验证码图片.cs

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;

public partial class UserControls_GetVerifyImage : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        string strKey = "";
        byte[] data = GenerateVerifyImage(5, ref strKey);
        Session["VerifyNumber"] = strKey;
        Response.OutputStream.Write(data, 0, data.Length);
    }

    private static byte[] GenerateVerifyImage(int nLen, ref string strKey)
    {
        int nBmpWidth = 13 * nLen + 5;
        int nBmpHeight = 25;
        System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(nBmpWidth, nBmpHeight);

        // 1. 生成随机背景颜色

        int nRed, nGreen, nBlue;　// 背景的三元色
        System.Random rd = new Random((int)System.DateTime.Now.Ticks);
        nRed = rd.Next(255) % 128 + 128;
        nGreen = rd.Next(255) % 128 + 128;
        nBlue = rd.Next(255) % 128 + 128;

        // 2. 填充位图背景

        System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(bmp);
        graph.FillRectangle(new SolidBrush(System.Drawing.Color.FromArgb(nRed, nGreen, nBlue))
        , 0
        , 0
        , nBmpWidth
        , nBmpHeight);

        // 3. 绘制干扰线条，采用比背景略深一些的颜色

        int nLines = 3;
        System.Drawing.Pen pen = new System.Drawing.Pen(System.Drawing.Color.FromArgb(nRed - 17, nGreen - 17, nBlue - 17), 2);
        for (int a = 0; a < nLines; a++)
        {
            int x1 = rd.Next() % nBmpWidth;
            int y1 = rd.Next() % nBmpHeight;
            int x2 = rd.Next() % nBmpWidth;
            int y2 = rd.Next() % nBmpHeight;
            graph.DrawLine(pen, x1, y1, x2, y2);
        }

        // 采用的字符集，可以随即拓展，并可以控制字符出现的几率
        // 这里剔除了一些容易混淆的字符
        string strCode = "2345678abcdefghijkmnprstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ";

        // 4. 循环取得字符，并绘制

        string strResult = "";
        for (int i = 0; i < nLen; i++)
        {
            int x = (i * 13 + rd.Next(3));
            int y = rd.Next(4) + 1;

            // 确定字体

            System.Drawing.Font font = new System.Drawing.Font("Courier New",
             12 + rd.Next() % 4,
             System.Drawing.FontStyle.Bold);
            char c = strCode[rd.Next(strCode.Length)];　// 随机获取字符
            strResult += c.ToString();

            // 绘制字符

            graph.DrawString(c.ToString(),
             font,
             new SolidBrush(System.Drawing.Color.FromArgb(nRed - 60 + y * 3, nGreen - 60 + y * 3, nBlue - 40 + y * 3)),
             x,
             y);
        }

        // 5. 输出字节流

        System.IO.MemoryStream bstream = new System.IO.MemoryStream();
        bmp.Save(bstream, System.Drawing.Imaging.ImageFormat.Jpeg);
        bmp.Dispose();
        graph.Dispose();

        strKey = strResult;
        byte[] byteReturn = bstream.ToArray();
        bstream.Close();

        return byteReturn;
    }
}