Ajax校验验证码(可以设置为数字、字母、中文汉字等,背景图有干扰线)

一般处理程序,获得验证码

    /// <summary>
    /// VCode 的摘要说明
    /// </summary>
    public class VCode : IHttpHandler,System.Web.SessionState.IRequiresSessionState
    {
        public void ProcessRequest(HttpContext context)
        {
            //System.Threading.Thread.Sleep(5000);
            context.Response.ContentType = "image/jpeg";
            string code = GetRndNumStr();
            //string code = GetRndNum();
            //string code = GetRndStr();
            //string code = GetRndCh();
            context.Session["VCode"] = code;
            using (Bitmap img = CreateImages(code, "ch"))
            {
                img.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
        }
        // 数字+字母随机
        private string GetRndNumStr()
        {
            string Vchar = "A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z,0,1,2,3,4,5,6,7,8,9";
            string[] VcArray = Vchar.Split(',');
            string checkCode = string.Empty;
            Random rand = new Random();
            for (int i = 0; i < 4; i++)
            {
                int t = rand.Next(VcArray.Length);
                checkCode += VcArray[t];
            }
            return checkCode;
        }
        // 数字随机数
        private string GetRndNum()
        {
            string code = string.Empty;
            Random random = new Random();
            for (int i = 0; i < 4; i++)
            {
                code += random.Next(9);
            }
            return code;
        }
        // 英文随机
        private string GetRndStr()
        {
            string Vchar = "A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z";
            string[] VcArray = Vchar.Split(',');
            string checkCode = string.Empty;
            Random rand = new Random();
            for (int i = 0; i < 4; i++)
            {
                int t = rand.Next(VcArray.Length);
                checkCode += VcArray[t];
            }
            return checkCode;
        }
        // 中文随机
        private string GetRndCh()
        {
            System.Text.Encoding gb = System.Text.Encoding.Default;//获取GB2312编码页(表)
            object[] bytes = CreateRegionCode(4);//生4个随机中文汉字编码
            string[] str = new string[4];
            System.Text.StringBuilder sb = new System.Text.StringBuilder();
            for (int i = 0; i < 4; i++)
            {
                //根据汉字编码的字节数组解码出中文汉字
                str[i] = gb.GetString((byte[])Convert.ChangeType(bytes[i], typeof(byte[])));
                sb.Append(str[i].ToString());
            }
            return sb.ToString();
        }
        // 产生随机中文字符
        private static object[] CreateRegionCode(int strlength)
        {
            //定义一个字符串数组储存汉字编码的组成元素
            string[] rBase = new String[16] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };
            Random rnd = new Random();
            object[] bytes = new object[strlength];

            for (int i = 0; i < strlength; i++)
            {
                //区位码第1位
                int r1 = rnd.Next(11, 14);
                string str_r1 = rBase[r1].Trim();
                //区位码第2位
                rnd = new Random(r1 * unchecked((int)DateTime.Now.Ticks) + i);
                int r2;
                if (r1 == 13)
                {
                    r2 = rnd.Next(0, 7);
                }
                else
                {
                    r2 = rnd.Next(0, 16);
                }
                string str_r2 = rBase[r2].Trim();

                //区位码第3位
                rnd = new Random(r2 * unchecked((int)DateTime.Now.Ticks) + i);//更换随机种子
                int r3 = rnd.Next(10, 16);
                string str_r3 = rBase[r3].Trim();

                //区位码第4位
                rnd = new Random(r3 * unchecked((int)DateTime.Now.Ticks) + i);
                int r4;
                if (r3 == 10)
                {
                    r4 = rnd.Next(1, 16);
                }
                else if (r3 == 15)
                {
                    r4 = rnd.Next(0, 15);
                }
                else
                {
                    r4 = rnd.Next(0, 16);
                }
                string str_r4 = rBase[r4].Trim();
                //定义两个字节变量存储产生的随机汉字区位码
                byte byte1 = Convert.ToByte(str_r1 + str_r2, 16);
                byte byte2 = Convert.ToByte(str_r3 + str_r4, 16);

