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 }}原文：http://www.cnblogs.com/tianxuan/p/4733419.html