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 Settingsadministrator.JAZZMINEMy DocumentsProjectsTutorialsWaterMark"; //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(); } } }

希望本文所述对大家C#程序设计有所帮助。