asp.net 验证码

专门处理图片的ashx文件:

<%@ WebHandler Language="C#" Class="VerificationHandler" %>

using System;
using System.Web;
using System.IO;

public class VerificationHandler : IHttpHandler, System.Web.SessionState.IRequiresSessionState
{
    public void ProcessRequest(HttpContext context)
    {
        AVerificationCode verificationCode = new VerificationCode();
        verificationCode.FontSize = 30;
        string code = verificationCode.CreateVerifyCode(4);
        System.Drawing.Bitmap bitImage = verificationCode.CreateImageCode(code);
        using (MemoryStream ms = new MemoryStream())
        {
            try
            {
                context.Session["checkcode"] = code;
                bitImage.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
                context.Response.Clear();
                context.Response.BinaryWrite(ms.GetBuffer());
                ms.Close();
                context.Response.End();
            }
            catch
            {
            }
            finally
            {
                bitImage.Dispose();
                ms.Dispose();
            }

        }
    }

    public bool IsReusable
    {
        get
        {
            return false;
        }
    }

}

AVerificationCode类文件(网上转的):

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Drawing;

/// <summary>
/// Summary description for VerificationCode
/// </summary>
public abstract class AVerificationCode
{
    #region common properies
    #region 验证码长度(默认6个验证码的长度)
    int length = 6;
    /// <summary>
    /// 验证码长度(默认6个验证码的长度)
    /// </summary>
    public int Length
    {
        get { return length; }
        set { length = value; }
    }
    #endregion

    #region 验证码字体大小(为了显示扭曲效果，默认40像素，可以自行修改)
    int fontSize = 40;
    /// <summary>
    /// 验证码字体大小(为了显示扭曲效果，默认40像素，可以自行修改)
    /// </summary>
    public int FontSize
    {
        get { return fontSize; }
        set { fontSize = value; }
    }
    #endregion

    #region 边框补(默认1像素)
    int padding = 2;
    /// <summary>
    /// 边框补(默认1像素)
    /// </summary>
    public int Padding
    {
        get { return padding; }
        set { padding = value; }
    }
    #endregion

    #region 是否输出燥点(默认输出)
    bool chaos = true;
    /// <summary>
    /// 是否输出燥点(默认输出)
    /// </summary>
    public bool Chaos
    {
        get { return chaos; }
        set { chaos = value; }
    }
    #endregion

    #region 输出燥点的颜色(默认灰色)
    Color chaosColor = Color.Green;
    /// <summary>
    /// 输出燥点的颜色(默认灰色)
    /// </summary>
    public Color ChaosColor
    {
        get { return chaosColor; }
        set { chaosColor = value; }
    }
    #endregion

    #region 自定义背景色(默认白色)
    Color backgroundColor = Color.White;
    /// <summary>
    /// 自定义背景色(默认白色)
    /// </summary>
    public Color BackgroundColor
    {
        get { return backgroundColor; }
        set { backgroundColor = value; }
    }
    #endregion

    #region 自定义随机颜色数组
    Color[] colors = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
    /// <summary>
    /// 自定义随机颜色数组
    /// </summary>
    public Color[] Colors
    {
        get { return colors; }
        set { colors = value; }
    }
    #endregion

    #region 自定义字体数组
    string[] fonts = { "Gungsuh", "Viner Hand ITC" };
    /// <summary>
    /// 自定义字体数组
    /// </summary>
    public string[] Fonts
    {
        get { return fonts; }
        set { fonts = value; }
    }
    #endregion

    #region 自定义随机码字符串序列(使用逗号分隔)
    string codeSerial = "2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,j,k,m,n,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,J,K,M,N,P,Q,R,S,T,U,V,W,X,Y,Z";
    /// <summary>
    /// 自定义随机码字符串序列(使用逗号分隔)
    /// </summary>
    public string CodeSerial
    {
        get { return codeSerial; }
        set { codeSerial = value; }
    }
    #endregion
    #endregion
    #region 产生波形滤镜效果

    private const double PI = 3.1415926535897932384626433832795;
    private const double PI2 = 6.283185307179586476925286766559;

    /// <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 virtual 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;
    }



