How to focus the near by objects in iOS 8? - ios

Question

I'm developing a QR code reader. My Codes are 1cm long and width. I'm using AVFoundation metadata to capture the machine readable codes and it works fine. But at the same time i need to take a picture of the QR code with the logo (Which is located in mid of the QR code). So I'm using AVCaptureVideoDataOutput and didOutputSampleBuffer to get the image stills. The problem comes in clarity of the image. it looks always blurry in the edges of the codes and logo. So i did a research on manual controls in and made some code changes for manual focusing but no luck till now.
How to focus (which is 10cm away from the camera and tiny)the near by objects?
Do we have any other way of getting the image after successful scan from the metadata?
What is difference between setFocusModeLockedWithLensPosition and focusPointOfInterest ?
Here is my code (part of it)
// 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 = AVCaptureSessionPresetHigh;
// Find a suitable AVCaptureDevice
_device = [AVCaptureDevice
defaultDeviceWithMediaType:AVMediaTypeVideo];
if ([_device lockForConfiguration:&error]) {
[_device setAutoFocusRangeRestriction:AVCaptureAutoFocusRangeRestrictionNone];
[_device setFocusModeLockedWithLensPosition:0.5 completionHandler:nil];
//[device setFocusMode:AVCaptureFocusModeAutoFocus];
// _device.focusPointOfInterest = CGPointMake(0.5,0.5);
// device.videoZoomFactor = 1.0 + 10;
[_device unlockForConfiguration];
}
// if ([_device isSmoothAutoFocusEnabled])
// {
// _device.smoothAutoFocusEnabled = NO;
// }
// 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];
// For scanning QR code
AVCaptureMetadataOutput *metaDataOutput = [[AVCaptureMetadataOutput alloc] init];
// Have to add the output before setting metadata types
[_session addOutput:metaDataOutput];
[metaDataOutput setMetadataObjectTypes:#[AVMetadataObjectTypeQRCode]];
[metaDataOutput setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
//For saving the image to camera roll
_stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys: AVVideoCodecJPEG, AVVideoCodecKey, nil];
[_stillImageOutput setOutputSettings:outputSettings];
[_session addOutput:_stillImageOutput];
// 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];
// Specify the pixel format
output.videoSettings =
[NSDictionary dictionaryWithObject:
[NSNumber numberWithInt:kCVPixelFormatType_32BGRA]
forKey:(id)kCVPixelBufferPixelFormatTypeKey];
// Start the session running to start the flow of data
[self startCapturingWithSession:_session];
// Assign session to an ivar.
[self setSession:_session];
}
- (void)startCapturingWithSession: (AVCaptureSession *) captureSession
{
NSLog(#"Adding video preview layer");
[self setPreviewLayer:[[AVCaptureVideoPreviewLayer alloc] initWithSession:captureSession]];
[self.previewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
//----- DISPLAY THE PREVIEW LAYER -----
//Display it full screen under out view controller existing controls
NSLog(#"Display the preview layer");
CGRect layerRect = [[[self view] layer] bounds];
[self.previewLayer setBounds:layerRect];
[self.previewLayer setPosition:CGPointMake(CGRectGetMidX(layerRect),
CGRectGetMidY(layerRect))];
[self.previewLayer setAffineTransform:CGAffineTransformMakeScale(3.5, 3.5)];
//[[[self view] layer] addSublayer:[[self CaptureManager] self.previewLayer]];
//We use this instead so it goes on a layer behind our UI controls (avoids us having to manually bring each control to the front):
UIView *CameraView = [[UIView alloc] init];
[[self view] addSubview:CameraView];
[self.view sendSubviewToBack:CameraView];
[[CameraView layer] addSublayer:self.previewLayer];
//----- START THE CAPTURE SESSION RUNNING -----
[captureSession startRunning];
[self switchONFlashLight];
}
// Delegate routine that is called when a sample buffer was written
- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
fromConnection:(AVCaptureConnection *)connection
{
// Create a UIImage from the sample buffer data
[connection setVideoOrientation:AVCaptureVideoOrientationLandscapeLeft];
UIImage *image = [self imageFromSampleBuffer:sampleBuffer];
}
/ Create a UIImage from sample buffer data
- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer
{
// 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)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection{
if (metadataObjects != nil && [metadataObjects count] > 0) {
AVMetadataMachineReadableCodeObject *metadataObj = [metadataObjects objectAtIndex:0];
// if ([_device lockForConfiguration:nil]){
// [_device setAutoFocusRangeRestriction:AVCaptureAutoFocusRangeRestrictionNear];
// _device.focusPointOfInterest = CGPointMake(metadataObj.bounds.origin.x, metadataObj.bounds.origin.y);
// [_device unlockForConfiguration];
// }
if ([[metadataObj type] isEqualToString:AVMetadataObjectTypeQRCode]) {
[_lblStatus performSelectorOnMainThread:#selector(setText:) withObject:[metadataObj stringValue] waitUntilDone:NO];
}
}
}
Aiming for iOS 8 and latest iPhones only.

Answer 1

After did regressive research and got inputs from photographers. I'm sharing my answers for the future readers.
As of iOS 8 apple provides only three focus modes. Which are
typedef NS_ENUM(NSInteger, AVCaptureFocusMode) {
AVCaptureFocusModeLocked = 0,
AVCaptureFocusModeAutoFocus = 1,
AVCaptureFocusModeContinuousAutoFocus = 2,
} NS_AVAILABLE(10_7, 4_0);
To focus an object which is very near to the lens we can use AVCaptureAutoFocusRangeRestrictionNear
but for my need due to restrictions on minimum focus length with the iPhone cameras it is not possible to get the clear image of my codes.
AFAIK there is no way to get image data from metadata. My question itself wrong. but how ever you can get the image buffers from video frames. check out Capturing Video Frames as UIImage Objects for more info.
setFocusModeLockedWithLensPosition will lock the focus mode and will allow us to set the particular lens position which starts from 0.0 to 1.0.
focusPointOfInterest dont change the focus mode but it will just set points for focus. Best example would be tap to focus.