C#验证码

using System;

using System.Drawing;

using System.Drawing.Drawing2D;

using System.Drawing.Imaging;

using System.IO;

using System.Text;

using System.Web;

namespace Demo

{

    /// <summary>

    /// Captcha

    /// </summary>

    public class Captcha

    {

        #region Private Field

        /// <summary>

        /// 随机种子

        /// </summary>

        private Random objRandom = new Random();

        #endregion

        #region Public Property

        #region 验证码长度

        /// <summary>

        /// 验证码长度

        /// </summary>

        private int length = 4;

        /// <summary>

        /// 验证码长度(默认为4)

        /// </summary>

        public int Length

        {

            get { return this.length; }

            set { this.length = value; }

        }

        #endregion

        #region 验证码字符串

        /// <summary>

        /// 验证码字符串

        /// </summary>

        private string verifyCodeText = null;

        /// <summary>

        /// 验证码字符串

        /// </summary>

        public string VerifyCodeText

        {

            get { return this.verifyCodeText; }

            set { this.verifyCodeText = value; }

        }

        #endregion

        #region 是否加入小写字母

        /// <summary>

        /// 是否加入小写字母

        /// </summary>

        private bool addLowerLetter = false;

        /// <summary>

        /// 是否加入小写字母(不包括o)

        /// </summary>

        public bool AddLowerLetter

        {

            get { return this.addLowerLetter; }

            set { this.addLowerLetter = value; }

        }

        #endregion

        #region 是否加入大写字母

        /// <summary>

        /// 是否加入大写字母

        /// </summary>

        private bool addUpperLetter = false;

        /// <summary>

        /// 是否加入大写字母(不包括O)

        /// </summary>

        public bool AddUpperLetter

        {

            get { return this.addUpperLetter; }

            set { this.addUpperLetter = value; }

        }

        #endregion

        #region 字体大小

        /// <summary>

        /// 字体大小

        /// </summary>

        private int fontSize = 18;

        /// <summary>

        /// 字体大小(默认为18)

        /// </summary>

        public int FontSize

        {

            get { return this.fontSize; }

            set { this.fontSize = value; }

        }

        #endregion

        #region 字体颜色

        /// <summary>

        /// 字体颜色

        /// </summary>

        private Color fontColor = Color.Blue;

        /// <summary>

        /// 字体颜色(默认为Blue)

        /// </summary>

        public Color FontColor

        {

            get { return this.fontColor; }

            set { this.fontColor = value; }

        }

        #endregion

        #region 字体类型

        /// <summary>

        /// 字体类型

        /// </summary>

        private string fontFamily = "Verdana";

        /// <summary>

        /// 字体类型(默认为Verdana)

        /// </summary>

        public string FontFamily

        {

            get { return this.fontFamily; }

            set { this.fontFamily = value; }

        }

        #endregion

        #region 背景色

        /// <summary>

        /// 背景色

        /// </summary>

        private Color backgroundColor = Color.AliceBlue;

        /// <summary>

        /// 背景色(默认为AliceBlue)

        /// </summary>

        public Color BackgroundColor

        {

            get { return this.backgroundColor; }

            set { this.backgroundColor = value; }

        }

        #endregion

        #region 前景噪点数量

        /// <summary>

        /// 前景噪点数量

        /// </summary>

        private int foreNoisePointCount = 2;

        /// <summary>

        /// 前景噪点数量(默认为2)

        /// </summary>

        public int ForeNoisePointCount

        {

            get { return this.foreNoisePointCount; }

            set { this.foreNoisePointCount = value; }

        }

        #endregion

        #region 随机码的旋转角度

        /// <summary>

        /// 随机码的旋转角度

        /// </summary>

        private int randomAngle = 45;

        /// <summary>

        /// 随机码的旋转角度(默认为40度)

        /// </summary>

        public int RandomAngle

        {

            get { return this.randomAngle; }

            set { this.randomAngle = value; }

        }

        #endregion

        #endregion

        #region Constructor Method

        /// <summary>

        /// 构造方法

        /// </summary>

        public Captcha()

        {

            this.GetText();

        }

        #endregion

        #region Private Method

        /// <summary>

        /// 得到验证码字符串

        /// </summary>

        private void GetText()

        {

            //没有外部输入验证码时随机生成

            if (String.IsNullOrEmpty(this.verifyCodeText))

            {

                StringBuilder objStringBuilder = new StringBuilder();

                //加入数字1-9

                for (int i = 1; i <= 9; i++)

                {

                    objStringBuilder.Append(i.ToString());

