问题描述
在我的xamarin.forms应用程序中,我使用“相机”视图和自定义渲染创建了一个自定义相机。一切正常。在拍摄照片后的android中,我可以检查所拍摄的照片是否包含人脸。这可以通过使用Camera.IFaceDetectionListener
完成。我的问题是如何在iOS中实现这一目标?我知道有视觉API。但是我不希望有实时面部跟踪。我只是想检查拍摄的照片是否包含脸部。任何帮助表示赞赏。
我的iOS CameraPreview
public class UICameraPreview : UIView,IAVCaptureMetadataOutputObjectsDelegate
{
AVCaptureVideoPreviewLayer previewLayer;
public AVCaptureDevice[] videoDevices;
CameraOptions cameraOptions;
public AVCaptureStillImageOutput stillImageOutput;
public AVCaptureDeviceInput captureDeviceInput;
public AVCaptureDevice device;
public event EventHandler<EventArgs> Tapped;
public AVCaptureSession CaptureSession { get; set; }
public bool IsPreviewing { get; set; }
public AVCaptureStillImageOutput CaptureOutput { get; set; }
public UICameraPreview(CameraOptions options)
{
cameraOptions = options;
IsPreviewing = false;
Initialize();
}
public override void LayoutSubviews()
{
base.LayoutSubviews();
if (previewLayer != null)
previewLayer.Frame = Bounds;
}
public override void touchesBegan(NSSet touches,UIEvent evt)
{
base.touchesBegan(touches,evt);
OnTapped();
}
protected virtual void OnTapped()
{
var eventHandler = Tapped;
if (eventHandler != null)
{
eventHandler(this,new EventArgs());
}
}
void Initialize()
{
CaptureSession = new AVCaptureSession();
previewLayer = new AVCaptureVideoPreviewLayer(CaptureSession)
{
Frame = Bounds,VideoGravity = AVLayerVideoGravity.ResizeAspectFill
};
videoDevices = AVCaptureDevice.DevicesWithMediaType(AVMediaType.Video);
var cameraPosition = (cameraOptions == CameraOptions.Front) ? AVCaptureDevicePosition.Front : AVCaptureDevicePosition.Back;
device = videoDevices.FirstOrDefault(d => d.Position == cameraPosition);
if (device == null)
{
return;
}
NSError error;
captureDeviceInput = new AVCaptureDeviceInput(device,out error);
CaptureSession.AddInput(captureDeviceInput);
var dictionary = new NSMutableDictionary();
dictionary[AVVideo.CodecKey] = new NSNumber((int)AVVideoCodec.JPEG);
stillImageOutput = new AVCaptureStillImageOutput()
{
OutputSettings = new NSDictionary()
};
CaptureSession.AddOutput(stillImageOutput);
Layer.AddSublayer(previewLayer);
CaptureSession.StartRunning();
IsPreviewing = true;
}
// Photo Capturing
public async Task CapturePhoto()
{
try
{
var videoConnection = stillImageOutput.ConnectionFromMediaType(AVMediaType.Video);
var sampleBuffer = await stillImageOutput.CaptureStillImageTaskAsync(videoConnection);
var jpegData = AVCaptureStillImageOutput.JpegStillToNSData(sampleBuffer);
var photo = new UIImage(jpegData);
var rotatedPhoto = RotateImage(photo,180f);
var img = rotatedPhoto;
CALayer layer = new CALayer
{
ContentsScale = 1.0f,Frame = Bounds,Contents = rotatedPhoto.CGImage //Contents = photo.CGImage,};
CaptureSession.StopRunning();
photo.SavetoPhotosAlbum((image,error) =>
{
if (!string.IsNullOrEmpty(error?.LocalizedDescription))
{
Console.Error.WriteLine($"\t\t\tError: {error.LocalizedDescription}");
}
});
}
catch (Exception ex)
{
}
//MainPage.UpdateSource(UIImageFromLayer(layer).AsJPEG().Asstream());
