从WinRT Camera Capture UI检索文件内容

Question

我正在尝试从Camera Capture UI中获取压缩的JPEG数据,但我在IInputBuffer附近绊倒了.这是我得到的:

private async void OnWebcamButton(object sender, RoutedEventArgs e)
{
    var captureUi = new CameraCaptureUI();
    var result = await captureUi.CaptureFileAsync(CameraCaptureUIMode.Photo);
    var file = await result.OpenForReadAsync();
    var reader = new DataReader(file);

    byte[] data = new byte[reader.UnconsumedBufferLength];
    await reader.LoadAsync(reader.UnconsumedBufferLength);
    reader.ReadBytes(data);

    // XXX: This is always zero
    Debug.Text = String.Format("Buffer is {0} bytes", data.Length);
}

我有什么想法我做错了吗？

Answer 1

我觉得你根本不需要DataReader这里.试试这个:

using System.Runtime.InteropServices.WindowsRuntime; // for AsBuffer()
...
var file = await captureUi.CaptureFileAsync(CameraCaptureUIMode.Photo);
var stream = await result.OpenForReadAsync();
byte[] data = new byte[file.Size];
await stream.ReadAsync(data.AsBuffer(), (uint)data.Length, InputStreamOptions.None);

或者,您可以使用AsStream()扩展方法(from System.IO.WindowsRuntimeStreamExtensons)将WinRT包装IInputStream为System.IO.Stream,然后使用常规.NET技术.