C#实现给图片加水印的方法

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;
namespace Tutorial
{
  class WaterMark
  {
    [STAThread]
    static void Main(string[] args)
    {
      //set a working directory
      string WorkingDirectory = @"C:\Documents and Settings\administrator.JAZZMINE\My Documents\Projects\Tutorials\WaterMark";
      //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 + "\\watermark_photo.jpg");
      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 + "\\watermark.bmp");
      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(Copyright, 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(Copyright, //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(Copyright, //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 + "\\watermark_final.jpg", ImageFormat.Jpeg);
      imgPhoto.Dispose();
      imgWatermark.Dispose();
    }
  }
}