在开发B/S结构的应用程序时，登录时为了防止恶意操作，经常要用到验证码，类似的验证码在网上搜一下有很多，无非就是生成一个带有文字的图片，在这里，发布一个类似于google所用的验证码，给大家多一种选择。
效果如图： 
代码如下：
using System;
using System.Text;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
namespace Mirainsoft.ValidateCode
{
/// <summary>
/// 验证码处理类
/// </summary>
public class ValidateCodeFactory
{
/// <summary>
/// 字体选择范围数组
/// </summary>
private string[] fonts = { "Times New Roman", "Georgia", "Arial", "Comic Sans MS" };
/// <summary>
/// 验证码取值范围数组
/// </summary>
private string[] CodeScopes = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" };
///// <summary>
///// 颜色取值范围数组
///// </summary>
//private Color[] ColorScopes = { Color.Crimson, Color.PaleVioletRed, Color.MediumVioletRed, Color.Purple, Color.DarkViolet, Color.Indigo, Color.SlateBlue, Color.DarkSlateBlue, Color.MediumBlue, Color.DarkBlue, Color.SlateBlue, Color.DarkCyan, Color.Gold, Color.Goldenrod, Color.Orange, Color.OrangeRed, Color.Red, Color.DarkRed};
/// <summary>
/// 随机数
/// </summary>
private Random rand;
/// <summary>
/// 随机数种子
/// </summary>
private int randseed;
private string text;
private int width;
private int height;
private string familyName;
private Bitmap image;
/// <summary>
/// 显示文本
/// </summary>
public string Text
{
get { return this.text; }
}
/// <summary>
/// 生成的位图对像
/// </summary>
public Bitmap Image
{
get { return this.image; }
}
/// <summary>
/// 验证码宽度
/// </summary>
public int Width
{
get { return this.width; }
}
/// <summary>
/// 验证码高度
/// </summary>
public int Height
{
get { return this.height; }
}
/// <summary>
/// 验证码处理类
/// </summary>
/// <param name="length">显示文本长度,随机生成</param>
/// <param name="width">验证码宽度</param>
/// <param name="height">验证码高度</param>
public ValidateCodeFactory(int length, int width, int height)
{
this.randseed = 111;
for (int i=0;i<length;i++)
this.text = string.Concat(this.text, CodeScopes[Next(CodeScopes.Length)]);
this.SetDimensions(width, height);
this.SetFamilyName(this.fonts[Next(this.fonts.Length)]);
this.GenerateImage();
}
/// <summary>
/// 验证码处理类
/// </summary>
/// <param name="s">显示文本</param>
/// <param name="width">验证码宽度</param>
/// <param name="height">验证码高度</param>
public ValidateCodeFactory(string s, int width, int height)
{
this.randseed = 111;
this.text = s;
this.SetDimensions(width, height);
this.SetFamilyName(this.fonts[Next(this.fonts.Length)]);
this.GenerateImage();
}
/// <summary>
/// 验证码处理类
/// </summary>
/// <param name="s">显示文本</param>
/// <param name="width">验证码宽度</param>
/// <param name="height">验证码高度</param>
/// <param name="familyName">字体名称</param>
public ValidateCodeFactory(string s, int width, int height, string familyName)
{
this.randseed = 111;
this.text = s;
this.SetDimensions(width, height);
this.SetFamilyName(familyName);
this.GenerateImage();
}
/// <summary>
/// 垃圾回收
/// </summary>
~ValidateCodeFactory()
{
Dispose(false);
}
/// <summary>
/// 释放资源
/// </summary>
public void Dispose()
{
GC.SuppressFinalize(this);
this.Dispose(true);
}
/// <summary>
/// 释放资源
/// </summary>
/// <param name="disposing">是否回收</param>
protected virtual void Dispose(bool disposing)
{
if (disposing)
// Dispose of the bitmap.
this.image.Dispose();
}
/// <summary>
/// 设置验证码的宽度和高度
/// </summary>
/// <param name="width">验证码宽度</param>
/// <param name="height">验证码高度</param>
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;
}
/// <summary>
/// 设置显示文本的字体
/// </summary>
/// <param name="familyName">字体名称</param>
private void SetFamilyName(string familyName)
{
try
{
Font font = new Font(this.familyName, 12F);
this.familyName = familyName;
font.Dispose();
}
catch
{
this.familyName = System.Drawing.FontFamily.GenericSerif.Name;
}
}
/// <summary>
/// 生成验证码
/// </summary>
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 / 4f )* 3f > 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(Next(rect.Width) / v, Next(rect.Height) / v),
new PointF(rect.Width - Next(rect.Width) / v, Next(rect.Height) / v),
new PointF(Next(rect.Width) / v, rect.Height - Next(rect.Height) / v),
new PointF(rect.Width - Next(rect.Width) / v, rect.Height - 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.Gray, Color.Gray);
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 = Next(rect.Width);
int y = Next(rect.Height);
int w = Next(m / 50);
int h = Next(m / 50);
g.FillEllipse(hatchBrush, x, y, w, h);
}
// Clean up.
font.Dispose();
hatchBrush.Dispose();
g.Dispose();
// Set the image.
this.image = bitmap;
}
/// <summary>
/// 获取一个随机数
/// </summary>
/// <returns>int</returns>
private int Next()
{
rand = new Random(unchecked((int)DateTime.Now.Ticks) * randseed++);
return rand.Next();
}
/// <summary>
/// 获取一个随机数
/// </summary>
/// <param name="maxValue">随机数的上界</param>
/// <returns>int</returns>
private int Next(int maxValue)
{
rand = new Random(unchecked((int)DateTime.Now.Ticks) * Next());
return rand.Next(maxValue);
}
/// <summary>
/// 获取一个随机数
/// </summary>
/// <param name="minValue">随机数的下界</param>
/// <param name="maxValue">随机数的上界</param>
/// <returns>int</returns>
private int Next(int minValue, int maxValue)
{
rand = new Random(unchecked((int)DateTime.Now.Ticks) * Next());
return rand.Next(minValue, maxValue);
}
}
}