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：

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();
    }
  }
}

更多关于c#相关内容感兴趣的读者可查看本站专题：《c#图片操作技巧汇总》、《c#字符串操作技巧总结》及《c#面向对象程序设计入门教程》

希望本文所述对大家c#程序设计有所帮助。