Hi I want to setup AV
capture session to capture images with specific resolution (and, if possible, with specific quality) using iphone camera. here's setupping AV
session code
// 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];
}
and 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];
}
and output methods:
// 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);
}
Everything is quite standard. But where and what should I change to specify the resolution of captured image and it's quality. Help me please
Refer to Apple's guide Capturing Still Images section regarding which sizes you'll get if you set one or another preset.
The parameter you should change is captureSession.sessionPreset