生成圖片的驗證碼

   private string GetRandCode(int num)
        {
        string[] code = new string[]{"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"};
        string vNum ="";
        Random ran = new Random();
        int iNum = 0;
        for (int i = 1; i <= num; i++)
        {
            //while((iNum = Convert.ToInt32(code.Length*ran.NextDouble())) == code.Length)
            //{
            //    iNum = Convert.ToInt32(code.Length*ran.NextDouble());
            //}
            iNum = ran.Next(0, code.Length);//哈哈 这句效率更高
            vNum +=code[iNum];
        }
        return vNum;
        }

        private void DrawImage(string code)
        {
        Bitmap bp = new Bitmap(60,25);
        Graphics ga = Graphics.FromImage(bp);
        ///设置画笔的输出模式
        ga.SmoothingMode = SmoothingMode.HighSpeed;

        Rectangle rc=new Rectangle(0,0,60,25);//定义一个矩形
        ga.FillRectangle(new SolidBrush(Color.White), rc);//填充矩形
        ga.DrawString(code, new Font("宋体", 16), new SolidBrush(Color.Red), rc);//在矩形内画出字符串
        Response.ContentType = "image/jpeg";

        //保存数据流
        bp.Save(Response.OutputStream,ImageFormat.Jpeg);
        bp.Dispose();
        ga.Dispose();
        } 

 

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