Kim胖胖小小技術分享空間

最近寫的圖形驗證碼程式，提供大家參考。

using System;
using System.Web;
using System.Data;
using System.Drawing;

namespace Captcha
{
    /// 

    /// 圖形驗證碼
    /// 
    public class Captcha : IHttpHandler
    {
        int int_Red = 0, int_Green = 0, int_Blue = 0, int_Base = 0, int_Rand = 0;
        Random RandGen = new Random();
        int FontSize = 14;
        string[] aryFonts = new string[] { "Arial Black", "Verdana", "Comic Sans MS"
                    , "sans-serif", "Helvetica"};

        public void ProcessRequest(HttpContext context)
        {
			//依個人專案需求取得隨機亂碼
            string RandomCode = getRandomCode();

            CreateCheckCodeImage(RandomCode);
        }

        /// 

        /// 取得顏色
        /// 
        public Color getColor(int int_Base=0, int int_Rand=255)
        {
            int_Red = RandGen.Next(0, int_Rand) + int_Base;
            int_Green = RandGen.Next(0, int_Rand) + int_Base;
            int_Blue = RandGen.Next(0, int_Rand) + int_Base;

            return Color.FromArgb(int_Red, int_Green, int_Blue);
        }
        /// 

        /// 取得字型隨機顏色
        /// 
        public Color getFontColor()
        {
            int_Base = 30;
            int_Rand = 100;
            return getColor(int_Base, int_Rand);
        }
        /// 

        /// 取得中間隨機顏色
        /// 
        public Color getMidColor()
        {
            int_Base = 100;
            int_Rand = 100;
            return getColor(int_Base, int_Rand);
		}
		
        private void CreateCheckCodeImage(string checkCode)
	    {
            if (string.IsNullOrEmpty(checkCode))
			    return;

            int i = 0, x = 0, y = 0;
            FontStyle fontset = default(FontStyle);
            Font font = default(Font);
            System.Drawing.Drawing2D.LinearGradientBrush brush;
            Bitmap image = new Bitmap(checkCode.Length * 25, 30);
		    Graphics g = Graphics.FromImage(image);
            System.IO.MemoryStream ms = new System.IO.MemoryStream();

            try
            {
                //設定畫布底色
                g.Clear(Color.White);

                //背景斜線
                for (i = 0; i < 5; i++)
                    g.DrawLine(new Pen(getFontColor()), RandGen.Next(image.Width), RandGen.Next(image.Height)
                                    , RandGen.Next(image.Width), RandGen.Next(image.Height));

                for (i = 0; i < checkCode.Length; i++)
                {
                    //隨機樣式
                    switch (RandGen.Next(0, 2))
                    {
                        case 0:
                            fontset = FontStyle.Bold;
                            break;
                        case 1:
                            fontset = FontStyle.Italic;
                            break;
                        case 2:
                            fontset = FontStyle.Regular;
                            break;
                    }

                    //隨機字型
                    font = new Font(aryFonts[RandGen.Next(0, aryFonts.Length - 1)], FontSize, fontset);
                    
                    //隨機位移
                    x = (i * 22) + RandGen.Next(0, 10);
                    y = 1 + RandGen.Next(0, 3);
                    //產生隨機顏色的漸層筆刷
                    brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height)
                                                                                , getFontColor(), getMidColor(), 1.2f, true);
                    //依照設定畫出文字
                    g.DrawString(checkCode[i].ToString(), font, brush, x, y);
                }

                //在文字上放入干擾雜點
                for (i = 0; i < 100; i++)
                    image.SetPixel(RandGen.Next(image.Width), RandGen.Next(image.Height), getFontColor());

                //畫出方型外框
                g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
                
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Png);

                //設置無Cache
                HttpContext.Current.Response.ClearContent();
                HttpContext.Current.Response.Buffer=true;
                HttpContext.Current.Response.ExpiresAbsolute=DateTime.Now;
                HttpContext.Current.Response.Expires=0;
                HttpContext.Current.Response.AppendHeader("Pragma", "No-Cache");
                HttpContext.Current.Response.CacheControl="no-cache";
                HttpContext.Current.Response.ContentType = "image/Png";
                HttpContext.Current.Response.BinaryWrite(ms.ToArray());
            }
            catch
            {
                throw;
            }
            finally {
                ms.Close();
			    g.Dispose();
			    image.Dispose();
		    }
	    } 

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}