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Normal Topic Image is blank when trying to download the diagram image file (Read 210 times)
Megan1717
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Image is blank when trying to download the diagram image file
Aug 31st, 2021 at 10:22pm
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Hello,

We would like to allow users to download the diagram as a PNG image. However, currently the downloaded image file is empty (zero KB) and there is a message on the file saying "this file format is not supported".

Here is the controller code we are using:

Code (Java)
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 public ActionResult DownloadDiagramImage(string diagramJson)
        {
                DiagramView view = DiagramView.FromJson(diagramJson);
                Image diagramImage = view.Diagram.CreateImage();
                MemoryStream memoryStream = new MemoryStream();
                diagramImage.Save(memoryStream, ImageFormat.Png);
                return File(memoryStream, "image/png", "diagram.png"));
        }
 



While there is a way to download it after first saving the file to the server, we would prefer to not have to read and write to a server folder in order to have a downloadable file. It seems that building it dynamically using the memory stream should work as we do this with dynamically created PDFs and Powerpoints using memory stream.

If you have any suggestions on how to build the diagram image dynamically and return the file from the controller method so that it can be downloaded client-side, that would be very much appreciated.

Thanks.
  
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Slavcho
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Re: Image is blank when trying to download the diagram image file
Reply #1 - Sep 1st, 2021 at 1:20pm
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Hi,

You'll need to reset stream's position to 0 before passing it to the File response:

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diagramImage.Save(memoryStream, ImageFormat.Png);
memoryStream.Position = 0;
return File(memoryStream, "image/png", "diagram.png"); 



or pass the stream bytes to File instead:

Code
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return File(memoryStream.ToArray(), "image/png", "diagram.png");  



Regards,
Slavcho
Mindfusion
  
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Megan1717
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Re: Image is blank when trying to download the diagram image file
Reply #2 - Sep 2nd, 2021 at 11:47pm
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That worked. Thanks very much!
  
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