为图片添加水印

利用.net中System.Drawing命名空间下的常用类我们就可以轻松的为图片添加文字水印和图片水印，并且可以自定义水印文字和水印图片的大小、位置、颜色、透明度等等！对于jpg或者png等图片，可以直接通过Graphics g= Graphics.FromImage(image)来获得Graphics对象，但对于gif图片，通过这种方法无法获得Graphics对象，解决这个问题的方法是首先根据.gif文件的大小生成一个位图作图区，然后将原图复制到作图区，做进行处理，以下是水印添加类的完整代码:

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

namespace JillZhang
{
    public enum MarkType
    {
        Text,Image
    }
    /**//// <summary>
    /// 给图片添加水印得类得描述
    /// </summary>
    public class WaterMark
    {
        ---------------------成员变量---------------------#region ---------------------成员变量---------------------        
        private string _text="";
        private string _imgPath="";
        private int _markX=0;
        private int _markY=0;
        private float _transparency=1;
        private string _fontFamily="宋体";
        private Color _textColor=Color.Black;
        private bool _textbold=false;
        int[] sizes=new int[]{48,32,16,8,6,4};
        private Image _image=null;
        private Image _markedIamge=null;
        private MarkType _markType=MarkType.Text;
        #endregion

        ---------------------构造函数---------------------#region ---------------------构造函数---------------------
        /**//// <summary>
        /// 实例化一个水印类
        /// </summary>
        public WaterMark()
        {
            
        }
        /**//// <summary>
        ///　初始化一个只添加文字水印得实例
        /// </summary>
        /// <param name="text">水印文字</param>
        /// <param name="fontFamily">文字字体</param>
        /// <param name="bold">是否粗体</param>
        /// <param name="color">字体颜色</param>
        /// <param name="markX">标记位置横坐标</param>
        /// <param name="markY">标记位置纵坐标</param>
        public WaterMark(string text,string fontFamily,bool bold,Color color,int markX,int markY)
        {    
            this._markType=MarkType.Text;
            this._text=text;
            this._fontFamily=fontFamily;
            this._textbold=bold;
            this._textColor=color;
            this._markX=markX;
            this._markY=MarkY;
            this.Mark();
        }
        /**//// <summary>
        /// 实例化一个只添加图片水印得实例
        /// </summary>
        /// <param name="imagePath">水印图片路径</param>
        /// <param name="tranparence">透明度</param>
        /// <param name="markX">标记位置横坐标</param>
        /// <param name="markY">标记位置纵坐标</param>
        public WaterMark(string imagePath,float tranparence,int markX,int markY)
        {
            this._markType=MarkType.Image;        
            this._imgPath=imagePath;
            this._markX=markX;
            this._markY=MarkY;
            this._transparency=tranparence;
            this.Mark();
        }
        #endregion

