GDI_图片半透明效果示例

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();

}

}

}