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搜尋 jpeg 結果:
.Net 6 的 Captcha 實做
產生 FileStreamResult 物件的 function 如下: (目前置於 SU 之中,以便轉移)

        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" };
        }



輸出用的 Controller 和 Action 如下:

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);
        }
    }
}
More...
Bike, 2022/9/25 下午 10:03:44
.Net Framework 的檔案檢查機制 Web API 和 MVC 5
我們的目標是在啟動時,掛一個 global filter 來檢查上傳的檔案附檔名,避免上傳未預期的可執行檔。使用 global filter 可以防止程式設計師忘了做檔案檢查,發生危險。我們目前用到的 .Net Framework 有兩個類別,一個是 System.Web.Http.ApiController,另一個是 System.Web.Mvc.Controller,兩個要分開處理。

1. Web API (System.Web.Http.ApiController)
.Net Framework 的 Web API 2 在接收檔案時,必需使用 Request.Content.ReadAsMultipartAsync 把上傳的資料存入 MultipartMemoryStreamProvider 之後再來處理。
範例如下: 
    public class UploadController : ApiController
    {
        public async Task<object> PostFormData()
        {
            var provider = new MultipartMemoryStreamProvider();

            if (! Request.Content.IsMimeMultipartContent())
            {
                return "no file";
            }

            //要注意這裡的 await
            await Request.Content.ReadAsMultipartAsync(provider);

            foreach (var content in provider.Contents)
            {
                if (content.Headers.ContentDisposition.FileName != null)
                {
                    string localFilename = content.Headers.ContentDisposition.FileName.Replace("\"", "");
                    System.IO.Directory.CreateDirectory(HttpContext.Current.Server.MapPath(@"~/App_Data/Temp/"));
                    string filename = HttpContext.Current.Server.MapPath(@"~/App_Data/Temp/" + localFilename);
                    if (System.IO.File.Exists(filename))
                    {
                        System.IO.File.Delete(filename);
                    }

                    using (var fileStream = new FileStream(filename, FileMode.Create, FileAccess.Write))
                    {
                        var contentStream = await content.ReadAsStreamAsync();
                        await contentStream.CopyToAsync(fileStream);
                        Trace.WriteLine("Save To" + filename);
                    }
                }
            }
            return "OK";
        }
    }


程式碼中有個地方我沒有注意到。我一開始是用 Request.Content.ReadAsMultipartAsync(provider); 把資料讀進 provider,但前方沒有加上 await,造成有時讀不到檔案的情況,再次提醒自己 Async 和 Await 的關係。

直覺的想法是在 filter 中執行一樣的程式碼,不存檔,只要抓出檔名來檢查即可。但這時遇到一個問題 Request.Content.ReadAsMultipartAsync 不能執行兩次,Google 了一陣子,也沒找不到類似 seek(0) 的操作。所以只好自己寫一個暫存的機製。

這裡決定使用 System.Web.HttpContext.Current.Items 來暫存 provider,最後的 OnActionExecutingAsync 結果如下:

        /// <summary>
        /// 檔案檢查
        /// </summary>
        /// <param name="actionContext"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public override async Task OnActionExecutingAsync(HttpActionContext actionContext, CancellationToken cancellationToken)
        {
            Trace.WriteLine("ApiCheckFile OnActionExecutingAsync");

            var request = actionContext.Request;
            if (!request.Content.IsMimeMultipartContent())
            {
                return;
            }

            var provider = new MultipartMemoryStreamProvider();
            await request.Content.ReadAsMultipartAsync(provider);

            //把 provider 存入 System.Web.HttpContext.Current.Items 之中,以便在 controller 中再度使用
            System.Web.HttpContext.Current.Items["MimeMultipartContentProvider"] = provider;

            foreach (var content in provider.Contents)
            {
                if (content.Headers.ContentDisposition.FileName != null)
                {
                    var filename = content.Headers.ContentDisposition.FileName.Replace("\"", "");
                    Trace.WriteLine(filename);

                    var ext = System.IO.Path.GetExtension(filename);
                    if (!".jpg,.jpeg,.png".Contains(ext.ToLower()))
                    {
                        throw new Exception("file format error.");
                    }
                }
            }

            return;
        }


而 controller 中的 Action 則改為以下的版本;本版本中,除了把上傳的檔案存檔以外,還有讀取 form data 中其它欄位的範例:

        public async Task<object> PostFormData()
        {
            //改由 HttpContext.Current.Items 中,讀取資料。
            MultipartMemoryStreamProvider provider = (MultipartMemoryStreamProvider)System.Web.HttpContext.Current.Items["MimeMultipartContentProvider"];

