asp.net登录验证码

2019独角兽企业重金招聘Python工程师标准>>>

前台代码

<form method="POST" action="CheckUser.aspx" id="fromLogin">            
            <table>
                <tr>
                    <td><img src="ValidCode.aspx" alt='看不清楚，双击图片换一张。'ondblclick=" this.src = 'ValidCode.aspx?flag=' + Math.random() " border="1" height="44" width="126"/></td>
                </tr>                
            </table>
        </form>

验证码生成页：ValidCode.aspx

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;
using System.Web.UI;

namespace CST.WebApp
{
    public partial class ValidCode : Page
    {
        private readonly Random ran = new Random();

        protected void Page_Load(object sender, EventArgs e)
        {
            string str = getRandomValidate(5);
            Session["check"] = str;
            //这一步是为了将验证码写入Session，进行验证，不能缺省，也可一使用cookie
            getImageValidate(str);
        }

        //得到随机字符串,长度自己定义
        private string getRandomValidate(int len)
        {
            int num;
            int tem;
            string rtuStr = "";
            for (int i = 0; i < len; i++)
            {
                num = ran.Next();
                if (i%2 == 0)
                {
                    tem = num%10 + '0'; //生成数字 
                }
                else
                {
                    tem = num%26 + 'A'; //生成字符
                }
                rtuStr += Convert.ToChar(tem).ToString() + " ";
            }
            return rtuStr;
        }

        //生成图像
        private void getImageValidate(string strValue)
        {
            //string str = "OO00"; //前两个为字母O，后两个为数字0
            //int width = Convert.ToInt32(strValue.Length*12); //计算图像宽度
            // var img = new Bitmap(width, 141);
            var img = new Bitmap(150, 42);
            Graphics gfc = Graphics.FromImage(img); //产生Graphics对象，进行画图
            gfc.Clear(Color.White);
            drawLine(gfc, img);
            //写验证码，需要定义Font
            var font = new Font("Brush Script Std", 16);
            var brush =
                new LinearGradientBrush(new Rectangle(0, 0, img.Width, img.Height), Color.DarkOrchid, Color.Blue, 1.5f,
                                        true);
            gfc.DrawString(strValue, font, brush, 20, 9);
            drawPoint(img);
            gfc.DrawRectangle(new Pen(Color.DarkGray), 0, 0, img.Width - 1, img.Height - 1);
            //将图像添加到页面
            var ms = new MemoryStream();
            img.Save(ms, ImageFormat.Gif);
            //更改Http头
            Response.ClearContent();
            Response.ContentType = "image/gif";
            Response.BinaryWrite(ms.ToArray());
            //Dispose
            gfc.Dispose();
            img.Dispose();
            Response.End();
        }

        private void drawLine(Graphics gfc, Bitmap img)
        {
            //选择画10条线,也可以增加，也可以不要线，只要随机杂点即可
            for (int i = 0; i < 10; i++)
            {
                int x1 = ran.Next(img.Width);
                int y1 = ran.Next(img.Height);
                int x2 = ran.Next(img.Width);
                int y2 = ran.Next(img.Height);
                gfc.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2); //注意画笔一定要浅颜色，否则验证码看不清楚
            }
        }

        private void drawPoint(Bitmap img)
        {
            int col = ran.Next(); //在一次的图片中杂店颜色相同
            for (int i = 0; i < 100; i++)
            {
                int x = ran.Next(img.Width);
                int y = ran.Next(img.Height);
                img.SetPixel(x, y, Color.FromArgb(col));
            }
        }
    }
}

转载于:https://my.oschina.net/mandy4107/blog/480785