C#一款比较美观的验证码

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;
using System.IO;
using System.Drawing.Imaging;

public partial class ValidateCode : System.Web.UI.Page
{
private int letterWidth = 16;//单个字体的宽度范围
private int letterHeight = 22;//单个字体的高度范围
private int letterCount = 4;//验证码位数
private char[] chars = "0123456789".ToCharArray();
private string[] fonts = { "Arial", "Georgia" };
/// <summary>
/// 产生波形滤镜效果
/// </summary>
private const double PI = 3.1415926535897932384626433832795;
private const double PI2 = 6.283185307179586476925286766559;
protected void Page_Load(object sender, EventArgs e)
{
//防止网页后退--禁止缓存
Response.Expires = 0;
Response.Buffer = true;
Response.ExpiresAbsolute = DateTime.Now.AddSeconds(-1);
Response.AddHeader("pragma", "no-cache");
Response.CacheControl = "no-cache";
string str_ValidateCode = GetRandomNumberString(letterCount);
HttpCookie objCookie = new HttpCookie("ValidateCode");
objCookie.Value = str_ValidateCode;
objCookie.Path = "/";
objCookie.Expires = DateTime.Now.AddSeconds(1200);
Response.Cookies.Add(objCookie);
CreateImage(str_ValidateCode);

}
public void CreateImage(string checkCode)
{
int int_ImageWidth = checkCode.Length * letterWidth;
Random newRandom = new Random();
Bitmap image = new Bitmap(int_ImageWidth, letterHeight);
Graphics g = Graphics.FromImage(image);
//生成随机生成器
Random random = new Random();
//白色背景
g.Clear(Color.White);
//画图片的背景噪音线
for (int i = 0; i < 10; i++)
{
int x1 = random.Next(image.Width);
int x2 = random.Next(image.Width);
int y1 = random.Next(image.Height);
int y2 = random.Next(image.Height);

g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
}

//画图片的前景噪音点
for (int i = 0; i < 10; i++)
{
int x = random.Next(image.Width);
int y = random.Next(image.Height);

image.SetPixel(x, y, Color.FromArgb(random.Next()));
}
//随机字体和颜色的验证码字符

int findex;
for (int int_index = 0; int_index < checkCode.Length; int_index++)
{
findex = newRandom.Next(fonts.Length - 1);
string str_char = checkCode.Substring(int_index, 1);
Brush newBrush = new SolidBrush(GetRandomColor());
Point thePos = new Point(int_index * letterWidth + 1 + newRandom.Next(3), 1 + newRandom.Next(3));//5+1+a+s+p+x
g.DrawString(str_char, new Font(fonts[findex], 12, FontStyle.Bold), newBrush, thePos);
}
//灰色边框
g.DrawRectangle(new Pen(Color.LightGray, 1), 0, 0, int_ImageWidth - 1, (letterHeight - 1));
//图片扭曲
//image = TwistImage(image, true, 3, 4);
//将生成的图片发回客户端
MemoryStream ms = new MemoryStream();
image.Save(ms, ImageFormat.Png);
Response.ClearContent(); //需要输出图象信息 要修改HTTP头
Response.ContentType = "image/Png";
Response.BinaryWrite(ms.ToArray());
g.Dispose();
image.Dispose();
}
/// <summary>
/// 正弦曲线Wave扭曲图片
/// </summary>
/// <param name="srcBmp">图片路径</param>
/// <param name="bXDir">如果扭曲则选择为True</param>
/// <param name="nMultValue">波形的幅度倍数，越大扭曲的程度越高，一般为3</param>
/// <param name="dPhase">波形的起始相位，取值区间[0-2*PI)</param>
/// <returns></returns>
public System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)
{
System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);
// 将位图背景填充为白色
System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp);
graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);
graph.Dispose();
double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;

for (int i = 0; i < destBmp.Width; i++)
{
for (int j = 0; j < destBmp.Height; j++)
{
double dx = 0;
dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen;
dx += dPhase;
double dy = Math.Sin(dx);
// 取得当前点的颜色
int nOldX = 0, nOldY = 0;
nOldX = bXDir ? i + (int)(dy * dMultValue) : i;
nOldY = bXDir ? j : j + (int)(dy * dMultValue);
System.Drawing.Color color = srcBmp.GetPixel(i, j);
if (nOldX >= 0 && nOldX < destBmp.Width && nOldY >= 0 && nOldY < destBmp.Height)
{
destBmp.SetPixel(nOldX, nOldY, color);
}
}
}
return destBmp;
}

public Color GetRandomColor()
{
Random RandomNum_First = new Random((int)DateTime.Now.Ticks);
System.Threading.Thread.Sleep(RandomNum_First.Next(50));
Random RandomNum_Sencond = new Random((int)DateTime.Now.Ticks);
int int_Red = RandomNum_First.Next(210);
int int_Green = RandomNum_Sencond.Next(180);
int int_Blue = (int_Red + int_Green > 300) ? 0 : 400 - int_Red - int_Green;
int_Blue = (int_Blue > 255) ? 255 : int_Blue;
return Color.FromArgb(int_Red, int_Green, int_Blue);// 5+1+a+s+p+x
}

//  生成随机数字字符串
public string GetRandomNumberString(int int_NumberLength)
{
Random random = new Random();
string validateCode = string.Empty;
for (int i = 0; i < int_NumberLength; i++)
validateCode += chars[random.Next(0, chars.Length)].ToString();
return validateCode;
}
}

<img alt="看不清，换一张" title="看不清，换一张" src="ValidateCode.aspx" style="cursor:pointer" onclick="this.src=this.src+'?r='+Math.random()" />