iOSスイープ弱光検出

 ：AVCaptureVideoDataOutputSampleBufferDelegate

 //  
AVCaptureVideoDataOutput *buffer = [[AVCaptureVideoDataOutput alloc] init];
[buffer setSampleBufferDelegate:self queue:dispatch_get_main_queue()];

if ([self.session canAddOutput:buffer]) [self.session addOutput:buffer];

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
    
    static BOOL isStop = false;
    if (isStop) return;
    
    isStop = true;
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        
        isStop = false;
    });
    
    CFDictionaryRef metadataDict = CMCopyDictionaryOfAttachments(NULL,sampleBuffer, kCMAttachmentMode_ShouldPropagate);
    NSDictionary *metadata = [[NSMutableDictionary alloc] initWithDictionary:(__bridge NSDictionary*)metadataDict];
    CFRelease(metadataDict);
    NSDictionary *exifMetadata = [[metadata objectForKey:(NSString *)kCGImagePropertyExifDictionary] mutableCopy];
    float brightnessValue = [[exifMetadata objectForKey:(NSString *)kCGImagePropertyExifBrightnessValue] floatValue];
    
    UIButton *lightBtn = [self.view viewWithTag:111111];
    if (brightnessValue < 0 && !lightBtn.selected && lightBtn.isHidden) {
        
        [lightBtn.layer removeAllAnimations];
        lightBtn.hidden = false;
        [lightBtn alphaOrOpacityAnimation]; //  
    }
    
    if (brightnessValue > 0 && !lightBtn.selected && !lightBtn.isHidden) {
        
        [lightBtn.layer removeAllAnimations];
        lightBtn.hidden = true;
    }
}

//  
- (void)alphaOrOpacityAnimation {
    
    CABasicAnimation *animation =[CABasicAnimation animationWithKeyPath:@"opacity"];
    animation.fromValue = [NSNumber numberWithFloat:1.0f];
    animation.toValue = [NSNumber numberWithFloat:0.1f];  //  。
    animation.autoreverses = YES;
    animation.duration = 0.75;
    animation.repeatCount = 2;
    animation.removedOnCompletion = NO;
    animation.fillMode = kCAFillModeForwards;  //removedOnCompletion,fillMode 
    animation.timingFunction=[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];
    
    [self.layer addAnimation:animation forKey:nil];
}

// 
- (void)lightBtnOnClick:(UIButton *)btn
{
    [btn.layer removeAllAnimations];
    
    // ppExt： _device： 
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    
    // 
    if (![device hasTorch]) {
        
        [self skipToApplicationSettingWith:Error_Torch_Failure IsToSetting:false CancelHanlder:nil];
        return;
    }
    
    btn.selected = !btn.selected;
    
    [device lockForConfiguration:nil];
    if (btn.selected) {
        
        [device setTorchMode:AVCaptureTorchModeOn];
    }else
    {
        [device setTorchMode:AVCaptureTorchModeOff];
    }
    [device unlockForConfiguration];
}