Xcode AVCapturesession扫描特定帧中的条形码(rectOfInterest不起作用) [英] Xcode AVCapturesession scan Barcode in specific frame (rectOfInterest is not working)
问题描述
我正在尝试为当前正在使用的应用程序设计条形码扫描仪.我希望扫描仪预览可以填满设备的整个屏幕,并提供一个较小的框架来指向条形码.一切都在按我想要的方式进行,但我无法获得感兴趣的框架.
I am trying to design a barcode scanner for an App i am currently working on. I want the scanner preview to fill the whole screen of the device and provide a smaller frame to point at barcodes. All is working how i want it but i can not get the frame of interest to work.
这是条形码扫描仪的实现:
Here is the Implementation of the barcode scanner:
#import "GEScannerViewController.h"
@import AVFoundation;
@interface GEScannerViewController () <AVCaptureMetadataOutputObjectsDelegate> {
AVCaptureSession *_session;
AVCaptureDevice *_device;
AVCaptureDeviceInput *_input;
AVCaptureMetadataOutput *_output;
AVCaptureVideoPreviewLayer *_prevLayer;
UIView *_greyView;
UIView *_highlightView;
UIView *_scopeView;
UILabel *_label;
}
@end
@implementation GEScannerViewController
- (void)viewDidLoad {
[super viewDidLoad];
_label = [[UILabel alloc] init];
_label.frame = CGRectMake(0, self.view.bounds.size.height - 40, self.view.bounds.size.width, 40);
_label.autoresizingMask = UIViewAutoresizingFlexibleTopMargin;
_label.backgroundColor = [UIColor colorWithWhite:0.15 alpha:0.65];
_label.textColor = [UIColor whiteColor];
_label.textAlignment = NSTextAlignmentCenter;
_label.text = @"(none)";
[self.view addSubview:_label];
NSError *error = nil;
_session = [[AVCaptureSession alloc] init];
_device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
[_device lockForConfiguration:&error];
if (error) {
NSLog(@"Error: %@", error);
}
_device.focusPointOfInterest = CGPointMake(self.view.frame.size.width / 2, (self.view.frame.size.height / 2) - 80);
_input = [AVCaptureDeviceInput deviceInputWithDevice:_device error:&error];
if (_input) {
[_session addInput:_input];
} else {
NSLog(@"Error: %@", error);
}
_output = [[AVCaptureMetadataOutput alloc] init];
[_output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
_output.rectOfInterest = CGRectMake((self.view.frame.size.width / 2) - 160, (self.view.frame.size.height / 2) - 160, 320, 160);
[_session addOutput:_output];
_output.metadataObjectTypes = [_output availableMetadataObjectTypes];
_prevLayer = [AVCaptureVideoPreviewLayer layerWithSession:_session];
_prevLayer.frame = self.view.bounds;
_prevLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
[self.view.layer addSublayer:_prevLayer];
_greyView = [[UIView alloc] initWithFrame:self.view.frame];
_greyView.bounds = self.view.bounds;
_greyView.backgroundColor = [UIColor colorWithWhite:0.15 alpha:0.65];
[self.view.layer addSublayer:_greyView.layer];
_scopeView = [[UIView alloc] initWithFrame:CGRectMake((self.view.frame.size.width / 2) - 160, (self.view.frame.size.height / 2) - 160, 320, 160)];
_scopeView.backgroundColor = [UIColor clearColor];
_scopeView.layer.borderColor = [UIColor greenColor].CGColor;
_scopeView.layer.borderWidth = 1;
_scopeView.clipsToBounds = YES;
[self.view addSubview:_scopeView];
_highlightView = [[UIView alloc] init];
_highlightView.autoresizingMask = UIViewAutoresizingFlexibleTopMargin|UIViewAutoresizingFlexibleLeftMargin|UIViewAutoresizingFlexibleRightMargin|UIViewAutoresizingFlexibleBottomMargin;
_highlightView.layer.borderColor = [UIColor greenColor].CGColor;
_highlightView.layer.borderWidth = 3;
[_scopeView addSubview:_highlightView];
[_session startRunning];
[self.view bringSubviewToFront:_highlightView];
[self.view bringSubviewToFront:_label];
}
我正在使用_output.rectOfInterest将帧指定为与_scopeView的帧相同.不幸的是,这是行不通的.如果我这样做,将无法再识别条形码.
I am using _output.rectOfInterest to specify the frame to be the same as the _scopeView's frame. Unfortunately this is not working. No barcodes are recognized anymore if i do that.
推荐答案
一经了解,它绝对是很清楚的:
As soon as i got it, it was absolutely clear:
AVCaptureMetadataOutput由像素定义,因此要将显示的坐标映射到输出中的坐标,我不得不使用metadataOutputRectOfInterestForRect:
The AVCaptureMetadataOutput is defined by pixels, therefore to map the coordinates of the display to that in the output, i had to use metadataOutputRectOfInterestForRect:
From AVCaptureOutput.h:
/*!
@method metadataOutputRectOfInterestForRect:
@abstract
Converts a rectangle in the receiver's coordinate space to a rectangle of interest in the coordinate space of an AVCaptureMetadataOutput
whose capture device is providing input to the receiver.
@param rectInOutputCoordinates
A CGRect in the receiver's coordinates.
@result
A CGRect in the coordinate space of the metadata output whose capture device is providing input to the receiver.
@discussion
AVCaptureMetadataOutput rectOfInterest is expressed as a CGRect where {0,0} represents the top left of the picture area,
and {1,1} represents the bottom right on an unrotated picture. This convenience method converts a rectangle in
the coordinate space of the receiver to a rectangle of interest in the coordinate space of an AVCaptureMetadataOutput
whose AVCaptureDevice is providing input to the receiver. The conversion takes orientation, mirroring, and scaling into
consideration. See -transformedMetadataObjectForMetadataObject:connection: for a full discussion of how orientation and mirroring
are applied to sample buffers passing through the output.
*/
- (CGRect)metadataOutputRectOfInterestForRect:(CGRect)rectInOutputCoordinates NS_AVAILABLE_IOS(7_0);
在使用它来设置rectOfInterest之后,它就起作用了.
After using this to set the rectOfInterest it worked.
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