randomimage.aspx.cs

投票系统模块设计

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.IO;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;

namespace book07
{
	/// <summary>
	/// RandomImage 的摘要说明。
	/// </summary>
	public class RandomImage : System.Web.UI.Page
	{
		private void Page_Load(object sender, System.EventArgs e)
		{
			//输出带有随机校验码的图片
			CreateCheckCodeImage(GenerateCheckCode());
		}

		#region Web 窗体设计器生成的代码
		override protected void OnInit(EventArgs e)
		{
			//
			// CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。
			//
			InitializeComponent();
			base.OnInit(e);
		}
		
		/// <summary>
		/// 设计器支持所需的方法 - 不要使用代码编辑器修改
		/// 此方法的内容。
		/// </summary>
		private void InitializeComponent()
		{    
			this.Load += new System.EventHandler(this.Page_Load);
		}
		#endregion

		/// <summary>
		/// 生成随机校验码字符串
		/// </summary>
		/// <returns>生成的随机校验码字符串</returns>
		private string GenerateCheckCode()
		{
			int number;
			string strCode = string.Empty;

			//随机数种子
			Random random = new Random();

			for(int i = 0;i < 4;i++) //校验码长度为4
			{
				//随机的整数
				number = random.Next();

				//字符从0-9,A-Z中随机产生,对应的ASCII码分别为
				//48-57,65-90
				number = number % 36;				
				if (number < 10)
				{
					number += 48;
				}
				else
				{
					number += 55;
				}

				strCode += ((char)number).ToString();
			}

			//在Cookie中保存校验码
			Response.Cookies.Add(new HttpCookie("CheckCode", strCode));
			return strCode;
		}

		/// <summary>
		/// 根据校验码输出图片
		/// </summary>
		/// <param name="checkCode">产生的随机校验码</param>
		private void CreateCheckCodeImage(string checkCode)
		{
			//若校验码为空，则直接返回
			if(checkCode == null || checkCode.Trim() == String.Empty)
				return;

			//根据校验码的长度确定输出图片的长度
			System.Drawing.Bitmap image = new System.Drawing.Bitmap(
				(int)Math.Ceiling((checkCode.Length * 15)), 20);

			//创建Graphics对象
			Graphics g = Graphics.FromImage(image);

			try
			{
				//生成随机数种子
				Random random = new Random();

				//清空图片背景色
				g.Clear(Color.White);

				//画图片的背景噪音线 10条
				for(int i = 0;i < 10;i++)
				{
					//噪音线起点坐标(x1,y1),终点坐标(x2,y2)
					int x1 = random.Next(image.Width);
					int x2 = random.Next(image.Width);
					int y1 = random.Next(image.Height);
					int y2 = random.Next(image.Height);

					//用银色画出噪音线
					g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
				}

				//输出图片中校验码的字体: 12号Arial,粗斜体
				Font font = new Font(
					"Arial",
					12,
					(FontStyle.Bold | FontStyle.Italic) );

				//线性渐变画刷
				LinearGradientBrush brush = new LinearGradientBrush(
					new Rectangle(0, 0, image.Width, image.Height),
					Color.Blue,
					Color.Purple,
					1.2f,
					true );
				g.DrawString(checkCode, font, brush, 2, 2);

				//画图片的前景噪音点 50个
				for(int i = 0; i < 50;i++)
				{
					int x = random.Next(image.Width);
					int y = random.Next(image.Height);

					image.SetPixel(x, y, Color.FromArgb(random.Next()));
				}

				//画图片的边框线
				g.DrawRectangle(
					new Pen(Color.SaddleBrown),
					0,
					0,
					image.Width - 1,
					image.Height - 1 );

				//创建内存流用于输出图片
				using (MemoryStream ms = new MemoryStream())
				{
					//图片格式指定为png
					image.Save(ms, ImageFormat.Png);

					//清除缓冲区流中的所有输出
					Response.ClearContent();

					//输出流的HTTP MIME类型设置为"image/Png"
					Response.ContentType = "image/Png";

					//输出图片的二进制流
					Response.BinaryWrite(ms.ToArray());
				}
			}
			finally
			{
				//释放Bitmap对象和Graphics对象
				g.Dispose();
				image.Dispose();				
			}
		}

	}
}