BinaryWrite方法输出验证码

在创建网站中验证码是不可或缺的。可以利用BinaryWrite输出二进制图像的方法输出验证码。

在开发图形验证码时，首先生成验证码，然后绘制成图像，最后通过该方法输出到页面中。所以熟练地掌握该方法可以为以后开发图形验证码奠定基础。首先定义个字符串数组，随机去除一个用来做验证码。根据字符串长度创建一个画布Bitmap，接着在Bitmap对象上绘制边框，背景颜色，背景噪音线和前景噪音线，并且将绘制后的二进制图像保存到内存流中，最后通过Response对象的BinaryWrite方法输出到浏览器中。代码如下

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        //生成随机生成器
        Random random = new Random();
        //成语字符串数组，随机去除创建验证码
        string[] str = { "海阔天高", "望子成龙", "守株待兔", "国足无敌", "点石成金", "天涯明月", "尧尧无敌", "一望无际" };
        //string checkCode = "海阔天高";
        int count = random.Next(str.Length);
        string checkCode = str[count];
        //根据字符串长度创建一个Bitmap画布
        Bitmap image = new Bitmap((int)Math.Ceiling((checkCode.Length * 20.5)), 22);
        Graphics g = Graphics.FromImage(image);
        try
        {
            g.Clear(Color.White);//清空图片背景色
            for (int i = 0; i < 2; i++)//生成两条随机的噪音线
            {
                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, y1, x2, y2);
            }
            Font font = new Font("Arial", 12, (FontStyle.Bold));//定义字体
            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);
            //画图片前景噪音点
            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()));
            }
            //画图片边框线
            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, ImageFormat.Gif);
            Response.ClearContent();
            Response.ContentType = "image/Gif";
            Response.BinaryWrite(ms.ToArray());
        }
        finally
        {
            g.Dispose();
            image.Dispose();
        }
    }
}