iphone - 如何从 iPhone cam 实时获取 FNumber 和 ISOSpeedRatings

Question

我需要实时获取相机参数（exif 数据），例如 FNumber、ISOSpeedRatings，而无需拍摄真实照片。有没有办法做到这一点？

Answer 1

这是完整的解决方案。不要忘记导入适当的框架和标题。

#import <AVFoundation/AVFoundation.h>
#import <ImageIO/CGImageProperties.h>

AVCaptureStillImageOutput *stillImageOutput;
AVCaptureSession *session;    

- (void)viewDidLoad
    {
        [super viewDidLoad];
        [self setupCaptureSession];
        // Do any additional setup after loading the view, typically from a nib.    
    }

    -(void)captureNow{


        AVCaptureConnection *videoConnection = nil;
        for (AVCaptureConnection *connection in stillImageOutput.connections)
        {
            for (AVCaptureInputPort *port in [connection inputPorts])
            {
                if ([[port mediaType] isEqual:AVMediaTypeVideo] )
                {
                    videoConnection = connection;
                    break;
                }
            }
            if (videoConnection) { break; }
        }

        [stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection
         completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *__strong error) {
            CFDictionaryRef exifAttachments = CMGetAttachment( imageDataSampleBuffer, kCGImagePropertyExifDictionary, NULL);
            if (exifAttachments)
            {
                // Do something with the attachments.
                NSLog(@"attachements: %@", exifAttachments);
            }
            else
              NSLog(@"no attachments");

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

    }


    // Create and configure a capture session and start it running
    - (void)setupCaptureSession
    {
        NSError *error = nil;

        // Create the session
        session = [[AVCaptureSession alloc] init];

        // Configure the session to produce lower resolution video frames, if your
        // processing algorithm can cope. We'll specify medium quality for the
        // chosen device.
        session.sessionPreset = AVCaptureSessionPreset352x288;

        // Find a suitable AVCaptureDevice
        AVCaptureDevice *device = [AVCaptureDevice
                                   defaultDeviceWithMediaType:AVMediaTypeVideo];
        [device lockForConfiguration:nil];

        device.whiteBalanceMode = AVCaptureWhiteBalanceModeLocked;
        device.focusMode = AVCaptureFocusModeLocked;
        [device unlockForConfiguration];

        // Create a device input with the device and add it to the session.
        AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device
                                                                            error:&error];
        if (!input) {
            // Handling the error appropriately.
        }
        [session addInput:input];




        stillImageOutput = [AVCaptureStillImageOutput new];
        NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys: AVVideoCodecJPEG, AVVideoCodecKey, nil];
        [stillImageOutput setOutputSettings:outputSettings];
        if ([session canAddOutput:stillImageOutput])
            [session addOutput:stillImageOutput];


        // Start the session running to start the flow of data
        [session startRunning];
        [self captureNow];

    }