asp.net 生成验证码

Random ran = new Random();

protected void Page_Load(object sender, EventArgs e)

{

string str = getRandomValidate(4);

//这一步是为了将验证码写入Session，进行验证，不能缺省，也可一使用cookie

Session["check"] = str;

getImageValidate(str);

}

//得到随机字符串

private string getRandomValidate(int len)

{

int num;

int tem;

string rtuStr = "";

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

{

num = ran.Next();

/*

* 这里可以选择生成字符和数字组合的验证码

*/

tem = num % 10 + '0';//生成数字

//tem = num % 26 + 'A';//生成字符

rtuStr += Convert.ToChar(tem).ToString();

}

return rtuStr;

}

//将生成的随机数字转化成图像

private void getImageValidate(string strValue)

{

//string str = "OO00"; //前两个为字母O，后两个为数字0

int width = Convert.ToInt32(strValue.Length * 12); //计算图像宽度

Bitmap img = new Bitmap(width, 23);

Graphics gfc = Graphics.FromImage(img); //产生Graphics对象，进行画图

gfc.Clear(Color.White);

drawLine(gfc, img);

//写验证码，需要定义Font

Font font = new Font("arial", 12, FontStyle.Bold);

System.Drawing.Drawing2D.LinearGradientBrush brush =

new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, img.Width, img.Height), Color.DarkOrchid, Color.Blue, 1.5f, true);

gfc.DrawString(strValue, font, brush, 3, 2);

drawPoint(img);

gfc.DrawRectangle(new Pen(Color.DarkBlue), 0, 0, img.Width - 1, img.Height - 1);

//将图像添加到页面

MemoryStream ms = new MemoryStream();

img.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);

//更改Http头

Response.ClearContent();

Response.ContentType = "image/gif";

Response.BinaryWrite(ms.ToArray());

//Dispose

gfc.Dispose();

img.Dispose();

Response.End();

}

//画背景线

private void drawLine(Graphics gfc, Bitmap img)

{

//选择画10条线,也可以增加，也可以不要线，只要随机杂点即可

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

{

int x1 = ran.Next(img.Width);

int y1 = ran.Next(img.Height);

int x2 = ran.Next(img.Width);

int y2 = ran.Next(img.Height);

gfc.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2); //注意画笔一定要浅颜色，否则验证码看不清楚

}

}

//画背景点

private void drawPoint(Bitmap img)

{

/*

//选择画100个点,可以根据实际情况改变

for (int i = 0; i < 100; i++)

{

int x = ran.Next(img.Width);

int y = ran.Next(img.Height);

img.SetPixel(x,y,Color.FromArgb(ran.Next()));//杂点颜色随机

}

*/

int col = ran.Next();//在一次的图片中杂店颜色相同

for (int i = 0; i < 100; i++)

{

int x = ran.Next(img.Width);

int y = ran.Next(img.Height);

img.SetPixel(x, y, Color.FromArgb(col));

}

}

前台image控件：

<asp:Image ID="Image1" runat="server" ImageUrl="CreateImg.aspx" />

学习：

http://hi.baidu.com/rayshow/item/b778f522677f48cba4275a75