用于保存CameraCaptureSequence中的图像数据的MemoryStream为0，即使CameraCaptureSequence中存在图像数据

Question

我正在使用PhotoCaptureDevice类，我可以捕获相机帧，但是当我将CameraCaptureSequence的CameraCaptureFrame.CaptureSequence中的图像数据复制到MemoryStream中时出现错误，然后将其保存在相机胶卷中。这是我正在尝试做的代码片段。

PhotoCaptureDevice cam;    
cam = await PhotoCaptureDevice.OpenAsync(<front/rear depending on user input>,<resolution depends on user input>);

CameraCaptureSequence seq;
seq = cam.CreateCaptureSequence(1);

cam.SetProperty(KnownCameraGeneralProperties.PlayShutterSoundOnCapture, true);

MemoryStream captureStream1 = new MemoryStream();
seq.Frames[0].CaptureStream = captureStream1.AsOutputStream();//This stream is for saving the image data to camera roll

await cam.PrepareCaptureSequenceAsync(seq);
await seq.StartCaptureAsync();

bool a = seq.Frames[0].CaptureStream.Equals(0);//This value is false during debugging
if(capturestream1.Length>0)//This condition evaluates to false
{
MediaLibrary library = new MediaLibrary();
Picture picture1 = library.SavePictureToCameraRoll("image1", captureStream1);
}
else
{
//Logic to handle condition
}

正如我在评论中添加的那样，变量bool a的计算结果为false，我通过调试代码来检查。但由于某种原因，capturestream1.Length属性为0。

Answer 1

以下是有关如何使用单个图像捕获序列并将该图像保存到MediaLibrary的代码段。显然这对于​​这个API来说是一个微不足道的例子，因为序列非常适合捕获多个图像并将它们与后处理一起进行网格化。

private async void MainPage_Loaded(object sender, RoutedEventArgs e)
{
    using (MemoryStream stream = new MemoryStream())
    using (var camera = await PhotoCaptureDevice.OpenAsync(CameraSensorLocation.Back,
            PhotoCaptureDevice.GetAvailableCaptureResolutions(CameraSensorLocation.Back).First()))
    {
        var sequence = camera.CreateCaptureSequence(1);
        sequence.Frames[0].CaptureStream = stream.AsOutputStream();
        camera.PrepareCaptureSequenceAsync(sequence);
        await sequence.StartCaptureAsync();

        stream.Seek(0, SeekOrigin.Begin);

        using (var library = new MediaLibrary())
        {
            library.SavePictureToCameraRoll("currentImage.jpg", stream);
        }
    }
}

运行此代码段时，您可以看到存储在设备上的图像：

您可以在诺基亚的Camera Explorer应用程序中找到完整的工作样本，该应用程序演示WP8相机API的端到端用例：http://projects.developer.nokia.com/cameraexplorer