using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;

namespace ChatRoom
{
	/// <summary>
	/// ValidateCode 的摘要說明。
	/// </summary>
	public class ValidateCode : System.Web.UI.Page
	{
		private void Page_Load(object sender, System.EventArgs e)
		{
			this.CreateCheckCodeImage(GenerateCheckCode());
		}

		#region Web 窗體設計器生成的代碼
		override protected void OnInit(EventArgs e)
		{
			//
			// CODEGEN: 該調用是 ASP.NET Web 窗體設計器所必需的。
			//
			InitializeComponent();
			base.OnInit(e);
		}
  
		/// <summary>
		/// 設計器支持所需的方法 - 不要使用代碼編輯器修改
		/// 此方法的內容。
		/// </summary>
		private void InitializeComponent()
		{    
			this.Load += new System.EventHandler(this.Page_Load);
		}
		#endregion

		private string GenerateCheckCode()
		{
			int number;
			char code;
			string checkCode = String.Empty;

			System.Random random = new Random();

			for(int i=0; i<5; i++)
			{
				number = random.Next();

				//偶數生成數字，奇數生成字母
				if(number % 2 == 0)
					code = (char)('0' + (char)(number % 10));
				else
					code = (char)('A' + (char)(number % 26));

				checkCode += code.ToString();
			}

			Session.Add("CheckCode", checkCode);
			return checkCode;
		}

		private void CreateCheckCodeImage(string checkCode)
		{
			if(checkCode == null || checkCode.Trim() == String.Empty)
				return;

			//生成一個圖片，定義其寬和高
			System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
			Graphics g = Graphics.FromImage(image);

			try
			{
				//生成隨機生成器
				Random random = new Random();

				//清空圖片背景色
				g.Clear(Color.White);

				//畫圖片的背景噪音線
				for(int i=0; i<25; i++)
				{
					int x1 = random.Next(image.Width);
					int x2 = random.Next(image.Width);
					int y1 = random.Next(image.Height);
					int y2 = random.Next(image.Height);

					g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
				}

				Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
				System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
				g.DrawString(checkCode, font, brush, 2, 2);

				//畫圖片的前景噪音點
				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()));
				}

				//畫圖片的邊框線
				g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

				System.IO.MemoryStream ms = new System.IO.MemoryStream();
				image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
				Response.ClearContent();
				Response.ContentType = "image/Gif";
				Response.BinaryWrite(ms.ToArray());
				Response.End();
			}
			catch(Exception ex)
			{
				throw ex;
			}
			finally
			{
				g.Dispose();
				image.Dispose();
			}
		}
	}
}