随机验证码生成

public static void CreateValidateGraphic(string validateCode, HttpContext httpContext)
    {
        Bitmap img = new Bitmap((int)Math.Ceiling(validateCode.Length * 12.0), 20);
        Graphics g = Graphics.FromImage(img);
        try
        {
            Random random = new Random();
            g.Clear(Color.White);

            //图片的干扰线
            for (int i = 0; i < 25; i++)
            {
                int x1 = random.Next(img.Width);
                int x2 = random.Next(img.Width);
                int y1 = random.Next(img.Height);
                int y2 = random.Next(img.Height);
                g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
            }
            Font font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));
            System.Drawing.Drawing2D.LinearGradientBrush brush = new LinearGradientBrush(
                new Rectangle(0, 0, img.Width, img.Height), Color.Blue, Color.DarkRed, 1.2f, true);
            g.DrawString(validateCode, font, brush, 3, 2);
            //图片前景干扰点
            for (int i = 0; i < 100; i++)
            {
                int x = random.Next(img.Width);
                int y = random.Next(img.Height);
                img.SetPixel(x,y,Color.FromArgb(random.Next()));
                
            }
            //图片边框线
            g.DrawRectangle(new Pen(Color.Silver),0,0,img.Width-1,img.Height-1 );
            MemoryStream memoryStream=new MemoryStream();
            img.Save(memoryStream,ImageFormat.Jpeg);
            httpContext.Response.Clear();
            httpContext.Response.ContentType = "image/jpeg";
            httpContext.Response.BinaryWrite(memoryStream.ToArray());
        }
        catch (Exception)
        {

            throw;
        }
    }