验证码定义：
就是将一串随机产生的数字或符号，生成一幅图片，图片里加上一些干扰象素（防止OCR），由用户肉眼识别其中的验证码信息，输入表单提交网站验证，验证成功后才能使用某项功能
项目中，我们登录注册都会用到验证码，那为什么我们要使用验证码呢？
经过资料查询以及个人理解，验证码的作用：防止批量进行一些操作：例如贴吧，论坛中匿名发帖，针对某特定用户用特殊破解方式登录尝试，防止机器恶意注册等
在C#中，代码如下：
try
{
Response.Cache.SetCacheability(HttpCacheability.NoCache);
string randomcode = Globals.CreateVerifyCode(4);
// 随机转动角度
int randAngle = 45;
int mapwidth = (int)(randomcode.Length * 33);
// 创建图片背景
Bitmap map = new Bitmap(mapwidth-5, 45);
Graphics graph = Graphics.FromImage(map);
// 清除画面，填充背景
graph.Clear(Color.AliceBlue);
// 画一个边框
//graph.DrawRectangle(new Pen(Color.Gray, 0), 0, 0, map.Width-1, map.Height - 3);
//graph.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;//模式
Random rand = new Random();
// 背景噪点生成
Pen blackPen = new Pen(Color.LightGray, 0);
for (int i = 0; i < 50; i++)
{
int x = rand.Next(0, map.Width);
int y = rand.Next(0, map.Height);
graph.DrawRectangle(blackPen, x, y, 1, 1);
}
// 验证码旋转，防止机器识别
// 拆散字符串成单字符数组
char[] chars = randomcode.ToCharArray();
// 文字距中
StringFormat format = new StringFormat(StringFormatFlags.NoClip);
format.Alignment = StringAlignment.Center;
format.LineAlignment = StringAlignment.Center;
// 定义颜色
Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Brown, Color.DarkCyan, Color.Purple,Color.DarkGreen };
// 定义字体
//string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial","Lucida Sans Unicode", Rockwell, Batang ,Times New Roman,Bernard MT Condensed};
for (int i = 0; i < chars.Length; i++)
{
int cindex = rand.Next(7);
int findex = rand.Next(4);
// 字体样式(参数2为字体大小)
Font f = new System.Drawing.Font("Microsoft Sans Serif", 17, System.Drawing.FontStyle.Bold);
Brush b = new System.Drawing.SolidBrush(c[cindex]);
Point dot = new Point(23, 15);
// 测试X坐标显示间距的
//graph.DrawString(dot.X.ToString(),fontstyle,new SolidBrush(Color.Black),10,150);
// 转动的度数
float angle = rand.Next(-randAngle, randAngle);
// 移动光标到指定位置
graph.TranslateTransform(dot.X, dot.Y);
graph.RotateTransform(angle);
graph.DrawString(chars[i].ToString(), f, b, 1, 10, format);
//graph.DrawString(chars[i].ToString(),fontstyle,new SolidBrush(Color.Blue),1,1,format);
// 转回去
graph.RotateTransform(-angle);
// 移动光标到指定位置
graph.TranslateTransform(3, -dot.Y);
}
// 标准随机码
//graph.DrawString(randomcode,fontstyle,new SolidBrush(Color.Blue),2,2);
// 生成图片
System.IO.MemoryStream ms = new System.IO.MemoryStream();
map.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
Response.ClearContent();
Response.ContentType = "image/gif";
Response.BinaryWrite(ms.ToArray());
graph.Dispose();
map.Dispose();
}
catch
{
}
或者我们还有更全的方法实现：
namespace DotNet.Utilities { /// <summary> /// 验证码类 /// </summary> public class Rand { #region 生成随机数字 /// <summary> /// 生成随机数字 /// </summary> /// <param name="length">生成长度</param> public static string Number(int Length) { return Number(Length, false); } /// <summary> /// 生成随机数字 /// </summary> /// <param name="Length">生成长度</param> /// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param> public static string Number(int Length, bool Sleep) { if (Sleep) System.Threading.Thread.Sleep(3); string result = ""; System.Random random = new Random(); for (int i = 0; i < Length; i++) { result += random.Next(10).ToString(); } return result; } #endregion #region 生成随机字母与数字 /// <summary> /// 生成随机字母与数字 /// </summary> /// <param name="IntStr">生成长度</param> public static string Str(int Length) { return Str(Length, false); } /// <summary> /// 生成随机字母与数字 /// </summary> /// <param name="Length">生成长度</param> /// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param> public static string Str(int Length, bool Sleep) { if (Sleep) System.Threading.Thread.Sleep(3); char[] Pattern = new char[] { '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', 'V', 'W', 'X', 'Y', 'Z' }; string result = ""; int n = Pattern.Length; System.Random random = new Random(~unchecked((int)DateTime.Now.Ticks)); for (int i = 0; i < Length; i++) { int rnd = random.Next(0, n); result += Pattern[rnd]; } return result; } #endregion #region 生成随机纯字母随机数 /// <summary> /// 