ASP.NET2.0打通文件图片处理任督二脉

    // 方法1，按大小
    public bool ReducedImage(int Width, int Height, string targetFilePath)
    {
        try
        {
            Image ReducedImage;
            Image.GetThumbnailImageAbort callb = new Image.GetThumbnailImageAbort(ThumbnailCallback);
            ReducedImage = ResourceImage.GetThumbnailImage(Width, Height, callb, IntPtr.Zero);
            ReducedImage.Save(@targetFilePath, ImageFormat.Jpeg);
            ReducedImage.Dispose();
            return true;
        }
        catch (Exception e)
        {
            ErrorMessage = e.Message;
            return false;
        }
    }

    // 方法2，按百分比  缩小60% Percent为0.6 targetFilePath为目标路径
    public bool ReducedImage(double Percent, string targetFilePath)
    {
        try
        {
            Image ReducedImage;
            Image.GetThumbnailImageAbort callb = new Image.GetThumbnailImageAbort(ThumbnailCallback);
            ImageWidth = Convert.ToInt32(ResourceImage.Width * Percent);
            ImageHeight = (ResourceImage.Height)*ImageWidth/ ResourceImage.Width;//等比例缩放
            ReducedImage = ResourceImage.GetThumbnailImage(ImageWidth, ImageHeight, callb, IntPtr.Zero);
            ReducedImage.Save(@targetFilePath, ImageFormat.Jpeg);
            ReducedImage.Dispose();
            return true;
        }
        catch (Exception e)
        {
            ErrorMessage = e.Message;
            return false;
        }
    }

}

后台代码：
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class _Default : System.Web.UI.Page
{

    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void bt_upload_Click(object sender, EventArgs e)
    {
        try
        {
            if (FileUpload1.PostedFile.FileName == "")
            {
                this.lb_info.Text = "请选择文件！";
            }
            else
            {
                string filepath = FileUpload1.PostedFile.FileName;
                string filename = filepath.Substring(filepath.LastIndexOf("\\") + 1);
                string serverpath1 = Server.MapPath("images/") + filename;
                string serverpath2 = Server.MapPath("images/") + System.DateTime.Now.ToString("yyy-MM-dd-hh-mm-ss") + Session.SessionID + filename;
                FileUpload1.PostedFile.SaveAs(serverpath1);
                ImageThumbnail img = new ImageThumbnail(filepath);
                img.ReducedImage(0.4, serverpath2);//0.4表示缩小40%
                this.lb_info.Text = "上传成功！";
            }
        }
        catch (Exception error)
        {
            this.lb_info.Text = "上传发生错误！原因：" + error.ToString();
        }
    }

}

8.上传图片加水印(文字水印，图片水印，文字+图片水印)

效果图：
原图

水印

给图片加水印以后（注意右上角+正下方）

代码：
DrawImg.cs  出自http://www.codeproject.com/csharp/watermark.asp
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;
public class DrawImg
{
 private string  WorkingDirectory = string.Empty ; //路径
 private string  ImageName = string.Empty;   //被处理的图片
 private string  ImageWater = string.Empty;  //水印图片
 private string  FontString = string.Empty;  //水印文字
 

 enum DealType{NONE,WaterImage,WaterFont,DoubleDo}; //枚举命令

 private DealType dealtype;
 

 public DrawImg()
 {}

 public string PublicWorkingDirectory
 {
  get
  {
   return WorkingDirectory;
  }
  set
  {
   WorkingDirectory = value;
  }
 }

 public string PublicImageName
 {
  get
  {
   return ImageName;
  }
  set
  {
   ImageName = value;
  }
 }

 public string PublicImageWater
 {
  get
  {
   return ImageWater;
  }
  set  //设置了水印图片的话说明是要水印图片效果的
  {
   dealtype = DealType.WaterImage;
   ImageWater = value;
  }
 }

 public string PublicFontString
 {
  get
  {
   return FontString;
  }
  set //设置了水印文字的话说明是要水印文字效果的
  {
   dealtype = DealType.WaterFont;
   FontString = value;
  }
 }

 public void DealImage()
 {
  IsDouble();

  switch( dealtype )
  {
   case DealType.WaterFont: WriteFont(); break;
   case DealType.WaterImage: WriteImg(); break;
   case DealType.DoubleDo: WriteFontAndImg(); break;
  }

