<ItemGroup>

     <PackageReference Include="sqlite-net-pcl" Version="1.8.116" />

     <PackageReference Include="SQLiteNetExtensions.Async" Version="2.1.0" />

     <PackageReference Include="SQLitePCLRaw.bundle_green" Version="2.1.4" />

     <PackageReference Include="SQLitePCLRaw.core" Version="2.1.4" />

     <PackageReference Include="SQLitePCLRaw.lib.e_sqlite3" Version="2.1.4" />

     <PackageReference Include="SQLitePCLRaw.provider.dynamic_cdecl" Version="2.1.4" />

     <PackageReference Include="System.Data.DataSetExtensions" Version="4.5.0" />

    </ItemGroup>

<a href="http://..." target="_blank" rel="opener">Link</a>

$(".hlkPrint").click(function () {

    $("form").setPostDataToStorage();



    $("form").attr("rel", "opener");

    $("form").attr("target", "_blank");

    $("form").attr("action", "xxxxx.aspx");

    $("form").submit();

}); 

        static List<Brush> CaptchaBrushes = null;

        public static FileStreamResult CreateCaptcha(string captcha)

        {

            if (CaptchaBrushes == null)

            {

                CaptchaBrushes = new List<Brush>();

                CaptchaBrushes.Add(Brushes.White);

                CaptchaBrushes.Add(Brushes.Gold);

                CaptchaBrushes.Add(Brushes.LightSkyBlue);

                CaptchaBrushes.Add(Brushes.LimeGreen);

                CaptchaBrushes.Add(Brushes.AliceBlue);

                CaptchaBrushes.Add(Brushes.AntiqueWhite);

                CaptchaBrushes.Add(Brushes.BurlyWood);

                CaptchaBrushes.Add(Brushes.Silver);

            }



            int width = 90;

            int height = 45;



            //https://stackoverflow.com/questions/61365732/cannot-access-a-closed-stream-when-returning-filestreamresult-from-c-sharp-netc

            //Using statements close and unload the variable from memory set in the using statement which is why you are getting an error trying to access a closed memory stream.You don't need to use a using statement if you are just going to return the result at the end.



            //這個 memory stream 不用關閉或 dispose

            var ms = new MemoryStream();



            // 釋放所有在 GDI+ 所佔用的記憶體空間 ( 非常重要!! )

            using (Bitmap _bmp = new Bitmap(width, height))

            using (Graphics _graphics = Graphics.FromImage(_bmp))

            using (Font _font = new Font("Courier New", 24, FontStyle.Bold)) // _font 設定要出現在圖片上的文字字型、大小與樣式

            {

                // (封裝 GDI+ 繪圖介面) 所有繪圖作業都需透過 Graphics 物件進行操作

                _graphics.Clear(Color.Black);



                // 如果想啟用「反鋸齒」功能，可以將以下這行取消註解

                //_graphics.TextRenderingHint = TextRenderingHint.AntiAlias;



                // 將亂碼字串「繪製」到之前產生的 Graphics 「繪圖板」上

                var x = 10;

                for(var i = 0; i < captcha.Length; i++)

                {

                    _graphics.DrawString(captcha.Substring(i, 1), _font, CaptchaBrushes[Su.MathUtil.GetRandomInt(CaptchaBrushes.Count)], x, Su.MathUtil.GetRandomInt(15));

                    x += 10 + Su.MathUtil.GetRandomInt(10);

                }



                // 畫線

                

                _graphics.DrawLine(new Pen(CaptchaBrushes[Su.MathUtil.GetRandomInt(CaptchaBrushes.Count)], 1),

                    Su.MathUtil.GetRandomInt(0, Convert.ToInt32((width * 0.9 / 2))), 0, Su.MathUtil.GetRandomInt(Convert.ToInt32(width / 2), Convert.ToInt32(width * 1.9 / 2)), height);

                

                _graphics.DrawLine(new Pen(CaptchaBrushes[Su.MathUtil.GetRandomInt(CaptchaBrushes.Count)], 1),

                    Su.MathUtil.GetRandomInt(Convert.ToInt32(width / 2), Convert.ToInt32(width * 1.9 / 2)), 0, Su.MathUtil.GetRandomInt(0, Convert.ToInt32((width * 0.9 / 2))), height);

                

                _graphics.DrawLine(new Pen(CaptchaBrushes[Su.MathUtil.GetRandomInt(CaptchaBrushes.Count)], 1),

                    0,

                    Su.MathUtil.GetRandomInt(height / 2),

                    width,

                    height / 2 + Su.MathUtil.GetRandomInt(height / 2)

                    );



                _graphics.DrawLine(new Pen(CaptchaBrushes[Su.MathUtil.GetRandomInt(CaptchaBrushes.Count)], 1),

                 0,

                 height / 2 + Su.MathUtil.GetRandomInt(height / 2),

                 width,

                    Su.MathUtil.GetRandomInt(height / 2)

                 );



                _bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);

            }



            ms.Seek(0, SeekOrigin.Begin);



            // Controller 的型別為 FileResult

            return new FileStreamResult(ms, "image/jpeg")

            { FileDownloadName = $"{DateTime.Now.Ymdhmsf()}.jpg" };

        }

namespace Web.Controllers

{

    public class CaptchaController : Controller

    {

        [Route("captcha")]

        public async Task<FileStreamResult> Index()

        {

            //產生 Captcha 並存入 Session 之中。目前是四位數字

            string captcha = (await Ah.ReGetAsync<object>("api/kol/create-captcha-code")).ToString();



            //產生圖檔並回傳 FileStreamResult

            return Su.Wu.CreateCaptcha(captcha);

        }

    }

}

        static System.Security.Cryptography.RandomNumberGenerator RandomNumberGenerator = null;



        /// <summary>

        /// 回傳大於等於 0 小於 1

        /// </summary>

        /// <returns></returns>

        public static double NextDouble()

        {

            if (RandomNumberGenerator == null || LastRandomGenerateTime < DateTime.Now.AddMinutes(-1))

            {

                RandomNumberGenerator = System.Security.Cryptography.RandomNumberGenerator.Create();

            }



            // Generate four random bytes

            byte[] four_bytes = new byte[4];

            RandomNumberGenerator.GetBytes(four_bytes);



            // Convert the bytes to a UInt32

            uint scale = BitConverter.ToUInt32(four_bytes, 0);



            // And use that to pick a random number >= min and < max

            // 0 <= (scale / (uint.MaxValue + 1.0)) < 1

            return scale / (uint.MaxValue + 1.0);

        }



        /// <summary>

        /// 回傳值介於 min ~ (max - 1)

        /// </summary>

        /// <param name="min"></param>

        /// <param name="max"></param>

        /// <returns></returns>

        public static int GetRandomInt(int min, int max)

        {

            if(max < min)

            {

                throw new Exception("最大值不可小於最小值");

            }



            // Generate four random bytes

            byte[] four_bytes = new byte[4];

            RandomNumberGenerator.GetBytes(four_bytes);



            // And use that to pick a random number >= min and < max

            return (int)(min + (max - min) * NextDouble()); //因為 NextDouble 會小於 1，所以用無條件捨去.

        }



        /// <summary>

        /// 產生 0 ~ (max - 1) 的亂數

        /// </summary>

        /// <param name="max"></param>

        /// <returns></returns>

        public static int GetRandomInt(int max)

        {

            return GetRandomInt(0, max);

        }



        /// <summary>

        /// 產生 0 ~ (int.MaxValue - 1) 的亂數

        /// </summary>

        /// <returns></returns>

        public static int GetRandomInt()

        {

            return GetRandomInt(int.MaxValue);

        }