C＃UWP從System.IO.Stream轉換為Windows.Storage.Streams.IRandomAccessStreamWithContentType

Question

所以我試圖獲得IRandomAccessStreamWithContentType但不能，因為我得到異常：

"This IRandomAccessStream does not support the CloneStream method because it requires cloning and this stream does not support cloning."

這發生在以下代碼的最后一行：

PixelDataProvider pix = await decoder.GetPixelDataAsync(
                BitmapPixelFormat.Bgra8,
                BitmapAlphaMode.Straight,
                transform,
                ExifOrientationMode.IgnoreExifOrientation,
                ColorManagementMode.ColorManageToSRgb);
byte[] pixels = pix.DetachPixelData();

Stream pixStream = cropBmp.PixelBuffer.AsStream();
pixStream.Write(pixels, 0, (int)(width * height * 4));
IRandomAccessStream iStream= pixStream.AsRandomAccessStream(); //dafaq with streams
RandomAccessStreamReference iReferenceStream= RandomAccessStreamReference.CreateFromStream(iStream);
IRandomAccessStreamWithContentType newStream = await iReferenceStream.OpenReadAsync();

有沒有解決方法或什么？

編輯1

我也試過這種方式，仍然無法正常工作。 （但現在我得到null而不是克隆失敗了）

InMemoryRandomAccessStream ras = new InMemoryRandomAccessStream();
await ras.WriteAsync(pixels.AsBuffer());
RandomAccessStreamReference iReferenceStream = RandomAccessStreamReference.CreateFromStream(ras);
IRandomAccessStreamWithContentType newStream = await iReferenceStream.OpenReadAsync();

Answer 1

從您的代碼中，您似乎使用了BitmapDecoder 。 BitmapDecoder提供對位圖容器數據的讀訪問以及來自第一幀的數據。

我們應該能夠為編碼器創建一個新的InMemoryRandomAccessStream來寫入並調用BitmapEncoder.CreateForTranscodingAsync ，傳入內存中的流和解碼器對象。

例如：

Windows.Storage.Streams.IRandomAccessStream random = await Windows.Storage.Streams.RandomAccessStreamReference.CreateFromUri(new Uri("ms-appx:///Assets/sunset.jpg")).OpenReadAsync();
Windows.Graphics.Imaging.BitmapDecoder decoder = await Windows.Graphics.Imaging.BitmapDecoder.CreateAsync(random);
Windows.Graphics.Imaging.PixelDataProvider pixelData = await decoder.GetPixelDataAsync();
byte[] buffer = pixelData.DetachPixelData();
InMemoryRandomAccessStream inMemoryRandomAccessStream = new InMemoryRandomAccessStream();
BitmapEncoder encoder = await BitmapEncoder.CreateForTranscodingAsync(inMemoryRandomAccessStream, decoder);
encoder.BitmapTransform.ScaledWidth = 320;
encoder.BitmapTransform.ScaledHeight = 240;
await encoder.FlushAsync();
inMemoryRandomAccessStream.Seek(0);
random.Seek(0);
BitmapImage bitmapImage = new BitmapImage();
RandomAccessStreamReference iReferenceStream = RandomAccessStreamReference.CreateFromStream(inMemoryRandomAccessStream);
IRandomAccessStreamWithContentType newStream = await iReferenceStream.OpenReadAsync();
bitmapImage.SetSource(newStream);
MyImage.Source = bitmapImage;