验证图片生成详细简解

   我详细介绍验证图片的生成，显示简单的字符串显示，详细看以下代码：

public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "image/jpeg";
            //创建位图，并且给指定边框的宽高
           using (Image img=new Bitmap(80,25))
           {

              //创建画家对象，在img对象画字符串
               using (Graphics g=Graphics.FromImage(img))
               { 
                //设置位图的背景颜色，默认是黑色
                 g.Clear(Color.White);
                //设置验证码的宽高, img.Width-1, img.Height-1主要是背景颜色覆盖了边框线
                 g.DrawRectangle(Pens.Black, 0, 0, img.Width-1, img.Height-1);
                   //传100个噪点，传画家对象，位图对象
                 DrawPoint(100, g, img);
               //画4个验证码的字符串
               string vcode=GetCode(4);//vcode这里可以赋值给Cookie

             g.DrawString(vcode,
              new Font("Arial", 14, FontStyle.Strikeout | FontStyle.Strikeout), // FontStyle字体的样式，多个样式，需要|线          

                Brushes.Black,
                   new RectangleF(r.Next(20), r.Next(7), img.Width, img.Height));
               img.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);//保存验证码对象，指定是Jpeg格式

               }
           }
        }

     //画噪点方法

        void DrawPoint(int point,Graphics g,Image img)
        {
            for (int i = 0; i < point; i++)
            {
                int x = r.Next(img.Width);
                int y = r.Next(img.Width);
                g.DrawLine(Pens.Red,
                    new Point(x, y),
                    new Point(x+2, y+2));

            }
        }

       //随机数
        Random r = new Random();

      //画字符创
        string GetCode(int point)
        {
            string txtStr = "ASF2345WE5R9F3HMBCZ455K";//这里的string字符串将会转成 char数组，阿拉伯数字1和小写字母l最好别写在里面，会搞胡乱。
            char[] charArr = txtStr.ToArray();
            int num = 0;
            string code = "";
            for (int i = 0; i <point; i++)
            {
                num = r.Next(charArr.Length);
                code +=charArr[num];
            }
            return code;
        }