)
  //to do this we will use a Colormap and use this to define a RemapTable
  ColorMap colorMap = new ColorMap();

  //My watermark was defined with a background of 100% Green this will
  //be the color we search for and replace with transparency
  colorMap.OldColor = Color.FromArgb(255, 0, 255, 0);
  colorMap.NewColor = Color.FromArgb(0, 0, 0, 0);

  ColorMap[] remapTable = {colorMap};

  imageAttributes.SetRemapTable(remapTable, ColorAdjustType.Bitmap);

  //The second color manipulation is used to change the opacity of the
  //watermark.  This is done by applying a 5x5 matrix that contains the
  //coordinates for the RGBA space.  By setting the 3rd row and 3rd column
  //to 0.3f we achive a level of opacity
  float[][] colorMatrixElements = {
           new float[] {1.0f,  0.0f,  0.0f,  0.0f, 0.0f},      
           new float[] {0.0f,  1.0f,  0.0f,  0.0f, 0.0f},       
           new float[] {0.0f,  0.0f,  1.0f,  0.0f, 0.0f},       
           new float[] {0.0f,  0.0f,  0.0f,  0.3f, 0.0f},       
           new float[] {0.0f,  0.0f,  0.0f,  0.0f, 1.0f}};
  ColorMatrix wmColorMatrix = new ColorMatrix(colorMatrixElements);

  imageAttributes.SetColorMatrix(wmColorMatrix, ColorMatrixFlag.Default,
   ColorAdjustType.Bitmap);

  //For this example we will place the watermark in the upper right
  //hand corner of the photograph. offset down 10 pixels and to the
  //left 10 pixles

  int xPosOfWm = ((phWidth - wmWidth)-10);
  int yPosOfWm = 10;

  grWatermark.DrawImage(imgWatermark,
   new Rectangle(xPosOfWm,yPosOfWm,wmWidth,wmHeight),  //Set the detination Position
   0,                  // x-coordinate of the portion of the source image to draw.
   0,                  // y-coordinate of the portion of the source image to draw.
   wmWidth,            // Watermark Width
   wmHeight,      // Watermark Height
   GraphicsUnit.Pixel, // Unit of measurment
   imageAttributes);   //ImageAttributes Object

  //Replace the original photgraphs bitmap with the new Bitmap
  imgPhoto = bmWatermark;
  grPhoto.Dispose();
  grWatermark.Dispose();

  //save new image to file system.
  imgPhoto.Save(WorkingDirectory + ImageName +"_finally.jpg", ImageFormat.Jpeg);
  imgPhoto.Dispose();
  imgWatermark.Dispose();

       
 }
}

 //水印图片加水印文字
//   ReDrawImg img = new ReDrawImg();
//   img .PublicWorkingDirectory = @"C:/Watermark_src/WaterPic/";
//   img .PublicImageName = "watermark_photo.jpg";
//   img .PublicImageWater = "watermark.bmp";
//   img .PublicFontString = "清清月儿";
//   img .DealImage(); 
  
   //水印文字
   ReDrawImg img = new ReDrawImg();
   img .PublicWorkingDirectory = @"C:/Watermark_src/WaterPic/";
   img .PublicImageName = "watermark_photo.jpg";   
   img .PublicFontString = @"清清月儿";
   img .DealImage();
 

   //水印图片
//   ReDrawImg img = new ReDrawImg();
//   img .PublicWorkingDirectory = @"C:/Watermark_src/WaterPic/";
//   img .PublicImageName = "watermark_photo.jpg";
//   img .PublicImageWater = "watermark.bmp";   
//   img .DealImage(); 
  
 
后台代码：

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class _Default : System.Web.UI.Page
{

    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void bt_upload_Click(object sender, EventArgs e)
    {
        try
        {
            if (FileUpload1.PostedFile.FileName == "")
            {
                this.lb_info.Text = "请选择文件！";
            }
            else
            {
                string filepath = FileUpload1.PostedFile.FileName;
                string filename = filepath.Substring(filepath.LastIndexOf("//") + 1);
                string serverpath1 = Server.MapPath("images/") + filename;
                //string serverpath2 = Server.MapPath("images/") + System.DateTime.Now.ToString("yyy-MM-dd-hh-mm-ss") + Session.SessionID + filename;
                FileUpload1.PostedFile.SaveAs(serverpath1);
                //ImageThumbnail img = new ImageThumbnail(filepath);
                //img.ReducedImage(0.4, serverpath2);
                DrawImg img = new DrawImg();
                img.PublicWorkingDirectory = Server.MapPath("images/");
                img.PublicImageName = filename;
                img.PublicFontString = "http://blog.csdn.net/21aspnet";
                img.PublicImageWater = "yyy.jpg";
                img.DealImage();
                this.lb_info.Text = "上传成功！";
            }
        }
        catch (Exception error)
        {
            this.lb_info.Text = "上传发生错误！原因：" + error.ToString();
        }
    }

}