随机验证码

<img id="img1" width="100" height="20" style="cursor: pointer" src="RandomCode.aspx" alt="看不清？点击更换" onclick="this.src=this.src+'?'" />

新建RandomCode.aspx

RandomCode.aspx.cs



using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;
using System.IO;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;

namespace WebApplication10
{
    public partial class RandomCode : System.Web.UI.Page
    {
        protected void Page_Load(object sender, System.EventArgs e)
        {
            // 在此处放置用户代码以初始化页面
            //RndNum是一个自定义函数
            string VNum = RndNum(4); //这里的数字8代表显示的是8位的验证字符串！
            Session["RandomCode"] = VNum;
            //ValidateCode(VNum);
            CreateValidateGraphic(VNum);
        }

        //生成图像函数
        private void ValidateCode(string VNum)
        {
            int Gheight = (int)(VNum.Length * 7);
            //gheight为图片宽度,根据字符长度自动更改图片宽度
            System.Drawing.Bitmap Img = new System.Drawing.Bitmap(Gheight, 12);
            Graphics g = Graphics.FromImage(Img);
            g.DrawString(VNum, new System.Drawing.Font("宋体", 9), new System.Drawing.SolidBrush(Color.Red), 0, 0);
            //在矩形内绘制字串（字串，字体，画笔颜色，左上x.左上y） 
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            Img.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
            Response.ClearContent(); //需要输出图象信息 要修改HTTP头 
            Response.ContentType = "image/Png";
            Response.BinaryWrite(ms.ToArray());
            g.Dispose();
            Img.Dispose();
            Response.End();
        }

        //生成随机数函数中从Vchar数组中随机抽取
        //字母区分大小写
        public string RndNum(int VcodeNum)
        {
            string Vchar = "A,B,C,D,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,U,W,X,Y,Z,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,U,W,X,Y,Z";
            //string Vchar = "零,壹,贰,叁,肆,伍,陆,柒,捌,玖,拾,湖,南,强,智,科,技,有,限,公,司,陈,伟,航,一,二,三,四,五,六,七,八,九,十,正" ;

            string[] VcArray = Vchar.Split(',');
            string VNum = "";//由于字符串很短，就不用StringBuilder了
            int temp = -1;//记录上次随机数值，尽量避免生产几个一样的随机数

            //采用一个简单的算法以保证生成随机数的不同
            Random rand = new Random();
            for (int i = 1; i < VcodeNum + 1; i++)
            {
                if (temp != -1)
                {
                    rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));
                }
                //int t =  rand.Next(35) ;
                int t = rand.Next(54);
                if (temp != -1 && temp == t)
                {
                    return RndNum(VcodeNum);
                }
                temp = t;
                VNum += VcArray[t];

            }
            return VNum;
        }

        public void CreateValidateGraphic(string validateNum)
        {
            //Bitmap image=new Bitmap((int)Math.Ceiling(validateNum.Length*12.5),22);
            Bitmap image = new Bitmap(70, 22);
            Graphics g = Graphics.FromImage(image);
            try
            {
                //生成随机生成器
                Random random = new Random();
                //清空图片背景色
                g.Clear(Color.White);
                //画图片的干扰线
                for (int i = 0; i < 25; i++)
                {
                    int x1 = random.Next(image.Width);
                    int x2 = random.Next(image.Width);
                    int y1 = random.Next(image.Height);
                    int y2 = random.Next(image.Height);
                    g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
                }
                Font font = new Font("Arial", 14, (FontStyle.Bold | FontStyle.Italic));
                LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
                g.DrawString(validateNum, font, brush, 3, 2);
                //画图片的前景干扰点
                for (int i = 0; i < 100; i++)
                {
                    int x = random.Next(image.Width);
                    int y = random.Next(image.Height);
                    image.SetPixel(x, y, Color.FromArgb(random.Next()));
                }
                //画图片的边框线
                g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
                //保存图片数据
                MemoryStream stream = new MemoryStream();
                image.Save(stream, ImageFormat.Jpeg);
                //输出图片
                Response.Clear();
                Response.ContentType = "image/jpeg";
                Response.BinaryWrite(stream.ToArray());
            }
            finally
            {
                g.Dispose();
                image.Dispose();
            }
        }
    }
}