Question

我正在尝试在Windows 8桌面应用程序（WinForms .NET 4.5）中使用MediaCapture API。我可以使用API拍摄照片，但照片很暗。此外，MediaCapture API似乎不会自动触发相机闪光灯。

我尝试将亮度，合同，白平衡和曝光设置为自动每个MSDN文档。这是相关的代码。

     _mediaCapture = new MediaCapture();

     // init the settings of the capture
     var settings = new MediaCaptureInitializationSettings();
     settings.AudioDeviceId = "";
     settings.VideoDeviceId = _currentDeviceId;
     settings.PhotoCaptureSource = Windows.Media.Capture.PhotoCaptureSource.Photo;
     settings.StreamingCaptureMode = Windows.Media.Capture.StreamingCaptureMode.Video;
     await _mediaCapture.InitializeAsync(settings);

     // Find the highest resolution available
     ImageEncodingProperties resolutionMax = null;
     int max = 0;
     var resolutions = _mediaCapture.VideoDeviceController.GetAvailableMediaStreamProperties(MediaStreamType.Photo);
     foreach (IMediaEncodingProperties t in resolutions)
     {
        var properties = t as ImageEncodingProperties;
        if (properties != null)
        {
           var res = properties;
           if (res.Width * res.Height > max)
           {
              max = (int)(res.Width * res.Height);
              resolutionMax = res;
           }
        }
     }
     await _mediaCapture.VideoDeviceController.SetMediaStreamPropertiesAsync(MediaStreamType.Photo, resolutionMax);

     _mediaCapture.VideoDeviceController.Focus.TrySetAuto(true);

     _mediaCapture.VideoDeviceController.Brightness.TrySetAuto(true);

     _mediaCapture.VideoDeviceController.Contrast.TrySetAuto(true);

     _mediaCapture.VideoDeviceController.Exposure.TrySetAuto(true);

     _mediaCapture.VideoDeviceController.WhiteBalance.TrySetAuto(true);

     var imageProperties = ImageEncodingProperties.CreateJpeg();
     using (var fPhotoStream = new InMemoryRandomAccessStream())
     {
        // Take the photo and show it on the screen
        await _mediaCapture.CapturePhotoToStreamAsync(imageProperties, fPhotoStream);
        await fPhotoStream.FlushAsync();

        fPhotoStream.Seek(0);

        var bytes = new byte[fPhotoStream.Size];
        await fPhotoStream.ReadAsync(bytes.AsBuffer(), (uint)fPhotoStream.Size, InputStreamOptions.None);

        using (var byteStream = new MemoryStream(bytes))
        {
           return new Bitmap(byteStream);
        }
     }

非常感谢任何指导。

编辑：我将此代码移植到Metro应用程序，相机工作得很漂亮。我开始认为底层框架（Metro vs. Desktop）应该受到责备。

Answer 1

延迟回复，但如果将来有助于人们：黑暗图片通常是由于缺乏视频预览。相机驱动程序使用预览流来运行其3A算法（自动白平衡/聚焦/曝光）。目前让MediaCapture在桌面应用程序中预览有点挑战性。一种方法是创建一个D3DImage并依靠一些本地互操作来调用Media Foundation和DirectX。它不是微不足道的，但可以封装，因此C＃API表面仍然很简单。这是一些代码示例： https://github.com/mmaitre314/MediaCaptureWPF

Answer 2

您可以尝试按以下方式更改媒体设置，它应该更好：

settings.StreamingCaptureMode = Windows.Media.Capture.StreamingCaptureMode.AudioAndVideo;
settings.PhotoCaptureSource = Windows.Media.Capture.PhotoCaptureSource.VideoPreview;

Answer 3

await mc.InitializeAsync(new MediaCaptureInitializationSettings {
    PhotoCaptureSource = PhotoCaptureSource.VideoPreview }
);

是解决方案。

MediaCapture Windows 8桌面 - 照片很暗

3 个答案: