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.Drawing2D;using System.Drawing.Imaging;public partial class user_Default : System.Web.UI.Page{    protected void Page_Load(object sender, EventArgs e)    {        string checkCode = CreateRandomCode(4);        GetImgWithValidateCode(checkCode, 132, 35,20);    }    ///
    /// 生成随机字符串    ///
    ///字符数量    ///
     
      随机字符串
         private string CreateRandomCode(int codeCount)    {        string allChar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z";        string[] allCharArray = allChar.Split(',');        string randomCode = "";        int temp = -1;        Random rand = new Random();        for (int i = 0; i < codeCount; i++)        {            if (temp != -1)            {                rand = new Random(i * temp * ((int)DateTime.Now.Ticks));            }            int t = rand.Next(35);            if (temp == t)            {                return CreateRandomCode(codeCount);            }            temp = t;            randomCode += allCharArray[t];        }        return randomCode;    }    ///
    /// 创建验证码图片    ///
    ///字符串    ///宽    ///高    ///字号    public void GetImgWithValidateCode(string code, int width, int height, int fontSize)    {        Color bgcolor = GetControllableColor(150);        Color color = GetControllableColor(100);        int charNum = code.Length;        Bitmap bitMap = null;        Graphics gph = null;        //创建内存流         MemoryStream memStream = new MemoryStream();        Random random = new Random();        //创建位图对象        bitMap = new Bitmap(width, height);        //根据上面创建的位图对象创建绘图图面        gph = Graphics.FromImage(bitMap);        //设定验证码图片背景色        gph.Clear(bgcolor);        //产生随机干扰线条         for (int i = 0; i < 1; i++)        {            Pen backPen = new Pen(color, 2);            int x = 0;            int y = height / 2;            int x2 = width;            int y2 = random.Next(height);            gph.DrawLine(backPen, x, y, x2, y2);        }        SolidBrush sb = new SolidBrush(color);        PointF Cpoint1 = new PointF(5, 5);        Random rnd1 = new Random();        int x1 = 0, y1 = 0;        //通过循环,绘制每个字符,        for (int i = 0; i < code.Length; i++)        {            x1 = rnd1.Next(2) + ((width - 10) / code.Length) * i;            y1 = rnd1.Next(bitMap.Height / 4);            Cpoint1 = new PointF(x1, y1);            Font textFont = new Font("Arial", fontSize, FontStyle.Bold);//字体随机,字号大小30,加粗            //随机倾斜字符            Matrix transform = gph.Transform;            transform.Shear(Convert.ToSingle(rnd1.NextDouble() - 0.5), 0.001f);            gph.Transform = transform;            gph.DrawString(code.Substring(i, 1), textFont, sb, Cpoint1);            gph.ResetTransform();        }        //画图片的前景噪音点        for (int i = 0; i < 10; i++)        {            int x = random.Next(bitMap.Width);            int y = random.Next(bitMap.Height);            bitMap.SetPixel(x, y, Color.White);        }        //画图片的边框线        gph.DrawRectangle(new Pen(Color.Black, 2), 0, 0, bitMap.Width - 1, bitMap.Height - 1);        try        {            bitMap.Save(memStream, ImageFormat.Gif);        }        catch (Exception ex)        {            Console.WriteLine(ex.Message);        }        bitMap.Dispose();        System.Drawing.Image img = System.Drawing.Image.FromStream(memStream);        gph.DrawImage(img, 50, 20, width, height);        //img.Save(@"D:\test.jpg", ImageFormat.Jpeg);        //如果是asp.net 用下面的输出图片        System.IO.MemoryStream ms = new System.IO.MemoryStream();        img.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);        Response.ClearContent();        Response.ContentType = "image/Jpeg";        Response.BinaryWrite(ms.ToArray());        gph.Dispose();        img.Dispose();    }    ///
     /// 产生一种 R,G,B 均大于 colorBase 随机颜色，以确保颜色不会过深     ///
     ///The color base.     ///
     
      Color
         public Color GetControllableColor(int colorBase)    {        Color color = Color.Black;        if (colorBase > 200)        {            return color;        }        Random random = new Random();        color = Color.FromArgb(random.Next(56) + colorBase, random.Next(56) + colorBase, random.Next(56) + colorBase);        return color;    }}

验证码效果：

还有2种验证码请看我博客

http://www.cnblogs.com/webapi/p/5725576.html

http://www.cnblogs.com/webapi/p/5726498.html