AVCaptureSession especifica la resolución y la calidad de las imágenes capturadas obj-c iphone app

Question

Hola quiero configurar AV captura de sesión para capturar imágenes con resolución específica (y, si es posible, con calidad específica) usando la cámara iphone. aquí está 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 salida métodos:

// 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 debería cambiar para especificar la resolución de la imagen capturada y su calidad. Ayuda por favor

Answer 1

Consulte Apple's guide capturando imágenes fijas sección con respecto a los tamaños que obtendrá si establece uno u otro preajuste.

El parámetro que debe cambiar es captureSession.sessionPreset

Answer 2

tratar de 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];