ios catturare un'immagine utilizzando AVFramework

Question

sto catturare immagini utilizzando questo codice

#pragma mark - image capture 

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

    // Create the session 
    AVCaptureSession *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 = AVCaptureSessionPresetMedium; 

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

    // Create a device input with the device and add it to the session. 
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device 
                    error:&error]; 
    if (!input) 
    { 
     NSLog(@"PANIC: no media input"); 
    } 
    [session addInput:input]; 

    // Create a VideoDataOutput and add it to the session 
    AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init]; 
    [session addOutput:output]; 

    // Configure your output. 
    dispatch_queue_t queue = dispatch_queue_create("myQueue", NULL); 
    [output setSampleBufferDelegate:self queue:queue]; 
    dispatch_release(queue); 

    // Specify the pixel format 
    output.videoSettings = 
    [NSDictionary dictionaryWithObject: 
    [NSNumber numberWithInt:kCVPixelFormatType_32BGRA] 
          forKey:(id)kCVPixelBufferPixelFormatTypeKey]; 


    // If you wish to cap the frame rate to a known value, such as 15 fps, set 
    // minFrameDuration. 

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

    // Assign session to an ivar. 
    [self setSession:session]; 
} 




// Delegate routine that is called when a sample buffer was written 
- (void)captureOutput:(AVCaptureOutput *)captureOutput 
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer 
    fromConnection:(AVCaptureConnection *)connection 
{ 
    NSLog(@"captureOutput: didOutputSampleBufferFromConnection"); 

    // Create a UIImage from the sample buffer data 
    UIImage *image = [self imageFromSampleBuffer:sampleBuffer]; 

    //< Add your code here that uses the image > 
    [self.imageView setImage:image]; 
    [self.view setNeedsDisplay]; 
} 


// Create a UIImage from sample buffer data 
- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer 
{ 
    NSLog(@"imageFromSampleBuffer: called"); 
    // Get a CMSampleBuffer's Core Video image buffer for the media data 
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer); 
    // Lock the base address of the pixel buffer 
    CVPixelBufferLockBaseAddress(imageBuffer, 0); 

    // Get the number of bytes per row for the pixel buffer 
    void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer); 

    // Get the number of bytes per row for the pixel buffer 
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer); 
    // Get the pixel buffer width and height 
    size_t width = CVPixelBufferGetWidth(imageBuffer); 
    size_t height = CVPixelBufferGetHeight(imageBuffer); 

    // Create a device-dependent RGB color space 
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 

    // Create a bitmap graphics context with the sample buffer data 
    CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8, 
              bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst); 
    // Create a Quartz image from the pixel data in the bitmap graphics context 
    CGImageRef quartzImage = CGBitmapContextCreateImage(context); 
    // Unlock the pixel buffer 
    CVPixelBufferUnlockBaseAddress(imageBuffer,0); 


    // Free up the context and color space 
    CGContextRelease(context); 
    CGColorSpaceRelease(colorSpace); 

    // Create an image object from the Quartz image 
    UIImage *image = [UIImage imageWithCGImage:quartzImage]; 

    // Release the Quartz image 
    CGImageRelease(quartzImage); 

    return (image); 
} 

-(void)setSession:(AVCaptureSession *)session 
{ 
    NSLog(@"setting session..."); 
    self.captureSession=session; 
} 

codice Cattura funziona. Ma! Ho bisogno di cambiare alle cose: - flusso video dalla fotocamera a mio avviso. - ottenendo immagini ogni (ad esempio 5 secondi) da esso. Aiutatemi per favore, come può essere fatto?

Answer 1

Aggiungere la seguente riga

output.minFrameDuration = CMTimeMake(5, 1); 

sotto il commento

// If you wish to cap the frame rate to a known value, such as 15 fps, set 
// minFrameDuration. 

ma soprattutto la

[session startRunning]; 

Modifica

Utilizzare il codice seguente per visualizzare in anteprima l'output della fotocamera.

AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session]; 
UIView *aView = self.view; 
CGRect videoRect = CGRectMake(0.0, 0.0, 320.0, 150.0); 
previewLayer.frame = videoRect; // Assume you want the preview layer to fill the view. 
[aView.layer addSublayer:previewLayer]; 

Edit 2: bene Ok ..

Apple ha fornito un modo per impostare il minFrameDuration here

Così ora, utilizzare il seguente codice per impostare la durata dei fotogrammi

AVCaptureConnection *conn = [output connectionWithMediaType:AVMediaTypeVideo]; 

if (conn.supportsVideoMinFrameDuration) 
    conn.videoMinFrameDuration = CMTimeMake(5,1); 
if (conn.supportsVideoMaxFrameDuration) 
    conn.videoMaxFrameDuration = CMTimeMake(5,1); 

Answer 2

Fare attenzione: la richiamata da AVCaptureOutput viene registrata nella coda di invio yo hai specificato Ho visto che esegui gli aggiornamenti dell'interfaccia utente da questa richiamata, e questo è sbagliato. Dovresti eseguirli solo nella coda principale. Per esempio.

- (void)captureOutput:(AVCaptureOutput *)captureOutput 
    didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer 
     fromConnection:(AVCaptureConnection *)connection 
{ 
    NSLog(@"captureOutput: didOutputSampleBufferFromConnection"); 
    // Create a UIImage from the sample buffer data 
    UIImage *image = [self imageFromSampleBuffer:sampleBuffer]; 
    dispatch_async(dispatch_get_main_queue(), ^{ 
    //< Add your code here that uses the image > 
     [self.imageView setImage:image]; 
     [self.view setNeedsDisplay]; 
    } 
} 

Answer 3

E qui è una versione Swift della funzione imageFromSampleBuffer:

func imageFromSampleBuffer(sampleBuffer:CMSampleBuffer!) -> UIImage { 
    let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)! 
    CVPixelBufferLockBaseAddress(imageBuffer, 0) 

    let baseAddress = CVPixelBufferGetBaseAddress(imageBuffer) 
    let bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer) 
    let width = CVPixelBufferGetWidth(imageBuffer) 
    let height = CVPixelBufferGetHeight(imageBuffer) 

    let colorSpace = CGColorSpaceCreateDeviceRGB() 

    let bitmapInfo:CGBitmapInfo = [.ByteOrder32Little, CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedFirst.rawValue)] 
    let context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, bitmapInfo.rawValue) 

    let quartzImage = CGBitmapContextCreateImage(context) 
    CVPixelBufferUnlockBaseAddress(imageBuffer, 0) 

    let image = UIImage(CGImage: quartzImage!) 
    return image 
} 

Sopra lavorare per me con i seguenti impostazioni video:

videoDataOutput = AVCaptureVideoDataOutput() 
videoDataOutput?.videoSettings = [kCVPixelBufferPixelFormatTypeKey:Int(kCVPixelFormatType_32BGRA)] 
      videoDataOutput?.setSampleBufferDelegate(self, queue: queue)