我正在解决扫描前置摄像头输入的面部任务，检测它们并将它们作为 UIImage 对象获取。 我正在使用 AVFoundation 扫描和检测人脸。

像这样:

let input = try AVCaptureDeviceInput(device: captureDevice)
captureSession = AVCaptureSession()
captureSession!.addInput(input)

output = AVCaptureMetadataOutput()
captureSession?.addOutput(output)

output.setMetadataObjectsDelegate(self, queue: dispatch_get_main_queue())
output.metadataObjectTypes = [AVMetadataObjectTypeFace]


videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
videoPreviewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
videoPreviewLayer?.frame = view.layer.bounds
view.layer.addSublayer(videoPreviewLayer!)

captureSession?.startRunning()

在委托(delegate)方法 didOutputMetadataObjects 中，我得到了 AVMetadataFaceObject 的脸，并像这样用红框突出显示它:

let metadataObj = metadataObjects[0] as! AVMetadataFaceObject
let faceObject = videoPreviewLayer?.transformedMetadataObjectForMetadataObject(metadataObj)
faceFrame?.frame = faceObject!.bounds

问题是:如何获取 UIImages 的面孔？

我试图在“didOutputSampleBuffer”上跳舞，但它根本没有被调用 :c

最佳答案

我使用 didOutputSampleBuffer 和 Objective-C 做了同样的事情。看起来像:

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
  CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
  CFDictionaryRef attachments = CMCopyDictionaryOfAttachments(kCFAllocatorDefault, sampleBuffer, kCMAttachmentMode_ShouldPropagate);
  CIImage *ciImage = [[CIImage alloc] initWithCVPixelBuffer:pixelBuffer options:(__bridge NSDictionary *)attachments];
  if (attachments)
    CFRelease(attachments);

  NSNumber *orientation = (__bridge NSNumber *)(CMGetAttachment(imageDataSampleBuffer, kCGImagePropertyOrientation, NULL));
  NSArray *features = [[CIDetector detectorOfType:CIDetectorTypeFace context:nil options:@{ CIDetectorAccuracy: CIDetectorAccuracyHigh }] featuresInImage:ciImage options:@{ CIDetectorImageOrientation: orientation }];
  if (features.count == 1) {
    CIFaceFeature *faceFeature = [features firstObject];
    CGRect faceRect = faceFeature.bounds;

    CGImageRef tempImage = [[CIContext contextWithOptions:nil] createCGImage:ciImage fromRect:ciImage.extent];
    UIImage *image = [UIImage imageWithCGImage:tempImage scale:1.0 orientation:orientation.intValue];
    UIImage *face = [image extractFace:faceRect];
  }  
}

其中 extractFace 是 UIImage 的扩展:

- (UIImage *)extractFace:(CGRect)rect {
  rect = CGRectMake(rect.origin.x * self.scale,
                  rect.origin.y * self.scale,
                  rect.size.width * self.scale,
                  rect.size.height * self.scale);
  CGImageRef imageRef = CGImageCreateWithImageInRect(self.CGImage, rect);
  UIImage *result = [UIImage imageWithCGImage:imageRef scale:self.scale orientation:self.imageOrientation];
  CGImageRelease(imageRef);
  return result;
}

创建视频输出:

AVCaptureVideoDataOutput *videoOutput = [[AVCaptureVideoDataOutput alloc] init];
videoOutput.videoSettings = @{ (id)kCVPixelBufferPixelFormatTypeKey: [NSNumber numberWithInt:kCMPixelFormat_32BGRA] };
videoOutput.alwaysDiscardsLateVideoFrames = YES;
self.videoOutputQueue = dispatch_queue_create("OutputQueue", DISPATCH_QUEUE_SERIAL);
[videoOutput setSampleBufferDelegate:self queue:self.videoOutputQueue];
[self.session addOutput:videoOutput];

关于ios - (如何)从输入到前置摄像头获取人脸作为 UIImage，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/36769648/