xamarin - 为什么使用 AVCaptureSession 时图像非常暗

Question

我们有 Xamarin Forms 解决方案，在 iOS 项目中，我们尝试在单击按钮时创建照片。问题是图像很暗。它几乎是黑色的。为什么会发生这种情况？这是一个代码:

var _captureSession = new AVCaptureSession();
var _captureDevice = AVCaptureDevice.GetDefaultDevice(AVMediaType.Video);
var _captureDeviceInput = AVCaptureDeviceInput.FromDevice(_captureDevice);
_captureSession.AddInput(_captureDeviceInput);
_captureSession.StartRunning();

private async void OnButtonClick()
{
    var output = new AVCaptureStillImageOutput { OutputSettings = new NSDictionary(AVVideo.CodecKey, AVVideo.CodecJPEG) };
    _captureSession.AddOutput(output);

    var buffer = await output.CaptureStillImageTaskAsync(output.Connections[0]);
    NSData data = AVCaptureStillImageOutput.JpegStillToNSData(buffer);

    UIImage image = UIImage.LoadFromData(data);
    //image = RotateImage(image);
    NSData imageData = image.AsPNG();
    byte[] byteArray = imageData.ToArray();

    IFolder folder = FileSystem.Current.LocalStorage;
    IFile file = await folder.CreateFileAsync("image.png", CreationCollisionOption.ReplaceExisting);

    using (Stream stream = await file.OpenAsync(PCLStorage.FileAccess.ReadAndWrite))
    {
        stream.Write(image, 0, image.Length);
    }
}

这是图片:

Answer 1

线路:

_captureSession.AddOutput(output);

应该在单击按钮之前(在开始运行之前)。更改后，图像具有正常亮度，并且不需要旋转。