            //如果沒有經過 filter,provider會是 null, 這時就要直接由 Request.Content 讀入 provider
            if (provider == null)
            {
                provider = new MultipartMemoryStreamProvider();
                Request.Content.ReadAsMultipartAsync(provider);
            }

            foreach (var content in provider.Contents)
            {
                if (content.Headers.ContentDisposition.FileName != null)
                {
                    string localFilename = content.Headers.ContentDisposition.FileName.Replace("\"", "");
                    Trace.WriteLine("FileName: " + localFilename);
                    Trace.WriteLine("FileName: " + @"~/App_Data/Temp/" + localFilename);
                    System.IO.Directory.CreateDirectory(HttpContext.Current.Server.MapPath(@"~/App_Data/Temp/"));
                    string filename = HttpContext.Current.Server.MapPath(@"~/App_Data/Temp/" + localFilename);
                    if (System.IO.File.Exists(filename))
                    {
                        System.IO.File.Delete(filename);
                    }

                    using (var fileStream = new FileStream(filename, FileMode.Create, FileAccess.Write))
                    {
                        var contentStream = await content.ReadAsStreamAsync();
                        await contentStream.CopyToAsync(fileStream);
                        Trace.WriteLine("Save To" + filename);
                    }
                }
                else
                {
                    var contentStream = await content.ReadAsStreamAsync();
                    var reader = new System.IO.StreamReader(contentStream);
                    var data = reader.ReadToEnd();
                    Trace.WriteLine("data: " + data);
                }
            }
            return "OK";
        }


以上是展示 Web Api 的 Filter。

如果是 MVC 的 Controller,就簡單多了,直接讀取 actionContext.HttpContext.Request.Files 裡面各檔案的 FileName 即可。不過也遇到了一個和直覺不同的地方,對 actionContext.HttpContext.Request.Files 居然不能用 foreach 請見下方註解掉的地方。也許是我的用法有問題,如果有人找到可以使用的方法也麻煩告知。

        public override void OnActionExecuting(ActionExecutingContext actionContext)
        {
            Debug.WriteLine("MvcCheckFileFilter OnActionExecuting");
            if (actionContext.HttpContext.Request.Files.Count > 0)
            {
                for (int i = 0; i < actionContext.HttpContext.Request.Files.Count; i++)
                {
                    System.Web.HttpPostedFileBase file = actionContext.HttpContext.Request.Files[i];
                    if (System.IO.Path.GetExtension(file.FileName) != ".jpg")
                    {
                        throw new Exception("file format error.");
                    }
                    Debug.WriteLine(i + "MvcCheckFileFilter OnActionExecuting File type: " + file.FileName.ToString());
                }
            }

            //以下寫法會發生錯誤: 無法將類型 'System.String' 的物件轉換為類型 'System.Web.HttpPostedFileBase'。
            //foreach (HttpPostedFileBase file in actionContext.HttpContext.Request.Files)
            //{
            //    if (System.IO.Path.GetExtension(file.FileName) != ".jpg")
            //    {
            //        throw new Exception("file format error.");
            //    }
            //}
        }


最後是把 filter 掛在 global filter 裡,如下:
Web API Controller 的部份:
在 WebApiConfig.cs 裡加上 config.Filters.Add(new ApiCheckFile()); 見下圖:
 

附帶一提,Register 是在 global.asax 裡被叫用的。微軟的架構常常這樣,硬是拉到另一個目錄的獨立檔案裡,如果 global.asax 沒有這一行,不知所以的人,在 App_Start 裡,建立了一個 WebApiConfig.cs 然後會發現完全沒做用... 見下圖