//MainPage.UpdateImage(UIImageFromLayer(layer).AsJPEG().Asstream());
}
}
我的CameraPrevieWrenderer
public class CameraPrevieWrenderer : VieWrenderer<CameraPreview,UICameraPreview>,IAVCaptureMetadataOutputObjectsDelegate
{
UICameraPreview uiCameraPreview;
AVCaptureSession captureSession;
AVCaptureDeviceInput captureDeviceInput;
AVCaptureStillImageOutput stillImageOutput;
protected override void OnElementChanged(ElementChangedEventArgs<CameraPreview> e)
{
base.OnElementChanged(e);
if (e.OldElement != null)
{
// Unsubscribe
uiCameraPreview.Tapped -= OnCameraPreviewTapped;
}
if (e.NewElement != null)
{
if (Control == null)
{
uiCameraPreview = new UICameraPreview(e.NewElement.Camera);
SetNativeControl(uiCameraPreview);
MessagingCenter.Subscribe<Camera_Popup>(this,"CaptureClick",async (sender) =>
{
try
{
// Using messeging center to take photo when clicking button from shared code
var data = new AVCaptureMetadataOutputObjectsDelegate();
await uiCameraPreview.CapturePhoto();
}
catch (Exception ex)
{
return;
}
});
}
MessagingCenter.Subscribe<Camera_Popup>(this,"RetryClick",(sender) =>
{
Device.BeginInvokeOnMainThread(() =>
{
uiCameraPreview.CaptureSession.StartRunning();
uiCameraPreview.IsPreviewing = true;
});
});
MessagingCenter.Subscribe<Camera_Popup>(this,"FlipClick",(sender) =>
{
try
{
var devicePosition = uiCameraPreview.captureDeviceInput.Device.Position;
if (devicePosition == AVCaptureDevicePosition.Front)
{
devicePosition = AVCaptureDevicePosition.Back;
}
else
{
devicePosition = AVCaptureDevicePosition.Front;
}
uiCameraPreview.device = uiCameraPreview.videoDevices.FirstOrDefault(d => d.Position == devicePosition);
uiCameraPreview.CaptureSession.BeginConfiguration();
uiCameraPreview.CaptureSession.RemoveInput(uiCameraPreview.captureDeviceInput);
uiCameraPreview.captureDeviceInput = AVCaptureDeviceInput.FromDevice(uiCameraPreview.device);
uiCameraPreview.CaptureSession.AddInput(uiCameraPreview.captureDeviceInput);
uiCameraPreview.CaptureSession.CommitConfiguration();
}
catch (Exception ex)
{
var abc = ex.InnerException.Message;
}
});
uiCameraPreview.Tapped += OnCameraPreviewTapped;
}
}
void OnCameraPreviewTapped(object sender,EventArgs e)
{
if (uiCameraPreview.IsPreviewing)
{
uiCameraPreview.CaptureSession.StopRunning();
uiCameraPreview.IsPreviewing = false;
}
else
{
uiCameraPreview.CaptureSession.StartRunning();
uiCameraPreview.IsPreviewing = true;
}
}
protected override void dispose(bool disposing)
{
if (disposing)
{
Control.CaptureSession.dispose();
Control.dispose();
}
base.dispose(disposing);
}
}
解决方法
CoreImage
框架具有CIDetector
,该框架提供了用于面部,QR码,文本...的图像检测器,您可以在其中传递图像并获得特定的“功能集”。
Xamarin文档中的示例:
var imageFile = "photoFace2.jpg";
var image = new UIImage(imageFile);
var context = new CIContext ();
var detector = CIDetector.CreateFaceDetector (context,true);
var ciImage = CIImage.FromCGImage (image.CGImage);
var features = detector.GetFeatures (ciImage);
Console.WriteLine ("Found " + features.Length + " faces");
re:https://docs.microsoft.com/en-us/dotnet/api/CoreImage.CIDetector?view=xamarin-ios-sdk-12