using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Drawing;using System.Drawing.Drawing2D;using System.Drawing.Imaging;using System.IO;/// <summary>///BitmapImage 的摘要說明/// </summary>public class BitmapImage{    public static MemoryStream ImageCheck()    {        Random random = new Random();        //隨機產生4位隨機數        string checkCode = random.Next(1000, 9999).ToString();        //Bitmap是用來指定初始化時文本的大小        Bitmap image = new Bitmap((int)Math.Ceiling((checkCode.Length * 20.5)), 22);        Graphics g = Graphics.FromImage(image);        try        {            g.Clear(Color.White);//清空圖片背景色            //畫圖片的背景噪音線這里是4條線            for (int i = 0; i < 4; 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.Black), x1, x2, y1, y2);            }            Font font = new Font("Arial", 12, FontStyle.Bold);            //設置顏色，起始位置等參數            LinearGradientBrush brush = new 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()));            }            //畫圖片噪音線            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);            MemoryStream ms = new MemoryStream();            image.Save(ms, ImageFormat.Gif);            return ms;        }        finally        {            g.Dispose();            image.Dispose();        }    }}

using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;using System.IO;public partial class _Default : System.Web.UI.Page{    PRotected void Page_Load(object sender, EventArgs e)    {        MemoryStream ms= BitmapImage.ImageCheck();        Response.ClearContent();        Response.ContentType = "image/Gif";        Response.BinaryWrite(ms.ToArray());    }}