 
MVC Controller 的部份,
在 FilterConfig.cs 中,加上 filters.Add(new MvcCheckFileFilter()); 如下圖
 

一樣是在 global.asax 中呼叫  FilterConfig.RegisterGlobalFilters,見下圖:

 
不過有趣的地方是,在 global.asax 裡, WebApiConfig.Register 和 FilterConfig.RegisterGlobalFilters 的叫用方法不同,一個是把 function 當作變數,一個是直接呼叫 function, 大家可以比較一下。

附註 1, 關於 OnActionExecutingAsync 和 OnActionExecuting:

Web API 的 filter 中,提供了 OnActionExecutingAsync 和 OnActionExecuting 兩個 method 可以 override ,我實驗的結果是如果兩個 method 都 override 了,只有 OnActionExecutingAsync 會被呼叫。

MVC 的 filter 中,只有 OnActionExecuting 可以 override。
 
More...
Bike, 2022/5/15 上午 10:01:11
簡單的 HTTP Relay By MVC.
客戶要求
1. 檔案只能放在 Firewall 內的後台用 Web server (Server A).
2. 使用者只能存取 DMZ 的 Web server (Server B).
3. Server B 只能用 HTTP 通過 Firewall 向 Server A 要資料.(i.e.  Server B 不能掛戴 Server A 的目錄成為虛擬目錄)

所以在 Server B 上面建立了一支程式用 HTTP 的方式讀取 Server A 的檔案再寫出去.

例如, http://ServerB/Upload/test.pdf 會讀取 http://ServerA/Upload/test.pdf 再送到 Client 端

namespace WWW.Controllers
{
    public class UploadController : Controller
    {
        // GET: Upload
        public void Index(string Filename)
        {
            //Create a stream for the file
            Stream stream = null;

            //This controls how many bytes to read at a time and send to the client
            int bytesToRead = 10000;

            // Buffer to read bytes in chunk size specified above
            byte[] buffer = new Byte[bytesToRead];

            string url = "http://admin-dev.nanya.bike.idv.tw/newnanyaback/Upload/" + Filename;

            // The number of bytes read
            try
            {
                //Create a WebRequest to get the file
                HttpWebRequest fileReq = (HttpWebRequest)HttpWebRequest.Create(url);

                //Create a response for this request
                HttpWebResponse fileResp = (HttpWebResponse)fileReq.GetResponse();

                if (fileReq.ContentLength > 0)
                    fileResp.ContentLength = fileReq.ContentLength;

                //Get the Stream returned from the response
                stream = fileResp.GetResponseStream();

                // prepare the response to the client. resp is the client Response
                var resp = HttpContext.Response;

                if (Filename.ToLower().EndsWith(".png") ||
                    Filename.ToLower().EndsWith(".jpg") ||
                    Filename.ToLower().EndsWith(".jpeg") ||
                    Filename.ToLower().EndsWith(".gif")
                    )
                {
                    resp.ContentType = "image";
                }
                else
                {
                    //Indicate the type of data being sent
                    resp.ContentType = "application/octet-stream";

                    //Name the file
                    resp.AddHeader("Content-Disposition", "attachment; filename=\"" + HttpUtility.UrlEncode(Filename, Encoding.UTF8) + "\"");
                }

                resp.AddHeader("Content-Length", fileResp.ContentLength.ToString());

                int length;
                do
                {
                    // Verify that the client is connected.
                    if (resp.IsClientConnected)
                    {
                        // Read data into the buffer.
                        length = stream.Read(buffer, 0, bytesToRead);

                        // and write it out to the response's output stream
                        resp.OutputStream.Write(buffer, 0, length);

                        // Flush the data
                        resp.Flush();

                        //Clear the buffer
                        buffer = new Byte[bytesToRead];
                    }
                    else
                    {
                        // cancel the download if client has disconnected
                        length = -1;
                    }
                } while (length > 0); //Repeat until no data is read
            }
            finally
            {
                if (stream != null)
                {
                    //Close the input stream
                    stream.Close();
                }
            }
        }
    }
}



