Capture Image AVMetadataFaceObject with didOutputSampleBuffer: - uiimage

Question

I am trying to capture the face area.
Here is what I do , in didOutputMetadataObjects: is get the AVMetadataFaceObject and process it in didOutputSampleBuffer
didOutputMetadataObjects shows marker correctly, where I consider the Yaw, roll axis
What could be the best possible way, where I get only the face area and at the same time I see a face marker?
-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection
{
for(AVMetadataObject *metaObject in metadataObjects){
if([metaObject isKindOfClass:[AVMetadataFaceObject class ]] && metaObject.type == AVMetadataObjectTypeFace){
AVMetadataFaceObject * adjustedMeta = (AVMetadataFaceObject*)[self.videoLayer transformedMetadataObjectForMetadataObject:metaObject];
self.metaFaceObject= adjustedMeta;
//Draw the face marker here
}
}
}
AVCaptureVideoDataOutputSampleBufferDelegate
-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection{
CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
if(pixelBuffer ){
CFDictionaryRef attachments = CMCopyDictionaryOfAttachments( kCFAllocatorDefault, sampleBuffer, kCMAttachmentMode_ShouldPropagate );
CIImage *ciImage = [[CIImage alloc] initWithCVPixelBuffer:pixelBuffer options:(__bridge NSDictionary<NSString *,id> * _Nullable)(attachments)];
ciImage = [ciImage imageByCroppingToRect:self.metaFaceObject.bounds];
//This Image is upside down. Second thing the it does not have the face.
UIImage *image=[UIImage imageWithCIImage:ciImage];
}
}

Answer 1

hello some suggests below:
1: add a stillImageOutPut
lazy var stillImageOutPut: AVCaptureStillImageOutput = {
let imageOutPut = AVCaptureStillImageOutput.init()
return imageOutPut
}()
2 add to session
if session.canAddOutput(stillImageOutPut){
session.addOutput(stillImageOutPut)
}
3 then implement this delegate function
// MARK: AVCaptureMetadataOutputObjectsDelegate
extension ZHFaceDetectorViewController: AVCaptureMetadataOutputObjectsDelegate {
func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) {
printLog(Thread.current)
let metadataObject = metadataObjects.first
if let object = metadataObject {
while !hasDetectorFace {
if object.type == AVMetadataObject.ObjectType.face{
hasDetectorFace = true
DispatchQueue.global().async {
if let stillImageConnection = self.stillImageOutPut.connection(with: AVMediaType.video){
printLog(stillImageConnection)
printLog(connection)
stillImageConnection.videoOrientation = AVCaptureVideoOrientation(rawValue: UIDevice.current.orientation.rawValue)!
/// prepare settings 如果不设置 截取照片时屏幕会闪白
let settings = AVCaptureAutoExposureBracketedStillImageSettings.autoExposureSettings(exposureTargetBias: AVCaptureDevice.currentExposureTargetBias)
/// begin capture
self.stillImageOutPut.prepareToCaptureStillImageBracket(from: stillImageConnection, withSettingsArray: [settings], completionHandler: { (complete, error) in
if error == nil {
self.stillImageOutPut.captureStillImageAsynchronously(from: stillImageConnection, completionHandler: { (imageDataSampleBuffer, error) in
printLog(imageDataSampleBuffer)
printLog(error)
if error == nil {
if let sampleBuffer = imageDataSampleBuffer {
if let imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(sampleBuffer){
if let image = UIImage(data: imageData) {
/// operater your image
printLog(image)
}
}
}
}else{
printLog("something was wrong")
}
})
}
})
}
}
}
}
}
}
}
4 then i get my picture
log info