ASP.NET实现验证码图片

新建一个checkcode.aspx文件，页面中不用写任何东西asp验证码，在代码中，Page_Load中写入如下代码：

string chkCode = string.Empty;

int ix, iy;

ix = 80;

iy = 24;

//颜色列表，用于验证码、噪线、噪点

Color[] color ={ Color.Black, Color.Red, Color.Blue, Color.Green, Color.Orange, Color.Brown, Color.Brown, Color.DarkBlue };

//字体列表，用于验证码

string[] font ={ "Times New Roman", "MS Mincho", "Book Antiqua", "Gungsuh", "MingLiU", "Arial" };

//验证码的字符集，去掉了一些容易混淆的字符

char[] character ={ '2', '3', '4', '5', '6', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'R', 'S', 'T', 'W', 'X', 'Y' };

Random rnd = new Random();

//生成验证码字符串

for (int i = 0; i < 4; i++)

{

chkCode += character[rnd.Next(character.Length)];

}

Bitmap bmp = new Bitmap(ix, iy);

Graphics g = Graphics.FromImage(bmp);

g.Clear(Color.White);

//画噪线

for (int i = 0; i < 10; i++)

{

int x1 = rnd.Next(ix);

int y1 = rnd.Next(iy);

int x2 = rnd.Next(ix);

int y2 = rnd.Next(iy);

Color clr = color[rnd.Next(color.Length)];

g.DrawLine(new Pen(clr), x1, y1, x2, y2);

}

//画验证码字符串

for (int i = 0; i < chkCode.Length; i++)

{

string fnt = font[rnd.Next(font.Length)];

Font ft = new Font(fnt, 14, FontStyle.Bold);

Color clr = color[rnd.Next(color.Length)];

g.DrawString(chkCode[i].ToString(), ft, new SolidBrush(clr), (float)i * 16 + 2, (float)2);

}

//画噪点

for (int i = 0; i < 50; i++)

{

int x = rnd.Next(bmp.Width);

int y = rnd.Next(bmp.Height);

Color clr = color[rnd.Next(color.Length)];

bmp.SetPixel(x, y, clr);

}

//将验证码写入SESSION

Session["checkcode"] = chkCode.ToLower();

//清除该页输出缓存，设置该页无缓存

Response.Buffer = true;

Response.ExpiresAbsolute = System.DateTime.Now.AddMilliseconds(0);

Response.Expires = 0;

Response.CacheControl = "no-cache";

Response.AppendHeader("Pragma", "No-Cache");

//将验证码图片写入内存流，并将其以 "image/Png" 格式输出

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