        ---------------------公共属性---------------------#region ---------------------公共属性---------------------
        /**//// <summary>
        /// 水印类型
        /// </summary>
        public MarkType WaterMarkType
        {
            get
            {
                return _markType;
            }
            set
            {
                _markType=value;
            }
        }        
        /**//// <summary>
        /// 文字水印得内容
        /// </summary>
        public string Text
        {
            get{return _text;}
            set{_text=value;}
        }
        /**//// <summary>
        /// 水印图片得路径
        /// </summary>
        public string WaterImagePath
        {
            get
            {
                return _imgPath;
            }
            set
            {
                this._imgPath=value;
            }
        }
        /**//// <summary>
        /// 水印图片
        /// </summary>
        public Image WaterImage
        {
            get
            {
                try
                {
                    return Image.FromFile(this.WaterImagePath);
                }
                catch
                {
                    return null;
                }
                }            
        }
        /**//// <summary>
        /// 添加水印位置得横坐标
        /// </summary>
        public int MarkX
        {
            get{return _markX;}
            set{_markX=value;}
        }
        /**//// <summary>
        /// 添加水印位置得纵坐标
        /// </summary>
        public int MarkY
        {
            get{return _markY;}
            set{_markY=value;}
        }
        /**//// <summary>
        /// 水印得透明度
        /// </summary>
        public float Transparency
        {
            get
            {
                if(_transparency>1.0f)
                {
                    _transparency=1.0f;
                }
                return _transparency;}
            set{_transparency=value;}
        }
        /**//// <summary>
        /// 水印文字得颜色
        /// </summary>
        public Color TextColor
        {
            get{return _textColor;}
            set{_textColor=value;}
        }
        /**//// <summary>
        /// 水印文字得字体
        /// </summary>
        public string TextFontFamilyStr
        {
            get{return _fontFamily;}
            set{_fontFamily=value;}
        }
        public FontFamily TextFontFamily
        {
            get{return new FontFamily(this.TextFontFamilyStr);}
        }
        /**//// <summary>
        /// 水印文字是否加粗
        /// </summary>
        public bool Bold
        {
            get{return _textbold;}
            set{_textbold=value;}
        }
        /**//// <summary>
        /// 原图
        /// </summary>
    　　public Image SourceImage
      {
          get
          {
              return _image;
          }
          set
          {
              _image=value;
          }
      }
        /**//// <summary>
        /// 加过水印之后得图
        /// </summary>
        public Image MarkedImage
        {
            get
            {
                return this._markedIamge;
            }            
        }

        #endregion

        ---------------------方法事件---------------------#region ---------------------方法事件---------------------
        public Image Mark(Image img,MarkType markType,string text,Image waterImg,int markx,int marky,
            bool bold,Color textColor,float transparence,FontFamily fontFamily)
        {
            //首先先判断该图片是否是 gif动画，如果为gif动画不对图片进行改动
        
            foreach(Guid guid in img.FrameDimensionsList)
            {
                FrameDimension dimension= new FrameDimension(guid);
                if(img.GetFrameCount(dimension)>1)
                {
                    return img;
                }
            }
            try
            {
                //添加文字水印
                if(markType==MarkType.Text)
                {
                    //根据源图片生成新的Bitmap对象作为作图区，为了给gif图片添加水印，才有此周折
                    Bitmap newBitmap=new Bitmap(img.Width,img.Height,PixelFormat.Format24bppRgb); 
                    //设置新建位图得分辨率
                    newBitmap.SetResolution(img.HorizontalResolution,img.VerticalResolution);
                    //创建Graphics对象，以对该位图进行操作
                    Graphics g = Graphics.FromImage(newBitmap);
                    //消除锯齿
                    g.SmoothingMode=SmoothingMode.AntiAlias;
                    //将原图拷贝到作图区
                    g.DrawImage(img,new Rectangle(0,0,img.Width,img.Height),0,0,img.Width,img.Height,GraphicsUnit.Pixel);
                    //声明字体对象
                    Font cFont = null;
                    //用来测试水印文本长度得尺子
                    SizeF size=new SizeF();
                    //探测出一个适合图片大小得字体大小，以适应水印文字大小得自适应
                    for(int i=0;i<6;i++)
                    {
                        //创建一个字体对象
                        cFont= new Font(fontFamily,sizes[i]);
                        //是否加粗
                        if(!bold)
                        {
                            cFont= new Font(fontFamily,sizes[i],FontStyle.Regular);
                        }
                        else
                        {
                            cFont=new Font(fontFamily,sizes[i],FontStyle.Bold);
                        }
                        //测量文本大小
                        size=g.MeasureString(this.Text,cFont);
                        //匹配第一个符合要求得字体大小
                        if((ushort)size.Width<(ushort)img.Width)
                        {
                            break;
                        }
                    }
                    //创建刷子对象，准备给图片写上文字
                    Brush brush= new SolidBrush(textColor);
                    //在指定得位置写上文字
                    g.DrawString(text,cFont,brush,markx,marky);
                    //释放Graphics对象
                    g.Dispose();   
                    //将生成得图片读入MemoryStream
                    System.IO.MemoryStream ms = new System.IO.MemoryStream();
                    newBitmap.Save(ms,ImageFormat.Jpeg);
                    //重新生成Image对象
                    img=System.Drawing.Image.FromStream(ms);    
                    //返回新的Image对象
                    return img;

