Clash Royale CLAN TAG#URR8PPP

MemoryStream to BitmapImage

I am having a bit of a hard time converting MemoryStream into BitmapImage. There are a lot of questions on SO regarding similar situations, but after trying everything on them, I've been unable to fix this, so I turn to you. Note that I'm working with Magick.NET (ImageMagick.NET) and Tessnet2 -- that is what some of that code is.

MemoryStream

BitmapImage

SO

Magick.NET

Tessnet2

I use Bitmap class to do most of the work in Magick.NET and Tessnet2. BitmapImage is used for displaying purposes.

Bitmap

BitmapImage

First, I load up the PDF and extract a cropped bitmap from its first page:

public Task PdfToBmp(string path)

return Task.Run(() =>

using (var image = new MagickImage())

MagickNET.SetGhostscriptDirectory("./");

var settings = new MagickReadSettings

Density = new MagickGeometry(300, 300),
FrameCount = 1
;

image.Read(path, settings);
image.Crop(new MagickGeometry(1850, 200, 600, 140));

// ImageStream is a MemoryStream property.
ImageStream = new MemoryStream();
image.Write(ImageStream, MagickFormat.Bmp);
ImageStream.Position = 0;

);



That is when I save the bitmap into the MemoryStream. Once I have MemoryStream loaded up, I move onto working with it. I instantiate a Bitmap, so that I may use it for Tessnet2 related work and then try to instantiate a BitmapImage.

MemoryStream

MemoryStream

Bitmap

Tessnet2

BitmapImage

public Task DoOcr()

if (ImageStream == null)

return null;


TargetImage = new Bitmap(ImageStream);
ImageStream.Position = 0;

// ----------------------- Problem Area ----------------------- //
DisplayImage = new BitmapImage();
DisplayImage.BeginInit();
DisplayImage.StreamSource = ImageStream;
DisplayImage.CacheOption = BitmapCacheOption.OnLoad;
DisplayImage.EndInit();

//ImageStream.Close();
// ------------------------------------------------------------ //

return Task.Run(() =>

var ocr = new Tesseract();
ocr.Init("tessdata", "eng", false);
var results = ocr.DoOCR(TargetImage, Rectangle.Empty);
Dispatcher.Invoke(() =>

Results = new ObservableCollection<Word>(results);
);
);



This is where I'm having a problem. Without that DisplayImage block, the program runs fine and I just don't get the displayed image. I'm even able to save the Bitmap (TargetImage) to a file with no problems. However, with the DisplayImage block, I get System.NullReferenceException:

DisplayImage

Bitmap

TargetImage

DisplayImage

System.NullReferenceException

System.NullReferenceException occurred
_HResult=-2147467261
_message=Object reference not set to an instance of an object.
HResult=-2147467261
IsTransient=false
Message=Object reference not set to an instance of an object.
Source=System
StackTrace:
at System.Uri.CreateThisFromUri(Uri otherUri)
InnerException:


I'm unable to pinpoint where it occurs exactly, because the ImageStream object looks "fine" upon inspection. It contains data and is at position 0. If I try to close it, or do anything with it, after assigning it as the StreamSource to DisplayImage, I get a null exception on the line that attempts to perform such action. I even tried creating two different streams, to see if that's the problem; however, I was getting the exact same behavior. Debugging this is kind of a pain, considering it doesn't point to any one specific line. There's obviously an issue between this MemoryStream and BitmapImage. Could it be possible that there's some sort of format/conversion problem between the two, but not between MemoryStream and Bitmap in this particular situation?

ImageStream

StreamSource

DisplayImage

null

MemoryStream

BitmapImage

MemoryStream

Bitmap

I tried the file route, where I save MagickImage to a file and load it up into BitmapImage through Uri and it worked flawlessly; however, I would like to be able to perform this in-memory. By the way, setting position to 0 on the MemoryStream did not seem to affect either Bitmap (loads properly) or BitmapImage (same exception).

MagickImage

BitmapImage

Uri

0

Bitmap

BitmapImage

The temporary fix I currently use is to make DisplayImage a BitmapSource, rather than BitmapImage:

DisplayImage

BitmapSource

BitmapImage

DisplayImage = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(
TargetImage.GetHbitmap(), IntPtr.Zero, Int32Rect.Empty,
BitmapSizeOptions.FromWidthAndHeight(TargetImage.Width, TargetImage.Height));


Bitmap

BitmapImage

1 Answer
1

The Magick.NET's Write() method has some bugs, so we have to use ToBitmap().

Write()

ToBitmap()

image.ToBitmap().Save(ImageStream, System.Drawing.Imaging.ImageFormat.Bmp);


By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.