ios - 如何使用AVCaptureStillImageOutput拍照

Question

我有一个从相机中拉出并按预期工作的预览层。我希望能够在按下按钮时拍照。我已经像这样初始化了 AVCaptureStillImageOutput:

AVCaptureStillImageOutput *avCaptureImg = [[AVCaptureStillImageOutput alloc] init];

然后我尝试使用这个对象拍照:

[avCaptureImg captureStillImageAsynchronouslyFromConnection:(AVCaptureConnection *) completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {  }];

我需要有关如何拍照并将其保存在变量中的帮助。谢谢

Answer 1

您需要确保定义一个 AVCaptureVideoPreviewLayer 并将其添加到 View 层:

AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];
[self.view.layer addSublayer:captureVideoPreviewLayer];

这将连接到您的 AVCaptureDeviceInput

这是完整的解决方案:

/////////////////////////////////////////////////
////
//// Utility to find front camera
////
/////////////////////////////////////////////////
-(AVCaptureDevice *) frontFacingCameraIfAvailable{

    NSArray *videoDevices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    AVCaptureDevice *captureDevice = nil;

   for (AVCaptureDevice *device in videoDevices){

        if (device.position == AVCaptureDevicePositionFront){

            captureDevice = device;
            break;
        }
    }

    //  couldn't find one on the front, so just get the default video device.
    if (!captureDevice){

        captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    }

    return captureDevice;
}

/////////////////////////////////////////////////
////
//// Setup Session, attach Video Preview Layer
//// and Capture Device, start running session
////
/////////////////////////////////////////////////
-(void) setupCaptureSession {
    AVCaptureSession *session = [[AVCaptureSession alloc] init];
    session.sessionPreset = AVCaptureSessionPresetMedium;

    AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer    alloc] initWithSession:session];
    [self.view.layer addSublayer:captureVideoPreviewLayer];

    NSError *error = nil;
    AVCaptureDevice *device = [self frontFacingCameraIfAvailable];
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
    if (!input) {
        // Handle the error appropriately.
        NSLog(@"ERROR: trying to open camera: %@", error);
    }
    [session addInput:input];

    self.stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
    NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys: AVVideoCodecJPEG, AVVideoCodecKey, nil];
    [self.stillImageOutput setOutputSettings:outputSettings];

    [session addOutput:self.stillImageOutput];

    [session startRunning];
}


/////////////////////////////////////////////////
////
//// Method to capture Still Image from 
//// Video Preview Layer
////
/////////////////////////////////////////////////
-(void) captureNow {
    AVCaptureConnection *videoConnection = nil;
    for (AVCaptureConnection *connection in self.stillImageOutput.connections) {
        for (AVCaptureInputPort *port in [connection inputPorts]) {
            if ([[port mediaType] isEqual:AVMediaTypeVideo] ) {
                videoConnection = connection;
                break;
            }
        }
        if (videoConnection) { break; }
    }

    NSLog(@"about to request a capture from: %@", self.stillImageOutput);
    __weak typeof(self) weakSelf = self;
    [self.stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error) {

         NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];
         UIImage *image = [[UIImage alloc] initWithData:imageData];

         [weakSelf displayImage:image];
     }];
}