AVCaptureMetadataOutput, rectOfInterest scans outside - ios

Question

So I'm trying AVCaptureMetadataOutput for scanning QR-codes. The problem I have is that the scanning can occur outside the preview area even though I use rectOfInterest see image below:
Here's the code:
- (void)capture
{
session = [[AVCaptureSession alloc] init];
device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
if ( [device lockForConfiguration:NULL] == YES ) {
CGPoint point = CGPointMake(0.5,0.5);
[device setFocusPointOfInterest:point];
[device setFocusMode:AVCaptureFocusModeContinuousAutoFocus];
[device unlockForConfiguration];
}
NSError *error = nil;
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device
error:&error];
if (!input)
{
NSLog(#"Error: %#", error);
return;
}
[session addInput:input];
//Add the metadata output device
output = [[AVCaptureMetadataOutput alloc] init];
[output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
[session addOutput:output];
output.metadataObjectTypes = #[AVMetadataObjectTypeQRCode, AVMetadataObjectTypeCode128Code];
output.rectOfInterest = self.livevideo.bounds;
newCaptureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];
newCaptureVideoPreviewLayer.frame = self.livevideo.bounds;
newCaptureVideoPreviewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
[self.livevideo.layer insertSublayer:newCaptureVideoPreviewLayer above:self.livevideo.layer];
highlightView = [[UIView alloc] init];
highlightView.autoresizingMask = UIViewAutoresizingFlexibleTopMargin|UIViewAutoresizingFlexibleLeftMargin|UIViewAutoresizingFlexibleRightMargin|UIViewAutoresizingFlexibleBottomMargin;
highlightView.layer.borderColor = [UIColor greenColor].CGColor;
highlightView.layer.borderWidth = 3;
[self.livevideo addSubview:highlightView];
[session startRunning];
}
- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputMetadataObjects:(NSArray *)metadataObjects
fromConnection:(AVCaptureConnection *)connection
{
AVMetadataMachineReadableCodeObject *barCodeObject;
CGRect highlightViewRect = CGRectZero;
for (AVMetadataObject *metadata in metadataObjects)
{
for (NSString *type in output.metadataObjectTypes) {
if ([metadata.type isEqualToString:type])
{
barCodeObject = (AVMetadataMachineReadableCodeObject *)[newCaptureVideoPreviewLayer transformedMetadataObjectForMetadataObject:(AVMetadataMachineReadableCodeObject *)metadata];
highlightViewRect = barCodeObject.bounds;
#try {
NSString *code =[barCodeObject stringValue];
NSLog(#"Read type: %#", type);
self.barcode.text = code;
}
#catch (NSException *exception) {
NSLog(#"%#", exception.reason);
}
break;
}
}
}
highlightView.frame = highlightViewRect;
}

Answer 1

That is the documented behavior:
Metadata objects whose bounds do not intersect with the rectOfInterest will not be returned.
So, if the QR code at all intersects the rectangle, it will be detected.