c#图片添加水印的实例代码

using system;
using system.drawing;
using system.drawing.drawing2d;
using system.drawing.imaging;
using system.io;
namespace imagedrawing
{
 /// <summary>
 /// 图片修改类,主要是用来保护图片版权的
 /// </summary>
 public class imagemodification
 {
  #region "member fields"
  private string modifyimagepath=null;
  private string drawedimagepath=null;
  private int rightspace;
  private int bottoamspace;
  private int lucencypercent=70;
  private string outpath=null;
  #endregion
  public imagemodification()
  {
  }
  #region "propertys"
  /// <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;}
  }
  //获取或设置水印在修改图片中距底部的高度
  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 "methods"
  /// <summary>
  /// 开始绘制水印
  /// </summary>
  public void drawimage()
  {
   image modifyimage=null;
   image drawedimage=null;
   graphics g=null;
   try
   {   
    //建立图形对象
    modifyimage=image.fromfile(this.modifyimagepath);
    drawedimage=image.fromfile(this.drawedimagepath);
    g=graphics.fromimage(modifyimage);
    //获取要绘制图形坐标
    int x=modifyimage.width-this.rightspace;
    int y=modifyimage.height-this.bottoamspace;
    //设置颜色矩阵
    float[][] matrixitems ={
             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);
    //绘制阴影图像
    g.drawimage(
     drawedimage,
     new rectangle(x,y,drawedimage.width,drawedimage.height),
     0,0,drawedimage.width,drawedimage.height,
     graphicsunit.pixel,imgattr);
    //保存文件
    string[] allowimagetype={".jpg",".gif",".png",".bmp",".tiff",".wmf",".ico"};
    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
 }
}