                //将两个字节变量存储在字节数组中
                byte[] str_r = new byte[] { byte1, byte2 };

                //将产生的一个汉字的字节数组放入object数组中
                bytes.SetValue(str_r, i);
            }
            return bytes;
        }
        // 画图片的背景图+干扰线 
        private Bitmap CreateImages(string checkCode, string type)
        {
            int step = 0;
            if (type == "ch")
            {
                step = 5;//中文字符,边界值做大
            }
            int iwidth = (int)(checkCode.Length * (13 + step));
            System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 22);
            Graphics g = Graphics.FromImage(image);
            g.Clear(Color.White);//清除背景色
            Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };//定义随机颜色
            string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };
            Random rand = new Random();

            for (int i = 0; i < 50; i++)
            {
                int x1 = rand.Next(image.Width);
                int x2 = rand.Next(image.Width);
                int y1 = rand.Next(image.Height);
                int y2 = rand.Next(image.Height);
                g.DrawLine(new Pen(Color.LightGray, 1), x1, y1, x2, y2);//根据坐标画线
            }

            for (int i = 0; i < checkCode.Length; i++)
            {
                int cindex = rand.Next(7);
                int findex = rand.Next(5);

                Font f = new System.Drawing.Font(font[findex], 10, System.Drawing.FontStyle.Bold);
                Brush b = new System.Drawing.SolidBrush(c[cindex]);
                int ii = 4;
                if ((i + 1) % 2 == 0)
                {
                    ii = 2;
                }
                g.DrawString(checkCode.Substring(i, 1), f, b, 3 + (i * (12 + step)), ii);

            }
            g.DrawRectangle(new Pen(Color.Black, 0), 0, 0, image.Width - 1, image.Height - 1);
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            return image;
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
HTML代码
    验证码:
    <input id="txtVcode" type="text" />
    <img alt="" id="imgCode" src="/js/vcode/VCode.ashx" />
    <a id="aCode" href="javascript:void(0)">看不清,换一张</a>
    <div id="txtVcodeTip"></div>
Javascript变换验证码代码
function getVCode() {
    $("#imgCode").attr("src", "/js/vcode/VCode.ashx?r=" + new Date());
}
$(function () {
    //验证码
    var imgCode = $("#imgCode");
    imgCode.attr("alt", "点击获取验证码");
    imgCode.attr("title", "点击更换验证码");
    imgCode.css("cursor", "pointer");
    imgCode.click(function () {//点击验证码本身切换验证码
        getVCode();
    });
    //点击文字超链接更换验证码
    var aCode = $("#aCode");
    aCode.click(function () {
        getVCode();
    });
    //验证码提示消息
    var vcodeMsg = $("#txtVcodeTip");
    vcodeMsg.css("color", "Red");
    var vcode = $("#txtVcode");
    vcode.blur(function () {
        if ($.trim(vcode.val()) == '') {
            vcodeMsg.text("验证码不能为空");
            return false;
        } else {
            $.post("/js/vcode/CheckVCode.ashx", { "vcode": $.trim(vcode.val()) }, function (data) {
                vcodeMsg.text(data);
            });
        }
    }).focus(function () {
        vcodeMsg.text("");
    });
});

CheckVCode.ashx代码

    public class CheckVCode : IHttpHandler, System.Web.SessionState.IRequiresSessionState
    {

        public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/plain";
            string vcode = context.Request["vcode"];
            context.Response.Write(CheckCode(vcode));
        }

        public static string CheckCode(string vcode)
        {
            if (HttpContext.Current.Session["VCode"] != null)
            {
                string sysCode = HttpContext.Current.Session["VCode"].ToString();
                //使用  Compare  方法,这个方法可以做大小写忽略的比较,并且不会创建新字符串
                if (String.Compare(vcode, sysCode, true) == 0)
                {
                    return "ok";
                }
                else
                {
                    return "验证码输入错误,重新输入";
                }
            }
            else
            {
                return "验证码过期,请更换验证码";
            }
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }


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原文地址:https://www.cnblogs.com/ful1021/p/4804477.html