C#.NET 验证码

 

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

namespace Pub.Class
{
    /// <summary>
    /// 验证码
    /// </summary>
    public class Identify
    {
        #region DrawIdentifyCode
        /// <summary>
        /// 验证码绘图
        /// </summary>
        /// <example>
        /// <code>
        ///     string strIdentifyCode = Pub.Class.Identify.IdentifyCode(4);
        ///     Pub.Class.Identify.DrawIdentifyCode(strIdentifyCode, 50, 100);
        ///     Response.End();
        ///     在登录页面引用此文件:&lt;img src="Identify.aspx" border="0" style="cursor: pointer;cursor:hand;" onclick="javascript:this.src='Identify.aspx?iTime=' + Math.random();" title="单击可更换新的验证码" />
        ///     Session["IdentifyCode"]
        /// </code>
        /// </example>
        /// <param name="strIdentifyCode">验证码</param>
        /// <param name="intFgNoise">文字噪音程度</param>
        /// <param name="intBgNoise">背景噪音程度</param>
        public static void DrawIdentifyCode(string strIdentifyCode, int intFgNoise, int intBgNoise)
        {
            if (strIdentifyCode == null || strIdentifyCode.Trim() == String.Empty) { return; }
            else {
                Bitmap bmpImage = new Bitmap((int)Math.Ceiling((strIdentifyCode.Length * 12.5)), 22);//建立一个位图文件 确立长宽
                Graphics grpGraphics = Graphics.FromImage(bmpImage);

                try {
                    Random rndRandom = new Random();//生成随机生成器
                    grpGraphics.Clear(Color.White);//清空图片背景色

                    for (int i = 0; i < intBgNoise; i++){//画图片的背景噪音线
                        int int_x1 = rndRandom.Next(bmpImage.Width);
                        int int_x2 = rndRandom.Next(bmpImage.Width);
                        int int_y1 = rndRandom.Next(bmpImage.Height);
                        int int_y2 = rndRandom.Next(bmpImage.Height);

                        grpGraphics.DrawLine(new Pen(Color.Silver), int_x1, int_y1, int_x2, int_y2);
                    }
                    Font font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));//把产生的随机数以字体的形式写入画面
                    LinearGradientBrush brhBrush = new LinearGradientBrush(new Rectangle(0, 0, bmpImage.Width, bmpImage.Height), Color.Blue, Color.DarkRed, 1.2f, true);
                    grpGraphics.DrawString(strIdentifyCode, font, brhBrush, 2, 2);
                    
                    for (int i = 0; i < intFgNoise; i++){//画图片的前景噪音点
                        int int_x = rndRandom.Next(bmpImage.Width);
                        int int_y = rndRandom.Next(bmpImage.Height);

                        bmpImage.SetPixel(int_x, int_y, Color.FromArgb(rndRandom.Next()));
                    }

                    grpGraphics.DrawRectangle(new Pen(Color.Silver), 0, 0, bmpImage.Width - 1, bmpImage.Height - 1);//画图片的边框线
                    MemoryStream memsMemoryStream = new MemoryStream();
                    bmpImage.Save(memsMemoryStream, ImageFormat.Gif);
                    System.Web.HttpContext.Current.Response.ClearContent();
                    System.Web.HttpContext.Current.Response.ContentType = "image/Gif";
                    System.Web.HttpContext.Current.Response.BinaryWrite(memsMemoryStream.ToArray());
                } finally {
                    grpGraphics.Dispose();
                    bmpImage.Dispose();
                }
            }
        }
        #endregion

        #region IdentifyCode
        /// <summary>
        /// 取得随机字符串，并设置Session值
        /// </summary>
        /// <example>
        /// <code>
        ///     string strIdentifyCode = Pub.Class.Identify.IdentifyCode(4);
        ///     Pub.Class.Identify.DrawIdentifyCode(strIdentifyCode, 50, 100);
        ///     Response.End();
        ///     在登录页面引用此文件:&lt;img src="Valid.aspx"  border="0" />
        ///     Session["IdentifyCode"]
        /// </code>
        /// </example>
        /// <param name="intLength"></param>
        /// <returns></returns>
        public static string IdentifyCode(int intLength)
        {
            int intNumber;
            char chrCode;
            string strIdentifyCode = String.Empty;
            Random rndRandom = new Random();
            for(int i=0;i<intLength;i++) {
                intNumber = rndRandom.Next();
                if(intNumber % 2 == 0) {
                    chrCode = (char)('0' + (char)(intNumber % 10));//如果随机数是偶数 取余
                } else {
                    chrCode = (char)('A' + (char)(intNumber % 26));//如果随机数是奇数 选择从[A-Z]
                }
                strIdentifyCode += chrCode.ToString(); 
            }
            Session2.Set("IdentifyCode", strIdentifyCode);
            return strIdentifyCode;
        }
        #endregion
    }
}