通過web api發送圖像返回

Question

我有一個奇怪的問題，通過web api返回圖像，我在我的應用程序中的幾個地方做了這個，但沒有失敗，但這一個正在導致我的問題，任何幫助將大大讚賞。

這工作

Bitmap bitmap = getImage(); 
     MemoryStream bitmapStream = new MemoryStream(); 
     bitmap.Save("C:\\test.png", System.Drawing.Imaging.ImageFormat.Png); 

     if (bitmap != null) 
     { 
      if (Request.Headers.IfModifiedSince.HasValue) 
      { 
       // The file has not been modified since the browser cached it. 
       return new HttpResponseMessage(HttpStatusCode.NotModified); 
      } 
      HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK); 
      response.Content = new StreamContent(new FileStream("C:\\test.png", FileMode.Open)); 
      response.Content.Headers.ContentType = new MediaTypeHeaderValue("image/png"); 
      return response; 
     } 
     else 
     { 
      return new HttpResponseMessage(HttpStatusCode.NotFound); 
     } 

雖然這並不

Bitmap bitmap = getImage(); 
     MemoryStream bitmapStream = new MemoryStream(); 
     bitmap.Save(bitmapStream, System.Drawing.Imaging.ImageFormat.Png); 

     if (bitmap != null) 
     { 
      if (Request.Headers.IfModifiedSince.HasValue) 
      { 
       // The file has not been modified since the browser cached it. 
       return new HttpResponseMessage(HttpStatusCode.NotModified); 
      } 
      HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK); 
      response.Content = new StreamContent(bitmapStream); 
      response.Content.Headers.ContentType = new MediaTypeHeaderValue("image/png"); 
      return response; 
     } 
     else 
     { 
      return new HttpResponseMessage(HttpStatusCode.NotFound); 
     } 

我真的需要做到這一點在內存中，而不是保存臨時文件來驅動，但由於某些原因，當我做到這一點的內存結果是一個空文件0字節，我嘗試手動設置內容長度，但然後該文件不下載。

Answer 1

保存發生後，您需要重置流的位置。

bitmapStream.Position = 0;