产生随机验证图片代码来自CNBlogsDottext10Beta2

调用方式，新建以后缀名为*.ashx的文件，然后再里面写入以下代码：

<%@ WebHandler Language="C#" Class="ViliDateImage" %>

using System;

using System.Web;

using System.Drawing.Imaging;

public class ViliDateImage : IHttpHandler {

public void ProcessRequest (HttpContext context)

{

context.Response.ContentType = "image/jpeg";

using(CaptchaImage ci = new CaptchaImage(CaptchaImage.GenerateRandomCode(),156,40))

{

ci.Image.Save(context.Response.OutputStream,ImageFormat.Jpeg);

}

}

public bool IsReusable {

get {

return false;

}

}

}

using System;

using System.Drawing;

using System.Drawing.Drawing2D;

using System.Drawing.Imaging;

using System.Drawing.Text;

/// <summary>

/// 产生随机验证图片。

/// 代码来自CNBlogsDottext10Beta2。

/// http://scottwater.com/
/// http://www.cnblogs.com/
/// </summary>

public class CaptchaImage : IDisposable

{

// Public properties (all read-only).

public string Text

{

get { return this.text; }

}

public Bitmap Image

{

get { return this.image; }

}

public int Width

{

get { return this.width; }

}

public int Height

{

get { return this.height; }

}

// Internal properties.

private string text;

private int width;

private int height;

private string familyName = "黑体";

private Bitmap image;

// For generating random numbers.

private Random random = new Random();

// ====================================================================

// Initializes a new instance of the CaptchaImage class using the

// specified text, width and height.

// ====================================================================

public CaptchaImage(string s, int width, int height)

{

this.text = s;

this.SetDimensions(width, height);

this.GenerateImage();

}

// ====================================================================

// Initializes a new instance of the CaptchaImage class using the

// specified text, width, height and font family.

// ====================================================================

public CaptchaImage(string s, int width, int height, string familyName)

{

this.text = s;

this.SetDimensions(width, height);

this.SetFamilyName(familyName);

this.GenerateImage();

}

// ====================================================================

// This member overrides Object.Finalize.

// ====================================================================

~CaptchaImage()

{

Dispose(false);

}

// ====================================================================

// Releases all resources used by this object.

// ====================================================================

public void Dispose()

{

GC.SuppressFinalize(this);

this.Dispose(true);

}

// ====================================================================

// Custom Dispose method to clean up unmanaged resources.

// ====================================================================

protected virtual void Dispose(bool disposing)

{

if(disposing)

// Dispose of the bitmap.

this.image.Dispose();

}

// ====================================================================

// Sets the image width and height.

// ====================================================================

private void SetDimensions(int width, int height)

{

// Check the width and height.

if(width <= 0)

throw new ArgumentOutOfRangeException("width", width, "Argument out of range, must be greater than zero.");

if(height <= 0)

throw new ArgumentOutOfRangeException("height", height, "Argument out of range, must be greater than zero.");

this.width = width;

this.height = height;

}

// ====================================================================

// Sets the font used for the image text.

// ====================================================================

private void SetFamilyName(string familyName)

{

// If the named font is not installed, default to a system font.

try

{

Font font = new Font(this.familyName, 12F);

this.familyName = familyName;

font.Dispose();

}

catch

{

this.familyName = System.Drawing.FontFamily.GenericSerif.Name;

}

}

// ====================================================================

// Creates the bitmap image.

// ====================================================================

private void GenerateImage()

{

// Create a new 32-bit bitmap image.

Bitmap bitmap = new Bitmap(this.width, this.height, PixelFormat.Format32bppArgb);

// Create a graphics object for drawing.

Graphics g = Graphics.FromImage(bitmap);

g.SmoothingMode = SmoothingMode.AntiAlias;

Rectangle rect = new Rectangle(0, 0, this.width, this.height);

// Fill in the background.

HatchBrush hatchBrush = new HatchBrush(HatchStyle.SmallConfetti, Color.LightGray, Color.White);

g.FillRectangle(hatchBrush, rect);

// Set up the text font.

SizeF size;

float fontSize = rect.Height + 1;

Font font;

// Adjust the font size until the text fits within the image.

do

{

fontSize--;

font = new Font(this.familyName, fontSize, FontStyle.Bold);

size = g.MeasureString(this.text, font);

} while(size.Width > rect.Width);

// Set up the text format.

StringFormat format = new StringFormat();

format.Alignment = StringAlignment.Center;

format.LineAlignment = StringAlignment.Center;

// Create a path using the text and warp it randomly.

GraphicsPath path = new GraphicsPath();

path.AddString(this.text, font.FontFamily, (int)font.Style, font.Size, rect, format);

float v = 4F;

PointF[] points =

{

new PointF(this.random.Next(rect.Width) / v, this.random.Next(rect.Height) / v),

new PointF(rect.Width - this.random.Next(rect.Width) / v, this.random.Next(rect.Height) / v),

new PointF(this.random.Next(rect.Width) / v, rect.Height - this.random.Next(rect.Height) / v),

new PointF(rect.Width - this.random.Next(rect.Width) / v, rect.Height - this.random.Next(rect.Height) / v)

};

Matrix matrix = new Matrix();

matrix.Translate(0F, 0F);

path.Warp(points, rect, matrix, WarpMode.Perspective, 0F);

// Draw the text.

hatchBrush = new HatchBrush(HatchStyle.LargeConfetti, Color.DarkGray, Color.DarkGray);

g.FillPath(hatchBrush, path);

// Add some random noise.

int m = Math.Max(rect.Width, rect.Height);

for(int i = 0; i < (int)(rect.Width * rect.Height / 30F); i++)

{

int x = this.random.Next(rect.Width);

int y = this.random.Next(rect.Height);

int w = this.random.Next(m / 50);

int h = this.random.Next(m / 50);

g.FillEllipse(hatchBrush, x, y, w, h);

}

// Clean up.

font.Dispose();

hatchBrush.Dispose();

g.Dispose();

// Set the image.

this.image = bitmap;

}

public static string GenerateRandomCode()

{

string s = "";

Random random = new Random();

for(int i = 0; i < 5; i++)

s = String.Concat(s, random.Next(10).ToString());

return s;

}

}