但不是這樣就好了, 在 RouteConfig.cs 中要加上:
            routes.MapRoute(
                name: "Upload",
                url: "Upload/{filename}",
                defaults: new { controller = "Upload", action = "Index", filename = UrlParameter.Optional }
            );

此外在 Web.Config 中也要加上:

  <system.webServer>
    <handlers>
      <add name="UrlRoutingHandler_Upload"
           type="System.Web.Routing.UrlRoutingHandler, 
               System.Web, Version=4.0.0.0, 
               Culture=neutral, 
               PublicKeyToken=b03f5f7f11d50a3a"
           path="/Upload/*"
           verb="GET"/>
    </handlers>
  </system.webServer>

參考:
http://stackoverflow.com/questions/5596747/download-stream-file-from-url-asp-net

http://blog.darkthread.net/post-2014-12-05-mvc-routing-for-url-with-filename.aspx
More...
Bike, 2016/12/1 下午 09:34:30
上傳的圖片在顯示時被轉 90 度
這通常是手機或相機拍照時有旋轉造成的.

參考: http://automagical.rationalmind.net/2009/08/25/correct-photo-orientation-using-exif/

程式碼:

    void RotatePic(string pathToImageFile)
    {
        // Rotate the image according to EXIF data
        var bmp = new Bitmap(pathToImageFile);
        var exif = new EXIFextractor(ref bmp, "n"); // get source from http://www.codeproject.com/KB/graphics/exifextractor.aspx?fid=207371

        if (exif["Orientation"] != null)
        {
            RotateFlipType flip = OrientationToFlipType(exif["Orientation"].ToString());

            if (flip != RotateFlipType.RotateNoneFlipNone) // don't flip of orientation is correct
            {
                bmp.RotateFlip(flip);
                exif.setTag(0x112, "1"); // Optional: reset orientation tag
                bmp.Save(pathToImageFile, ImageFormat.Jpeg);
            }
        }

        bmp.Dispose();
    }

    private static RotateFlipType OrientationToFlipType(string orientation)
    {
        switch (int.Parse(orientation))
        {
            case 1:
                return RotateFlipType.RotateNoneFlipNone;
                break;
            case 2:
                return RotateFlipType.RotateNoneFlipX;
                break;
            case 3:
                return RotateFlipType.Rotate180FlipNone;
                break;
            case 4:
                return RotateFlipType.Rotate180FlipX;
                break;
            case 5:
                return RotateFlipType.Rotate90FlipX;
                break;
            case 6:
                return RotateFlipType.Rotate90FlipNone;
                break;
            case 7:
                return RotateFlipType.Rotate270FlipX;
                break;
            case 8:
                return RotateFlipType.Rotate270FlipNone;
                break;
            default:
                return RotateFlipType.RotateNoneFlipNone;
        }
    }
More...
Bike, 2016/12/1 下午 09:15:00
facebook 網頁分享 Debug 模式
當我們網站裡的某個網址要分享到 facebook 時,
facebook 會主動到我們網頁擷取內容,然後存在cache裡
facebook 給開發人員一個頁面可以測試看看結果
https://developers.facebook.com/tools/debug/og/object/ 
可以貼上自己網站的某個網址 ex.
http://www.shopunt.com/eng/unreal-touch-mineral-powder-blush/p/1129/c/34
就可以看到 facebook 爬到的結果,如果上次爬的是很久以前,這個地方也可以重新爬一次

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經由測試結果,發現這功能出現的圖片,跟實際上在網站裡點fb分享出現的內容還是有差異
想出現的圖片還是不能控制,根據[此文章]說明
要把 og: 所有屬性都加上才行
header 圖片部分最好再加上
<link href="圖片連結網址" rel="image_src" type="image/jpeg">

應該就能保證分享圖片是自己想要的。 --> 這有空再來測試好了
 
More...
darren, 2014/8/13 下午 07:32:59
ASPJPEG on 64bit IIS
啟用 32 位元應用程式要設為 False。

More...
Bike, 2013/10/3 下午 02:44:25
~ Uwinfo ~