 }

 private void IsDouble()
 {
  if(ImageWater+""!="" && FontString+""!="")
  {
            dealtype = DealType.DoubleDo;
  }
 }

 private void WriteFont()
 {
  //set a working directory
  //string WorkingDirectory = @"C:\Watermark_src\WaterPic";

  //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 + ImageName);
  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);

  //------------------------------------------------------------
  //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);

   crFont = new Font("arial",sizes[i],FontStyle.Bold);

   //Measure the Copyright string in this Font
   crSize = grPhoto.MeasureString(FontString, 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(FontString,                 //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(FontString,                 //string of text
   crFont,                                   //font
   semiTransBrush,                           //Brush
   new PointF(xCenterOfImg,yPosFromBottom),  //Position
   StrFormat);   
  
  imgPhoto = bmPhoto;
  grPhoto.Dispose();

  //save new image to file system.
  imgPhoto.Save(WorkingDirectory + ImageName + "_finally.jpg", ImageFormat.Jpeg);
  imgPhoto.Dispose();
  
  //Text alignment
 }

 private void WriteImg()
 {
  //set a working directory
  //string WorkingDirectory = @"C:\Watermark_src\WaterPic";

  //create a image object containing the photograph to watermark
  Image imgPhoto = Image.FromFile(WorkingDirectory + ImageName);
  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 + ImageWater);
  int wmWidth = imgWatermark.Width;
  int wmHeight = imgWatermark.Height;

  //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

  //------------------------------------------------------------
  //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 + ImageName +"_finally.jpg", ImageFormat.Jpeg);
  imgPhoto.Dispose();
  imgWatermark.Dispose();

 }

 private void WriteFontAndImg()
 {  
  
  //create a image object containing the photograph to watermark
  Image imgPhoto = Image.FromFile(WorkingDirectory + ImageName);
  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 + ImageWater);
  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(FontString, 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(FontString,                 //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(FontString,                 //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 + ImageName +"_finally.jpg", ImageFormat.Jpeg);
  imgPhoto.Dispose();
  imgWatermark.Dispose();

       
 }
}

 //水印图片加水印文字
//   ReDrawImg img = new ReDrawImg();
//   img .PublicWorkingDirectory = @"C:\Watermark_src\WaterPic\";
//   img .PublicImageName = "watermark_photo.jpg";
//   img .PublicImageWater = "watermark.bmp";
//   img .PublicFontString = "清清月儿";
//   img .DealImage(); 
  
   //水印文字
   ReDrawImg img = new ReDrawImg();
   img .PublicWorkingDirectory = @"C:\Watermark_src\WaterPic\";
   img .PublicImageName = "watermark_photo.jpg";   
   img .PublicFontString = @"清清月儿";
   img .DealImage();
 

   //水印图片
//   ReDrawImg img = new ReDrawImg();
//   img .PublicWorkingDirectory = @"C:\Watermark_src\WaterPic\";
//   img .PublicImageName = "watermark_photo.jpg";
//   img .PublicImageWater = "watermark.bmp";   
//   img .DealImage(); 
  
 
后台代码：

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class _Default : System.Web.UI.Page
{

    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void bt_upload_Click(object sender, EventArgs e)
    {
        try
        {
            if (FileUpload1.PostedFile.FileName == "")
            {
                this.lb_info.Text = "请选择文件！";
            }
            else
            {
                string filepath = FileUpload1.PostedFile.FileName;
                string filename = filepath.Substring(filepath.LastIndexOf("\\") + 1);
                string serverpath1 = Server.MapPath("images/") + filename;
                //string serverpath2 = Server.MapPath("images/") + System.DateTime.Now.ToString("yyy-MM-dd-hh-mm-ss") + Session.SessionID + filename;
                FileUpload1.PostedFile.SaveAs(serverpath1);
                //ImageThumbnail img = new ImageThumbnail(filepath);
                //img.ReducedImage(0.4, serverpath2);
                DrawImg img = new DrawImg();
                img.PublicWorkingDirectory = Server.MapPath("images/");
                img.PublicImageName = filename;
                img.PublicFontString = "http://blog.csdn.net/21aspnet";
                img.PublicImageWater = "yyy.jpg";
                img.DealImage();
                this.lb_info.Text = "上传成功！";
            }
        }
        catch (Exception error)
        {
            this.lb_info.Text = "上传发生错误！原因：" + error.ToString();
        }
    }

}