C#实现给图片加水印的方法

本文实例讲述了C#实现给图片加水印的方法。分享给大家供大家参考，具体如下：
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									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();

									    }

									  }

									}