C#.NET 添加图片水印

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;

namespace Pub.Class
{
    /// <summary>
    /// 添加水印类 只支持添加图片水印
    /// </summary>
 public class Watermark
    {
        #region 私有成员
        private string modifyImagePath=null;
  private string drawedImagePath=null;
  private int rightSpace;
  private int bottoamSpace;
  private int lucencyPercent=70;
  private string outPath=null;
        #endregion

        #region 构造器
        /// <summary>
        /// 构造函数
        /// </summary>
        public Watermark() { }
        #endregion

        #region 属性
        /// <summary>
  /// 获取或设置要修改的图像路径
  /// </summary>
  public string ModifyImagePath
  {
   get{return this.modifyImagePath;}
   set{this.modifyImagePath=value;}
  }
  /// <summary>
  /// 获取或设置在画的图片路径(水印图片)
  /// </summary>
  public string DrawedImagePath
  {
   get{return this.drawedImagePath;}
   set{this.drawedImagePath=value;}
  }
  /// <summary>
  /// 获取或设置水印在修改图片中的右边距
  /// </summary>
  public int RightSpace
  {
   get{return this.rightSpace;}
   set{this.rightSpace=value;}
  }
  /// <summary>
        /// 获取或设置水印在修改图片中距底部的高度
  /// </summary>
  public int BottoamSpace
  {
   get{return this.bottoamSpace;}
   set{this.bottoamSpace=value;}
  }
  /// <summary>
  /// 获取或设置要绘制水印的透明度,注意是原来图片透明度的百分比
  /// </summary>
  public int LucencyPercent
  {
   get{return this.lucencyPercent;}
   set { if(value>=0&&value<=100) this.lucencyPercent=value; }
  }
  /// <summary>
  /// 获取或设置要输出图像的路径
  /// </summary>
  public string OutPath
  {
   get{return this.outPath;}
   set{this.outPath=value;}
        }
        #endregion

        #region 开始绘制水印 DrawImage
        /// <summary>
  /// 开始绘制水印
  /// </summary>
        /// <example>
        /// <code>
        ///     Watermark wm = new Watermark();
        ///     wm.DrawedImagePath= Server.MapPath("") + "/upfile/" + "backlogo.gif";
        ///     wm.ModifyImagePath=path;
        ///     wm.RightSpace=184;
        ///     wm.BottoamSpace=81;
        ///     wm.LucencyPercent=50;
        ///     wm.OutPath=Server.MapPath("") + "/upfile/" + fileName + "_new" + extension;
        ///     wm.DrawImage();
        ///
        ///     //保存加水印过后的图片,删除原始图片
        ///     mFileName=fileName + "_new" + extension;
        ///     if(File.Exists(path)) {  File.Delete(path); }
        /// </code>
        /// </example>
  public void DrawImage()
  {
   Image modifyImage=null;
   Image drawedImage=null;
   Graphics g=null;
   try {
    modifyImage=Image.FromFile(this.ModifyImagePath);//建立图形对象
    drawedImage=Image.FromFile(this.DrawedImagePath);
    g=Graphics.FromImage(modifyImage);

    int x=modifyImage.Width-this.rightSpace;//获取要绘制图形坐标
    int y=modifyImage.Height-this.BottoamSpace;

    float[][] matrixItems ={//设置颜色矩阵
            new float[] {1, 0, 0, 0, 0},
            new float[] {0, 1, 0, 0, 0},
            new float[] {0, 0, 1, 0, 0},
            new float[] {0, 0, 0, (float)this.LucencyPercent/100f, 0},
            new float[] {0, 0, 0, 0, 1}}; 

    ColorMatrix colorMatrix = new ColorMatrix(matrixItems);
    ImageAttributes imgAttr=new ImageAttributes();
    imgAttr.SetColorMatrix(colorMatrix,ColorMatrixFlag.Default,ColorAdjustType.Bitmap);

    g.DrawImage(//绘制阴影图像
     drawedImage,
     new Rectangle(x,y,drawedImage.Width,drawedImage.Height),
     0,0,drawedImage.Width,drawedImage.Height,
     GraphicsUnit.Pixel,imgAttr);

    string[] allowImageType={".jpg",".gif",".png",".bmp",".tiff",".wmf",".ico"};//保存文件
    FileInfo file=new FileInfo(this.ModifyImagePath);
    ImageFormat imageType=ImageFormat.Gif;
    switch(file.Extension.ToLower()) {
     case ".jpg": imageType=ImageFormat.Jpeg; break;
     case ".gif": imageType=ImageFormat.Gif; break;
     case ".png": imageType=ImageFormat.Png; break;
     case ".bmp": imageType=ImageFormat.Bmp; break;
     case ".tif": imageType=ImageFormat.Tiff; break;
     case ".wmf": imageType=ImageFormat.Wmf; break;
     case ".ico": imageType=ImageFormat.Icon; break;
     default: break;
    }
    MemoryStream ms=new MemoryStream();
    modifyImage.Save(ms,imageType);
    byte[] imgData=ms.ToArray();
    modifyImage.Dispose();
    drawedImage.Dispose();
    g.Dispose();
    FileStream fs=null;
    if(this.OutPath==null || this.OutPath=="") {
     File.Delete(this.ModifyImagePath);
     fs=new FileStream(this.ModifyImagePath,FileMode.Create,FileAccess.Write);
    } else {
     fs=new FileStream(this.OutPath,FileMode.Create,FileAccess.Write);
    }
    if(fs!=null) {
     fs.Write(imgData,0,imgData.Length);
     fs.Close();
    }
   } finally {
    try {
     drawedImage.Dispose();
     modifyImage.Dispose();
     g.Dispose();
    } catch{}
   }
  }
        #endregion
    }
}

转自：http://www.cnblogs.com/livexy/archive/2010/07/05/1771714.html