我在使用 AVCaptureMetadataOutput 和 rectOfInterest 时遇到了一些扫描限制问题。我已成功绘制 UIImage 以确保扫描区域正确。
但是，无论我做什么，只有当扫描项目位于屏幕的绝对中心时才有效。 它似乎忽略了我的直肠。
输出尺寸
Display size width: 414, height: 736
Percent size width: 0.724638, height: 0.407609
Crop search area: {{57, 218}, {300, 300}}
Crop search converted: {{0.29619565217391297, 0.13768115942028991}, {0.40760869565217395, 0.72463768115942029}}
这是绘制的黄色矩形
还有实际的方法。完整代码可以在这里查看 https://github.com/fbacker/react-native-camera/blob/barcode-finder/ios/RCTCameraManager.m
- (void)startSession {
#if TARGET_IPHONE_SIMULATOR
return;
#endif
dispatch_async(self.sessionQueue, ^{
if (self.presetCamera == AVCaptureDevicePositionUnspecified) {
self.presetCamera = AVCaptureDevicePositionBack;
}
AVCaptureStillImageOutput *stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
if ([self.session canAddOutput:stillImageOutput])
{
stillImageOutput.outputSettings = @{AVVideoCodecKey : AVVideoCodecJPEG};
[self.session addOutput:stillImageOutput];
self.stillImageOutput = stillImageOutput;
}
AVCaptureMovieFileOutput *movieFileOutput = [[AVCaptureMovieFileOutput alloc] init];
if ([self.session canAddOutput:movieFileOutput])
{
[self.session addOutput:movieFileOutput];
self.movieFileOutput = movieFileOutput;
}
AVCaptureMetadataOutput *metadataOutput = [[AVCaptureMetadataOutput alloc] init];
CGRect scanBarcodeArea = CGRectMake(0, 0, 0, 0);
if ([self.session canAddOutput:metadataOutput]) {
[self.session addOutput:metadataOutput];
[metadataOutput setMetadataObjectsDelegate:self queue:self.sessionQueue];
[metadataOutput setMetadataObjectTypes:self.barCodeTypes];
// we only want to scan specified area
// NOTE; Seems we can only set the actual rect after session started, else it doesn't work
if (self.barcodeFinderVisible) {
NSNumber *imageWidth = [NSNumber numberWithFloat:self.previewLayer.frame.size.width];
NSNumber *imageHeight = [NSNumber numberWithFloat:self.previewLayer.frame.size.height];
double imageUseWidth = [imageWidth doubleValue];
double imageUseHeight = [imageHeight doubleValue];
double cropWidth = imageUseWidth * self.barcodeFinderPercentageSizeWidth;
double cropHeight = imageUseHeight * self.barcodeFinderPercentageSizeHeight;
double cropX = (imageUseWidth/2)-(cropWidth/2);
double cropY = (imageUseHeight/2)-(cropHeight/2);
CGRect scanLimit = CGRectMake(cropX, cropY, cropWidth, cropHeight);
scanBarcodeArea = [_previewLayer metadataOutputRectOfInterestForRect:scanLimit];
[metadataOutput setRectOfInterest:scanBarcodeArea];
/* ############################
DEBUG PURPOSE, get some values and draw yellow rect of actual scanning area
*/
/*
NSLog(@"Display size width: %@, height: %@", imageWidth, imageHeight);
NSLog(@"
ercent size width: %f, height: %f", self.barcodeFinderPercentageSizeWidth, self.barcodeFinderPercentageSizeHeight);
NSLog(@"Crop search area: %@", NSStringFromCGRect(scanLimit));
NSLog(@"Crop search converted: %@", NSStringFromCGRect(scanBarcodeArea));
// PAUSE AND PLAY WILL DRAW YELLOW RECT, IF VALID, might appear auto as well. who knows.
UIView *scanAreaView = [[UIView alloc] initWithFrame:scanLimit];
scanAreaView.layer.borderColor = [UIColor yellowColor].CGColor;
scanAreaView.layer.borderWidth = 4;
[self.view addSubview:scanAreaView];
*/
}
}
self.metadataOutput = metadataOutput;
__weak RCTCameraManager *weakSelf = self;
[self setRuntimeErrorHandlingObserver:[NSNotificationCenter.defaultCenter addObserverForName:AVCaptureSessionRuntimeErrorNotification object:self.session queue:nil usingBlock:^(NSNotification *note) {
RCTCameraManager *strongSelf = weakSelf;
dispatch_async(strongSelf.sessionQueue, ^{
// Manually restarting the session since it must have been stopped due to an error.
[strongSelf.session startRunning];
});
}]];
[self.session startRunning];
});
}
据我所知，
scanBarcodeArea = [_previewLayer metadataOutputRectOfInterestForRect:scanLimit];
[metadataOutput setRectOfInterest:scanBarcodeArea];
此代码不能总是返回正确的矩形，有时返回 {{0,0},{0,0}}，因为我使用矩形导航，当我导航到相机屏幕，然后返回，并导航到相机再次，我得到了 {{0,0},{0,0}}，有人说 previewLayer 没有初始好。
即使我把这段代码放在
之后[self.session startRunning];
当我第一次运行我的应用程序并第一次导航到相机屏幕时，也会得到 {{0,0},{0,0}}。
所以，我使用这些打击代码而不是 metadataOutputRectOfInterestForRect: 来计算矩形范围。
NSNumber *imageWidth = [NSNumber numberWithFloat:self.previewLayer.frame.size.width];
NSNumber *imageHeight = [NSNumber numberWithFloat:self.previewLayer.frame.size.height];
double imageUseWidth = [imageWidth doubleValue];
double imageUseHeight = [imageHeight doubleValue];
double cropWidth = imageUseWidth * self.barcodeFinderPercentageSizeWidth;
double cropHeight = imageUseHeight * self.barcodeFinderPercentageSizeHeight;
double cropX = (imageUseWidth/2)-(cropWidth/2);
double cropY = ((imageUseHeight)/2)-(cropHeight/2);
// transform to camera coordinate
double scanX = cropY / imageUseHeight;
double scanY = cropX / imageUseWidth;
double scanWidth = cropHeight / imageUseHeight;
double scanHeight = cropWidth / imageUseWidth;
CGRect rectOfInterest = CGRectMake(scanX, scanY, scanWidth, scanHeight);
关于ios rectOfInterest AVCaptureMetadataOutput 忽略，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47817616/
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