asp 验证码 实现

VCode.cs​

protected void Page_Load(object sender, EventArgs e)

{

//调用方法，生成验证码

string code = getNum(5);

Session[EnumConst.VCODE_SESSION] = code;//将验证码保存在Session内置对象中

StringBuilder str = new StringBuilder();

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

{

str.Append(code.Substring(i, 1) + " ");

}

createImage(str.ToString());

}

 

//生成随机数

private string getNum(int stringLength)

{

StringBuilder str = new StringBuilder();

Random ran = new Random();

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

{

str.Append(ran.Next(10)); //生成0-9的数字

}

return str.ToString(); //返回字符

}

//获得验证图片

private void createImage(string stringCode)

{

Bitmap image = new Bitmap(stringCode.Length * 12, 30); //设置图片大小

Graphics g = Graphics.FromImage(image); //定义画笔

g.Clear(Color.White); //背景颜色

string[] fonts = { "FZSTK", "VINERITC", "STCAIYUN", "HARNGTON" };

Color[] colors = { Color.Red, Color.Green, Color.Blue};

Random random = new Random();

int x = 10;

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

{

string strCode = stringCode.Substring(i, 1);

Font font = new System.Drawing.Font(fonts[random.Next(0, 4)], 16, (System.Drawing.FontStyle.Bold));

g.DrawString(strCode, font, new SolidBrush(colors[random.Next(0, 3)]), x, 5);

x = x + 10;

}

// 画图片的边框线

g.DrawRectangle(new Pen(Color.Blue), 0, 0, image.Width - 1, image.Height - 1);

image.Save(Response.OutputStream, ImageFormat.Gif);//显示到页面

g.Dispose();

image.Dispose();

}​

前台​

<img id="img_captcha" onclick="changeCaptcha()" title="点击更换验证码" /><span id="sMsg" runat="server" style="color: red; max-width: 100px;"></span>

 

//更换验证码

function changeCaptcha() {

document.getElementByIdx_x_x("img_captcha").src = 'Resources/VCode.aspx?_r=' + Math.random();

}