C#生成图形验证码

先看效果：

再上代码

public class CaptchaHelper
	{
		private static Random rand = new Random();
		private static int previousAngle = 0;

		/// <summary>
		/// 生成图形验证码
		/// </summary>
		/// <returns></returns>
		public static byte[] Create(int codeLength, int width, int height, int fontSize, out String code)
		{
			String sCode = String.Empty;
			//可用颜色列表
			Color[] oColors = {
				 Color.FromArgb(118, 199, 192),
				 Color.FromArgb(97, 216, 206),
				 Color.FromArgb(84, 176, 168),
				 Color.FromArgb(117, 226, 217),
				 Color.FromArgb(43, 205, 191)
				 //Color.Red,
				 //Color.Blue,
				 //Color.Green,
				 //Color.Orange,
				 //Color.Brown,
				 //Color.Brown,
				 //Color.DarkBlue
				};
			//可用字体列表
			string[] oFontNames = { "Times New Roman", "MS Mincho", "Book Antiqua", "Gungsuh", "PMingLiU", "Impact" };
			//可用字符列表
			char[] oCharacter = {
			   '2','3','4','5','6','8','9',
			   'A','B','C','D','E','F','G','H','J','K','L','M','N','P','R','S','T','W','X','Y'
			  };
			//Random oRnd = new Random();
			Bitmap oBmp = null;
			Graphics oGraphics = null;
			int N1 = 0;
			Point oPoint1 = default(Point);
			Point oPoint2 = default(Point);
			string sFontName = null;
			Font oFont = null;
			Color oColor = default(Color);

			//生成验证码字符串
			for (N1 = 0; N1 <= codeLength - 1; N1++)
			{
				sCode += oCharacter[rand.Next(oCharacter.Length)];
			}

			oBmp = new Bitmap(width, height);
			oGraphics = Graphics.FromImage(oBmp);
			oGraphics.Clear(Color.White);
			try
			{
				for (N1 = 0; N1 <= 2; N1++)
				{
					//画噪线
					oPoint1.X = rand.Next(width);
					oPoint1.Y = rand.Next(height);
					oPoint2.X = rand.Next(width);
					oPoint2.Y = rand.Next(height);
					oColor = oColors[rand.Next(oColors.Length)];
					oGraphics.DrawLine(new Pen(oColor), oPoint1, oPoint2);
				}

				float spaceWith = 0, dotX = 0;
				if (codeLength != 0)
				{
					spaceWith = (width - fontSize * codeLength - 10) / codeLength;
				}

				for (N1 = 0; N1 <= sCode.Length - 1; N1++)
				{
					//画验证字符串
					sFontName = oFontNames[rand.Next(oFontNames.Length)];
					oFont = new Font(sFontName, fontSize, FontStyle.Bold);
					oColor = oColors[rand.Next(oColors.Length)];
					
					dotX = Convert.ToSingle(N1) * fontSize + (N1 + 1) * spaceWith;
					DrawCharacter(sCode[N1].ToString(), oGraphics, oFont, new SolidBrush(oColor), (int)dotX, fontSize, height);
				}

				for (int i = 0; i <= 30; i++)
				{
					//画噪点
					int x = rand.Next(oBmp.Width);
					int y = rand.Next(oBmp.Height);
					Color clr = oColors[rand.Next(oColors.Length)];
					oBmp.SetPixel(x, y, clr);
				}

				code = sCode;
				//保存图片数据
				MemoryStream stream = new MemoryStream();
				oBmp.Save(stream, ImageFormat.Jpeg);
				//输出图片流
				return stream.ToArray();
			}
			finally
			{
				oGraphics.Dispose();
			}
		}

		private static void DrawCharacter(string txt, Graphics gr, Font font, Brush brush,  int x, int charWidth, int height)
		{
			// 文字居中
			using (StringFormat stringFormat = new StringFormat())
			{
				stringFormat.Alignment = StringAlignment.Center;
				stringFormat.LineAlignment = StringAlignment.Center;
				RectangleF rectf = new RectangleF(x, 0, charWidth, height);

				// 转换为 Path
				using (GraphicsPath graphicsPath = new GraphicsPath())
				{
					graphicsPath.AddString(txt, font.FontFamily, (int)(font.Style), font.Size, rectf, stringFormat);					

					// 旋转一个随机角度
					float dx = (float)(x + charWidth / 2);
					float dy = (float)(height / 2);
					gr.TranslateTransform(-dx, -dy, MatrixOrder.Append);
					int angle = previousAngle;
					do
					{
						angle = rand.Next(-30, 30);
					} while (Math.Abs(angle - previousAngle) < 20);
					previousAngle = angle;
					gr.RotateTransform(angle, MatrixOrder.Append);
					gr.TranslateTransform(dx, dy, MatrixOrder.Append);

					// 画文字
					gr.FillPath(brush, graphicsPath);
					gr.ResetTransform();
				}
			}
		}
	}