WriteableBitmap's PixelWidth and PixelHeight propery does not change after a new SetSource

Question

I am not able to retrieve the width and the height of an image after I load it from a StorageFile object. Here is the code...

    FileOpenPicker^ openPicker = ref new FileOpenPicker();
    openPicker->ViewMode = PickerViewMode::Thumbnail;
    openPicker->SuggestedStartLocation = PickerLocationId::PicturesLibrary;
    openPicker->FileTypeFilter->Append(".jpg");
    openPicker->FileTypeFilter->Append(".jpeg");
    openPicker->FileTypeFilter->Append(".png");

	auto getStreamTask = create_task(openPicker->PickSingleFileAsync()).then([this](StorageFile^ file)
    {
        return file->OpenReadAsync();
    });
	
	getStreamTask.then(
    [this] (Windows::Storage::Streams::IRandomAccessStreamWithContentType^ stream)
    {
		WriteableBitmap^ bmp = ref new WriteabeBitmap(1, 1);
		bmp->SetSource(stream);
		displayImage->Source = bmp; // Displays correctly
		int Witdh = bmp->PixelWidth; // Remains 1
		int Height = bmp->PixelHeight; // Remains 1
    });

The PixelHeight and PixelWidth propery remains (1,1) for the bitmap. I tried displaying it in an image object in XAML and the image is displayed correctly though.

Answer 1

Hi,

 

Yes, writeableBitmap cannot calculate the height and width of that image, you can use BitmapImage class to get it.

 

		BitmapImage^ bmp=ref new BitmapImage();
		bmp->SetSource(stream);
		//bm->PixelHeight
		//WriteableBitmap^ bmp = ref new WriteabeBitmap(1, 1);
		//bmp->SetSource(stream);
		//displayImage->Source = bmp; // Displays correctly
		int Witdh = bmp->PixelWidth; // Remains 1
		int Height = bmp->PixelHeight; // Remains 1

Best regards,

Jesse

---

Jesse Jiang [MSFT]
MSDN Community Support | Feedback to us

Answer 2

Thanks Jesse!