生成随机纯字母随机数 /// </summary> /// <param name="IntStr">生成长度</param> public static string Str_char(int Length) { return Str_char(Length, false); } /// <summary> /// 生成随机纯字母随机数 /// </summary> /// <param name="Length">生成长度</param> /// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param> public static string Str_char(int Length, bool Sleep) { if (Sleep) System.Threading.Thread.Sleep(3); char[] Pattern = new char[] { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' }; string result = ""; int n = Pattern.Length; System.Random random = new Random(~unchecked((int)DateTime.Now.Ticks)); for (int i = 0; i < Length; i++) { int rnd = random.Next(0, n); result += Pattern[rnd]; } return result; } #endregion } /// <summary> /// 验证图片类 /// </summary> public class YZMHelper { #region 私有字段 private string text; private Bitmap image; private int letterCount = 4; //验证码位数 private int letterWidth = 16; //单个字体的宽度范围 private int letterHeight = 20; //单个字体的高度范围 private static byte[] randb = new byte[4]; private static RNGCryptoServiceProvider rand = new RNGCryptoServiceProvider(); private Font[] fonts = { new Font(new FontFamily("Times New Roman"),10 +Next(1),System.Drawing.FontStyle.Regular), new Font(new FontFamily("Georgia"), 10 + Next(1),System.Drawing.FontStyle.Regular), new Font(new FontFamily("Arial"), 10 + Next(1),System.Drawing.FontStyle.Regular), new Font(new FontFamily("Comic Sans MS"), 10 + Next(1),System.Drawing.FontStyle.Regular) }; #endregion #region 公有属性 /// <summary> /// 验证码 /// </summary> public string Text { get { return this.text; } } /// <summary> /// 验证码图片 /// </summary> public Bitmap Image { get { return this.image; } } #endregion #region 构造函数 public YZMHelper() { HttpContext.Current.Response.Expires = 0; HttpContext.Current.Response.Buffer = true; HttpContext.Current.Response.ExpiresAbsolute = DateTime.Now.AddSeconds(-1); HttpContext.Current.Response.AddHeader("pragma", "no-cache"); HttpContext.Current.Response.CacheControl = "no-cache"; this.text = Rand.Number(4); CreateImage(); } #endregion #region 私有方法 /// <summary> /// 获得下一个随机数 /// </summary> /// <param name="max">最大值</param> private static int Next(int max) { rand.GetBytes(randb); int value = BitConverter.ToInt32(randb, 0); value = value % (max + 1); if (value < 0) value = -value; return value; } /// <summary> /// 获得下一个随机数 /// </summary> /// <param name="min">最小值</param> /// <param name="max">最大值</param> private static int Next(int min, int max) { int value = Next(max - min) + min; return value; } #endregion #region 公共方法 /// <summary> /// 绘制验证码 /// </summary> public void CreateImage() { int int_ImageWidth = this.text.Length * letterWidth; Bitmap image = new Bitmap(int_ImageWidth, letterHeight); Graphics g = Graphics.FromImage(image); g.Clear(Color.White); for (int i = 0; i < 2; i++) { int x1 = Next(image.Width - 1); int x2 = Next(image.Width - 1); int y1 = Next(image.Height - 1); int y2 = Next(image.Height - 1); g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2); } int _x = -12, _y = 0; for (int int_index = 0; int_index < this.text.Length; int_index++) { _x += Next(12, 16); _y = Next(-2, 2); string str_char = this.text.Substring(int_index, 1); str_char = Next(1) == 1 ? str_char.ToLower() : str_char.ToUpper(); Brush newBrush = new SolidBrush(GetRandomColor()); Point thePos = new Point(_x, _y); g.DrawString(str_char, fonts[Next(fonts.Length - 1)], newBrush, thePos); } for (int i = 0; i < 10; i++) { int x = Next(image.Width - 1); int y = Next(image.Height - 1); image.SetPixel(x, y, Color.FromArgb(Next(0, 255), Next(0, 255), Next(0, 255))); } image = TwistImage(image, true, Next(1, 3), Next(4, 6)); g.DrawRectangle(new Pen(Color.LightGray, 1), 0, 0, int_ImageWidth - 1, (letterHeight - 1)); this.image = image; } /// <summary> /// 字体随机颜色 /// </summary> public Color GetRandomColor() { Random RandomNum_First = new Random((int)DateTime.Now.Ticks); System.Threading.Thread.Sleep(RandomNum_First.Next(50)); Random RandomNum_Sencond = new Random((int)DateTime.Now.Ticks); int int_Red = RandomNum_First.Next(180); int int_Green = RandomNum_Sencond.Next(180); int int_Blue = (int_Red + int_Green > 300) ? 