C#验证码，彩色背景的啊。_c# 验证码彩色-优快云博客

本文链接：https://blog.youkuaiyun.com/lxl743p/article/details/2493391

本文介绍了一个使用C#生成验证码图片的方法，包括随机数生成、图像绘制及噪点添加等步骤，适用于网站登录验证等功能。

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using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Drawing;
using System.Drawing.Imaging;

public partial class admin_Inc_checkcode : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        //RndNum是一个自定义函数
        string VNum = RndNum(4); //这里的数字4代表显示的是4位的验证字符串！
        Session["VNum"] = VNum;
        CreateImage(VNum);
    }
    //生成图像函数
    public void CreateImage(string VNum)
    {

        Bitmap image = new Bitmap(45, 15);
        Graphics g = Graphics.FromImage(image);
        WebColorConverter ww = new WebColorConverter();
        g.Clear((Color)ww.ConvertFromString("#FAE264"));

        Random random = new Random();
        //画图片的背景噪音线
        for (int i = 0; i < 12; 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.LightGray), x1, y1, x2, y2);
        }
        Font font = new Font("Arial", 11, FontStyle.Bold | FontStyle.Italic);
        System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(
            new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.Gray, 1.2f, true);
        g.DrawString(VNum, font, brush, 0, 0);

        //画图片的前景噪音点
        //for (int i = 0; i < 10; i++)
        //{
        //    int x = random.Next(image.Width);
        //    int y = random.Next(image.Height);
        //    image.SetPixel(x, y, Color.White);
        //}

        //画图片的边框线
        // g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

        System.IO.MemoryStream ms = new System.IO.MemoryStream();
        image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
        Response.ClearContent();
        Response.ContentType = "image/Gif";
        Response.BinaryWrite(ms.ToArray());
        g.Dispose();
        image.Dispose();
    }



    //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 = "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[] 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(35);
            if (temp != -1 && temp == t)
            {
                return RndNum(VcodeNum);
            }
            temp = t;
            VNum += VcArray[t];

        }
        return VNum;
    }
}