控制验证码的位置

Question

我建了一个画布，画验证码，怎么固定验证码的位置，请问下？和怎么选择画布的背景颜色？
           context.Response.ContentType = "text/JPEG";
            //context.Response.Write("Hello World");
            using (System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap(100, 50))
            {
                using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap))
                {
                    Random rand = new Random();
                    int code = rand.Next(1000,9999);//随机产生验证码
                    string strCode = code.ToString();
                    //如果在一般处理程序中操作Session,就必须调用IRequiresSessionState 接口
                    HttpContext .Current .Session ["Code"]=strCode ;//创建一个Session对象，将验证码放入Session中
                    g.DrawString(strCode,new System.Drawing.Font("宋",20),System .Drawing .Brushes .Red ,new System .Drawing .PointF (0,0));
                    bitmap .Save (context .Response .OutputStream ,System .Drawing.Imaging .ImageFormat .Jpeg);
                }
            }
如果画布的宽度和高度大了，画出来的验证码很不好看的，它默认为居左对齐。

Answer 1

private String GenerateCheckCode() //产生验证码
    {
        int number;
        char code;
        string checkCode = String.Empty;
        System.Random random = new Random();
        for (int i = 0; i < 4; i++)
        {
            number = random.Next();
            if (number % 2 == 0)
                code = (char)('0' + (char)(number % 10));
            else
                code = (char)('A' + (char)(number % 26));
            checkCode += code.ToString();
 
        }
        Session["CheckCode"] = checkCode;
        return checkCode;
    }
    private void CreateCheckCodeImage(string checkCode)//用于产生背景图像
    {
        if (checkCode == null || checkCode.Trim() == String.Empty)
            return;
        System.Drawing.Bitmap image = new Bitmap(150, 50);
 
        Graphics g = Graphics.FromImage(image);
        try
        {
            //生成随即生成器;
            Random random = new Random();
            //清空图片背景色
            g.Clear(Color.White);
            //画图的背景噪音线
            for (int i = 0; i < 25; i++)
            {
                int x1 = random.Next(image.Width);
                int x2 = random.Next(image.Width);
                int y1 = random.Next(image.Width);
                int y2 = random.Next(image.Width);
                g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
 
            }
            Font font = new System.Drawing.Font("Arial", 40, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
            System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(
            new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
            g.DrawString(checkCode, font, brush, 2, 2);
            //图片的前景噪音点
            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()));
            }
            //画图片的前景噪音点
            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, System.Drawing.Imaging.ImageFormat.Gif);
            Response.ClearContent();
            Response.ContentType = "image/Gif";
            Response.BinaryWrite(ms.ToArray());
        }
        finally
        {
           
            g.Dispose();
            image.Dispose();
        }
    }