0 : 400 - int_Red - int_Green; int_Blue = (int_Blue > 255) ? 255 : int_Blue; return Color.FromArgb(int_Red, int_Green, int_Blue); } /// <summary> /// 正弦曲线Wave扭曲图片 /// </summary> /// <param name="srcBmp">图片路径</param> /// <param name="bXDir">如果扭曲则选择为True</param> /// <param name="nMultValue">波形的幅度倍数，越大扭曲的程度越高,一般为3</param> /// <param name="dPhase">波形的起始相位,取值区间[0-2*PI)</param> public System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase) { double PI = 6.283185307179586476925286766559; Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height); Graphics graph = Graphics.FromImage(destBmp); graph.FillRectangle(new SolidBrush(Color.White), 0, 0, destBmp.Width, destBmp.Height); graph.Dispose(); double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width; for (int i = 0; i < destBmp.Width; i++) { for (int j = 0; j < destBmp.Height; j++) { double dx = 0; dx = bXDir ? (PI * (double)j) / dBaseAxisLen : (PI * (double)i) / dBaseAxisLen; dx += dPhase; double dy = Math.Sin(dx); int nOldX = 0, nOldY = 0; nOldX = bXDir ? i + (int)(dy * dMultValue) : i; nOldY = bXDir ? j : j + (int)(dy * dMultValue); Color color = srcBmp.GetPixel(i, j); if (nOldX >= 0 && nOldX < destBmp.Width && nOldY >= 0 && nOldY < destBmp.Height) { destBmp.SetPixel(nOldX, nOldY, color); } } } srcBmp.Dispose(); return destBmp; } #endregion } }
我们将生成的验证码中的字符串存如session或者cookies中，在onclick事件中获取session或者cookies值与用户输入的值进行匹配即可。
/// <summary> ///创建验证码 /// </summary> public class CreateIdentifyingCode { /// <summary> /// 生成随机字符串 /// </summary> /// <param name="codeCount"></param> /// <returns></returns> public string CreateRandomCode(int codeCount) { string randomCode = ""; try { string allChar = "2,3,4,5,6,7,H,J,K,L,M,N,X,Y,Z,a,b,c,d,e,f,g,h,i,j,k,m,n,p,q,P,Q,R,S,T,U,V,W,r,s,t,u,v,8,9,A,B,C,D,E,F,G,w,x,y,z"; //按 ,号拆分字符串 string[] allCharArray = allChar.Split(','); int temp = -1; Random rand = new Random(); for (int i = 0; i < codeCount; i++) { if (temp > 0) { rand = new Random(1 * temp * ((int)DateTime.Now.Ticks)); } int t = rand.Next(35); if (temp == t) { return CreateRandomCode(codeCount); } temp = t; randomCode += allCharArray[t]; } } catch (Exception) { } return randomCode; } /// <summary> /// 创建验证码图片,并保存 /// </summary> /// <param name="validateCode"></param> /// <returns></returns> public void SaveValidateGraphic(string validateCode, string path) { byte[] buffer = CreateValidateGraphic(validateCode); MemoryStream ms2 = new MemoryStream(buffer, 0, buffer.Length); ms2.Seek(0, SeekOrigin.Begin); System.Drawing.Image image2 = System.Drawing.Image.FromStream(ms2); image2.Save(path + "x.jpg", ImageFormat.Jpeg); } /// <summary> /// 创建验证码图片 /// </summary> /// <param name="validateCode"></param> /// <returns></returns> public byte[] CreateValidateGraphic(string validateCode) { //设置图片的宽度与高度 Bitmap image = new Bitmap((int)Math.Ceiling(validateCode.Length * 16.0), 27); Graphics g = Graphics.FromImage(image); try { //生成随机生成器 Random random = new Random(); //清空图片背景色 g.Clear(Color.White); //图片的干扰线 for (int i = 0; i < 50; i++) { int x1 = random.Next(image.Width); int x2 = random.Next(image.Width); int y1 = random.Next(image.Width); int y2 = random.Next(image.Width); g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2); } Font font = new Font("Arial", 13, (FontStyle.Bold | FontStyle.Italic)); LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true); g.DrawString(validateCode, font, brush, 3, 2); //画图片的前景干扰点 for (int i = 0; i < 100; i++) { int x = random.Next(image.Width); int y = random.Next(image.Height); image.SetPixel(x, y, Color.FromArgb(random.Next())); } //画图片的干扰线 g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1); //保存图片数据 MemoryStream stream = new MemoryStream(); image.Save(stream, ImageFormat.Jpeg); //输出图片流 return stream.ToArray(); } finally { g.Dispose(); image.Dispose(); } } }
很简单的实用的验证码就介绍到这里，有什么不足的还请大家多多指导。