给图片添加水印效果

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

/**//// <summary>
        /// 用于处理图片
        /// 给图片加入水印
        /// </summary>
        /// <param name="Copyright">需要写入的版权信息</param>
        /// <param name="MarkBmpPath">需要假如的logo图片</param>
        /// <param name="photoPath">需要处理的图片的路径</param>
        /// <param name="savePhotoPath">保存的图片路径</param>
        public void MakeWatermark(string Copyright,string MarkBmpPath,string photoPath,string savePhotoPath)
        {

            //创建一个image对象,即要被处理的图片
            Image imgPhoto = Image.FromFile(photoPath);
            int phWidth = imgPhoto.Width;
            int phHeight = imgPhoto.Height;

            //创建原始图片大小的Bitmap
            Bitmap bmPhoto = new Bitmap(phWidth, phHeight, PixelFormat.Format24bppRgb);

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

            //将位图bmPhoto加载到Graphics对象
            Graphics grPhoto = Graphics.FromImage(bmPhoto);

            //创建一个需要填充水银的Image对象
            Image imgWatermark = new Bitmap(MarkBmpPath);
            int wmWidth = imgWatermark.Width;
            int wmHeight = imgWatermark.Height;

            //------------------------------------------------------------
            //第一步,插入版权信息
            //------------------------------------------------------------

            //设置图象的成相质量
            grPhoto.SmoothingMode = SmoothingMode.AntiAlias;

            //将原始图象绘制到grPhoto上
            grPhoto.DrawImage(
                imgPhoto,                               // 要绘制的Image对象
                new Rectangle(0, 0, phWidth, phHeight), // 绘制图象的位置和大小
                0,                                      // 要绘制的原图象部分的左上角的X坐标
                0,                                      // 要绘制的原图象部分的左上角的Y坐标
                phWidth,                                // 要绘制的原图象的高度
                phHeight,                               // 要绘制的原图象的宽度
                GraphicsUnit.Pixel);                    // 源矩形的度量单位

            //-------------------------------------------------------
            //字体大小放在一个数组中,最大字体为32.
            //感觉用处不大,可以自己再修改这里
            //-------------------------------------------------------
            int[] sizes = new int[]{32,14,12,10,8,6,4};

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

            //循环测试数组中所定义的字体大小是否适合版权信息,如果合适就使用此种字体大小
            for (int i=0 ;i<6; i++)
            {
                //设置字体类型,可以单独提出,作为参数
                crFont = new Font("迷你繁篆书", sizes[0], FontStyle.Bold);
                //测量此种字体大小
                crSize = grPhoto.MeasureString(Copyright, crFont);

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

            //给底部保留%3的空间
            int yPixlesFromBottom = (int)(phHeight *.03);

            //设置字体在图片中的位置
            float yPosFromBottom = ((phHeight - yPixlesFromBottom)-(crSize.Height/2));

            //float xCenterOfImg = (phWidth/2);
            float xCenterOfImg = (phWidth-(crSize.Width)/2);
            //设置字体居中
            StringFormat StrFormat = new StringFormat();
            StrFormat.Alignment = StringAlignment.Center;
            
            //设置绘制文本的颜色和纹理 (Alpha=153)
            SolidBrush semiTransBrush2 = new SolidBrush(Color.FromArgb(153, 0, 0, 0));

            //将版权信息绘制到图象上
            grPhoto.DrawString(Copyright,                     //版权信息
                crFont,                                       //字体
                semiTransBrush2,                              //绘制文本的颜色及纹理
                new PointF(xCenterOfImg+1,yPosFromBottom+1),  //绘制文本的位置
                StrFormat);                                   //格式

            //设置绘制文本的颜色和纹理 (Alpha=153)
            SolidBrush semiTransBrush = new SolidBrush(Color.FromArgb(153, 255, 255, 255));

            //重新绘制版权信息,以让其具有阴影效果
            //将文本向又下移动一个象素
            grPhoto.DrawString(Copyright,                 //版权信息
                crFont,                                   //字体
                semiTransBrush,                           //绘制文本的颜色及纹理
                new PointF(xCenterOfImg,yPosFromBottom),  //绘制文本的位置
                StrFormat);                               //格式

            

            //------------------------------------------------------------
            //第二步,插入图片水印
            //------------------------------------------------------------

            //在原来修改过的bmPhoto上创建一个水银位图
            Bitmap bmWatermark = new Bitmap(bmPhoto);

            bmWatermark.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);
            //将位图bmWatermark加载到Graphics对象
            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(savePhotoPath, ImageFormat.Jpeg);
            imgPhoto.Dispose();
            imgWatermark.Dispose();

        }
    }
}