    #endregion

    #region 生成校验码图片
    /// <summary>
    /// 生成校验码图片
    /// </summary>
    /// <param name="code"></param>
    /// <returns></returns>
    public virtual Bitmap CreateImageCode(string code)
    {
        int fSize = FontSize;
        int fWidth = fSize + Padding;

        int imageWidth = (int)(code.Length * fWidth) + 4 + Padding * 2;
        int imageHeight = fSize * 2 + Padding;

        System.Drawing.Bitmap image = new System.Drawing.Bitmap(imageWidth, imageHeight);

        Graphics g = Graphics.FromImage(image);
        try
        {
            g.Clear(BackgroundColor);

            Random rand = new Random();

            //给背景添加随机生成的燥点
            if (this.Chaos)
            {

                Pen pen = new Pen(ChaosColor, 0);
                int c = Length * 10;

                for (int i = 0; i < c; i++)
                {
                    int x = rand.Next(image.Width);
                    int y = rand.Next(image.Height);

                    g.DrawRectangle(pen, x, y, 1, 1);
                }
            }

            int left = 0, top = 0, top1 = 1, top2 = 1;

            int n1 = (imageHeight - FontSize - Padding * 2);
            int n2 = n1 / 4;
            top1 = n2;
            top2 = n2 * 2;

            Font f;
            Brush b;

            int cindex, findex;


            //随机字体和颜色的验证码字符
            for (int i = 0; i < code.Length; i++)
            {
                cindex = rand.Next(Colors.Length - 1);
                findex = rand.Next(Fonts.Length - 1);

                f = new System.Drawing.Font(Fonts[findex], fSize, System.Drawing.FontStyle.Bold);
                b = new System.Drawing.SolidBrush(Colors[cindex]);
                try
                {


                    if (i % 2 == 1)
                    {
                        top = top2;
                    }
                    else
                    {
                        top = top1;
                    }

                    left = i * fWidth;

                    g.DrawString(code.Substring(i, 1), f, b, left, top);
                }
                catch
                {
                }
                finally
                {
                    f.Dispose();
                    b.Dispose();
                }
            }

            //画一个边框 边框颜色为Color.Gainsboro
            g.DrawRectangle(new Pen(Color.Gainsboro, 0), 0, 0, image.Width - 1, image.Height - 1);
        }
        catch
        {

        }
        finally
        {
            g.Dispose();
        }
        //产生波形（Add By 51aspx.com）
        image = TwistImage(image, true, 10, 4);

        return image;
    }
    #endregion

    #region 将创建好的图片输出到页面
    /// <summary>
    /// 将创建好的图片输出到页面
    /// </summary>
    /// <param name="code"></param>
    /// <param name="context"></param>
    public virtual void CreateImageOnPage(string code, HttpContext context)
    {
        System.IO.MemoryStream ms = new System.IO.MemoryStream();
        Bitmap image = this.CreateImageCode(code);

        image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);

        context.Response.ClearContent();
        context.Response.ContentType = "image/Jpeg";
        context.Response.BinaryWrite(ms.GetBuffer());

        ms.Close();
        ms = null;
        image.Dispose();
        image = null;
    }
    #endregion

    #region 生成随机字符码
    /// <summary>
    /// 生成随机字符码
    /// </summary>
    /// <param name="codeLen"></param>
    /// <returns></returns>
    public virtual string CreateVerifyCode(int codeLen)
    {
        if (codeLen == 0)
        {
            codeLen = Length;
        }

        string[] arr = CodeSerial.Split(',');

        string code = "";

        int randValue = -1;

        Random rand = new Random(unchecked((int)DateTime.Now.Ticks));

        for (int i = 0; i < codeLen; i++)
        {
            randValue = rand.Next(0, arr.Length - 1);

            code += arr[randValue];
        }

        return code;
    }
    #endregion
}

VerificationCode类文件:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;


/// <summary>
/// Summary description for VerificationCode
/// </summary>
public class VerificationCode : AVerificationCode
{
    public VerificationCode()
    {
        //
        // TODO: Add constructor logic here
        //
    }
}

html使用:

<img alt="Click to update the verification code" height="40px" src="../VerificationHandler.ashx"
                        id="verificationCodeImage" onclick="this.src='../VerificationHandler.ashx?r='+Math.random()+'&t='+ new Date().getMilliseconds()" />(See
                    clearly? Please click the picture) <span style="color: Red; display: none;" id="errorSpan">
                        Verification Code fill in error</span>