                }
                //添加图像水印
                else if(markType==MarkType.Image)
                {
                    //获得水印图像
                    Image markImg = waterImg;
                    //创建颜色矩阵
                    float[][] ptsArray ={ 
                                            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, transparence, 0}, //注意：此处为0.0f为完全透明，1.0f为完全不透明
                                            new float[] {0, 0, 0, 0, 1}}; 
                    ColorMatrix colorMatrix= new ColorMatrix(ptsArray);
                    //新建一个Image属性
                    ImageAttributes imageAttributes= new ImageAttributes();
                    //将颜色矩阵添加到属性
                    imageAttributes.SetColorMatrix(colorMatrix,ColorMatrixFlag.Default,
                        ColorAdjustType.Default);
                    //生成位图作图区
                    Bitmap newBitmap=new Bitmap(img.Width,img.Height,PixelFormat.Format24bppRgb);
                    //设置分辨率
                    newBitmap.SetResolution(img.HorizontalResolution,img.VerticalResolution);
                    //创建Graphics
                    Graphics g = Graphics.FromImage(newBitmap);
                    //消除锯齿
                    g.SmoothingMode=SmoothingMode.AntiAlias;
                    //拷贝原图到作图区
                    g.DrawImage(img,new Rectangle(0,0,img.Width,img.Height),0,0,img.Width,img.Height,GraphicsUnit.Pixel);
                    //如果原图过小
                    if(markImg.Width>img.Width||markImg.Height>img.Height)
                    {
                        System.Drawing.Image.GetThumbnailImageAbort callb=null;
                        //对水印图片生成缩略图,缩小到原图得1/4
                        System.Drawing.Image new_img=markImg.GetThumbnailImage(img.Width/4,markImg.Height*img.Width/markImg.Width,callb,new System.IntPtr());
                        //添加水印
                        g.DrawImage(new_img,new Rectangle(markx,marky,new_img.Width,new_img.Height),0,0,new_img.Width,new_img.Height,GraphicsUnit.Pixel,imageAttributes);
                        //释放缩略图
                        new_img.Dispose();
                        //释放Graphics
                        g.Dispose();
                        //将生成得图片读入MemoryStream
                        System.IO.MemoryStream ms = new System.IO.MemoryStream();
                        newBitmap.Save(ms,ImageFormat.Jpeg);
　　　　　　　　　　//返回新的Image对象
                        img=Image.FromStream(ms);
                        return img;
                    }
                        //原图足够大
                    else
                    {
                        //添加水印
                        g.DrawImage(markImg,new Rectangle(markx,marky,markImg.Width,markImg.Height),0,0,markImg.Width,markImg.Height,GraphicsUnit.Pixel,imageAttributes);
                        //释放Graphics
                        g.Dispose();
                        //将生成得图片读入MemoryStream
                        System.IO.MemoryStream ms = new System.IO.MemoryStream();
                        newBitmap.Save(ms,ImageFormat.Jpeg);
                        //返回新的Image对象
                        img=Image.FromStream(ms);
                        return img;
                    }                    
                }
                return img;
            }
            catch
            {
                return img;   
            }            

        }
        /**//// <summary>
        /// 添加水印，此方法适用于gif格式得图片
        /// </summary>
        /// <param name="image">需要添加水印得图片</param>
        /// <returns>添加水印之后得图片</returns>
        private void Mark()
        {
            this._markedIamge=Mark(this.SourceImage,this.WaterMarkType,this._text,this.WaterImage,this._markX,this._markY,this._textbold,this._textColor,this._transparency,this.TextFontFamily);
        }
        #endregion        
    }
}

利用该类，您可以轻松的对图片加水印，但也有不足，通过这种方法添加水印，会破坏.gif动画，因为我目前还不知道如何判断.gif文件是否是动画，这个问题还需要各位网友的建议和帮助