012. asp.net生成验证码图片(汉字示例/字母+数字)

    protected void Page_Load(object sender, EventArgs e)
    {
        //生成验证码图片的基本步骤
        string checkCode = "新年快乐";
        //定义画布大小
        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 20.5)), );
        //指定绘制类型
        Graphics g = Graphics.FromImage(image);
        try
        {
            //生成随机生成器
            Random random = new Random();
            //清空图片背景色
            g.Clear(Color.White);
            //画图片的背景噪音线
            for (int i = ; i < ; 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, y1, x2, y2);
            }
            //指定字体/字号/样式
            Font font = new System.Drawing.Font("Arial", , (System.Drawing.FontStyle.Bold));
            //指定画笔, 线性渐变
            System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(, , image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
            g.DrawString(checkCode, font, brush, , );
            //画图片的前景噪音点
            for (int i = ; i < ; i++)
            {
                int x = random.Next(image.Width);
                int y = random.Next(image.Height);
                image.SetPixel(x, y, Color.FromArgb(random.Next()));
            }
            //画图片的边框线
            g.DrawRectangle(new Pen(Color.Silver), , , image.Width - , image.Height - );
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            //将绘制的图片以指定的格式保存到内存中
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
            //清除缓存
            Response.ClearContent();
            //指定输出类型
            Response.ContentType = "image/Gif";
            //以二进制方式输出
            Response.BinaryWrite(ms.ToArray());
        }
        finally
        {
            g.Dispose();
            image.Dispose();
        }

    }

最终效果:

aaarticlea/png;base64,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" alt="" />

public partial class _Default : System.Web.UI.Page
{
    /// <summary>
    /// 生成随机数字符串, 并保存到Cookie中
    /// </summary>
    /// <returns></returns>
    private string GenerateCheckCode()
    {
        int number;
        char code;
        string checkCode = String.Empty;
        Random random = new Random();
        for (int i = ; i < ; i++)
        {
            number = random.Next();
            if (number %  == )
                code = (char)('' + (char)(number % ));
            else
                code = (char)('A' + (char)(number % ));
            checkCode += code.ToString();
        }
        Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
        return checkCode;
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        string checkCode = GenerateCheckCode();
        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 13.3)), );
        Graphics g = Graphics.FromImage(image);
        try
        {
            //生成随机生成器
            Random random = new Random();
            //清空图片背景色
            g.Clear(Color.White);
            //画图片的背景噪音线
            for (int i = ; i < ; 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, y1, x2, y2);
            }
            Font font = new System.Drawing.Font("Arial", , (System.Drawing.FontStyle.Bold));
            System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(, , image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
            g.DrawString(checkCode, font, brush, , );
            //画图片的前景噪音点
            for (int i = ; i < ; i++)
            {
                int x = random.Next(image.Width);
                int y = random.Next(image.Height);
                image.SetPixel(x, y, Color.FromArgb(random.Next()));
            }
            //画图片的边框线
            g.DrawRectangle(new Pen(Color.Silver), , , image.Width - , image.Height - );
            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();
        }

    }
}

最终结果:

aaarticlea/png;base64,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" alt="" />