                }

                //加入大写字母A-Z，不包括O

                if (this.addUpperLetter)

                {

                    char temp = ' ';

                    for (int i = 0; i < 26; i++)

                    {

                        temp = Convert.ToChar(i + 65);

                        //如果生成的字母不是'O'

                        if (!temp.Equals('O'))

                        {

                            objStringBuilder.Append(temp);

                        }

                    }

                }

                //加入小写字母a-z，不包括o

                if (this.addLowerLetter)

                {

                    char temp = ' ';

                    for (int i = 0; i < 26; i++)

                    {

                        temp = Convert.ToChar(i + 97);

                        //如果生成的字母不是'o'

                        if (!temp.Equals('o'))

                        {

                            objStringBuilder.Append(temp);

                        }

                    }

                }

                //生成验证码字符串

                {

                    int index = 0;

                    for (int i = 0; i < length; i++)

                    {

                        index = objRandom.Next(0, objStringBuilder.Length);

                        this.verifyCodeText += objStringBuilder[index];

                        objStringBuilder.Remove(index, 1);

                    }

                }

            }

        }

        /// <summary>

        /// 得到验证码图片

        /// </summary>

        private Bitmap GetImage()

        {

            Bitmap result = null;

            //创建绘图

            result = new Bitmap(this.verifyCodeText.Length * 16, 25);

            using (Graphics objGraphics = Graphics.FromImage(result))

            {

                objGraphics.SmoothingMode = SmoothingMode.HighQuality;

                //清除整个绘图面并以指定背景色填充

                objGraphics.Clear(this.backgroundColor);

                //创建画笔

                using (SolidBrush objSolidBrush = new SolidBrush(this.fontColor))

                {

                    this.AddForeNoisePoint(result);

                    this.AddBackgroundNoisePoint(result, objGraphics);

                    //文字居中

                    StringFormat objStringFormat = new StringFormat(StringFormatFlags.NoClip);

                    objStringFormat.Alignment = StringAlignment.Center;

                    objStringFormat.LineAlignment = StringAlignment.Center;

                    //字体样式

                    Font objFont = new Font(this.fontFamily, objRandom.Next(this.fontSize - 3, this.fontSize), FontStyle.Regular);

                    //验证码旋转，防止机器识别

                    char[] chars = this.verifyCodeText.ToCharArray();

                    for (int i = 0; i < chars.Length; i++)

                    {

                        //转动的度数

                        float angle = objRandom.Next(-this.randomAngle, this.randomAngle);

                        objGraphics.TranslateTransform(12, 12);

                        objGraphics.RotateTransform(angle);

                        objGraphics.DrawString(chars[i].ToString(), objFont, objSolidBrush, -2, 2, objStringFormat);

                        objGraphics.RotateTransform(-angle);

                        objGraphics.TranslateTransform(2, -12);

                    }

                }

            }

            return result;

        }

        /// <summary>

        /// 添加前景噪点

        /// </summary>

        /// <param name="objBitmap"></param>

        private void AddForeNoisePoint(Bitmap objBitmap)

        {

            for (int i = 0; i < objBitmap.Width * this.foreNoisePointCount; i++)

            {

                objBitmap.SetPixel(objRandom.Next(objBitmap.Width), objRandom.Next(objBitmap.Height), this.fontColor);

            }

        }

        /// <summary>

        /// 添加背景噪点

        /// </summary>

        /// <param name="objBitmap"></param>

        /// <param name="objGraphics"></param>

        private void AddBackgroundNoisePoint(Bitmap objBitmap, Graphics objGraphics)

        {

            using (Pen objPen = new Pen(Color.Azure, 0))

            {

                for (int i = 0; i < objBitmap.Width * 2; i++)

                {

                    objGraphics.DrawRectangle(objPen, objRandom.Next(objBitmap.Width), objRandom.Next(objBitmap.Height), 1, 1);

                }

            }

        }

        #endregion

        #region Public Method

        public void Output(HttpResponse objHttpResponse)

        {

            using (Bitmap objBitmap = this.GetImage())

            {

                if (objBitmap != null)

                {

                    using (MemoryStream objMS = new MemoryStream())

                    {

                        objBitmap.Save(objMS, ImageFormat.Jpeg);

                        HttpContext.Current.Response.ClearContent();

                        HttpContext.Current.Response.ContentType = "image/Jpeg";

                        HttpContext.Current.Response.BinaryWrite(objMS.ToArray());

                        HttpContext.Current.Response.Flush();

                        HttpContext.Current.Response.End();

                    }

                }

            }

        }

        #endregion

    }

}