AvCapturesession especifique la resolución y la calidad de las imágenes capturadas OBJ-C iPhone App

Question

Hola quiero configurar AV Captura la sesión para capturar imágenes con resolución específica (y, si es posible, con calidad específica) usando la cámara de iPhone. Aquí hay setupping AV código de sesión

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

    // Create the session
    self.captureSession = [[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.
    captureSession.sessionPreset = AVCaptureSessionPresetMedium;

    // Find a suitable AVCaptureDevice
    NSArray *cameras=[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    AVCaptureDevice *device;
    if ([UserDefaults camera]==UIImagePickerControllerCameraDeviceFront)
    {
        device =[cameras objectAtIndex:1];
    }
    else
    {
        device = [cameras objectAtIndex:0];
    };

    // 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");
    }
    [captureSession addInput:input];

    // Create a VideoDataOutput and add it to the session
    AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init];
    [captureSession addOutput:output];
    NSLog(@"connections: %@", output.connections);

    // 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.


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

y setSession:

-(void)setSession:(AVCaptureSession *)session
{
    NSLog(@"setting session...");
    self.captureSession=session;
    NSLog(@"setting camera view");
    self.previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session];
    //UIView *aView = self.view;
    CGRect videoRect = CGRectMake(20.0, 20.0, 280.0, 255.0);
    previewLayer.frame = videoRect; // Assume you want the preview layer to fill the view.
    [previewLayer setBackgroundColor:[[UIColor grayColor] CGColor]];
    [self.view.layer addSublayer:previewLayer];
    //[aView.layer addSublayer:previewLayer];
}

y métodos de salida:

// 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
    self.currentImage = [self imageFromSampleBuffer:sampleBuffer];

    //< Add your code here that uses the image >
}

// 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);
}

Todo es bastante estándar. Pero dónde y qué debo cambiar para especificar la resolución de la imagen capturada y su calidad. Ayudame por favor

Answer 1

Referirse a Guía de Apple Captura de la sección de imágenes fijas sobre qué tamaños obtendrá si establece uno u otro preajuste.

El parámetro que debe cambiar es captureSession.sessionPreset

Answer 2

Intente ir con algo como esto donde CX y CY son sus resoluciones personalizadas:

NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                              AVVideoScalingModeResizeAspectFill,AVVideoScalingModeKey,
                           AVVideoCodecH264, AVVideoCodecKey,
                           [NSNumber numberWithInt:cx], AVVideoWidthKey,
                           [NSNumber numberWithInt:cx], AVVideoHeightKey,
                           nil];
_videoInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];