iOS利用摄像头获取环境光感参数的方法

#import "LightSensitiveViewController.h"

@import AVFoundation;

#import <ImageIO/ImageIO.h>

@interface LightSensitiveViewController ()< AVCaptureVideoDataOutputSampleBufferDelegate>

@property (nonatomic, strong) AVCaptureSession *session;

@end

@implementation LightSensitiveViewController

- (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view.
  self.view.backgroundColor = [UIColor whiteColor];

  self.navigationItem.title = @"光感";
  [self lightSensitive];
}

- (void)didReceiveMemoryWarning {
  [super didReceiveMemoryWarning];
  // Dispose of any resources that can be recreated.
}

#pragma mark- 光感
- (void)lightSensitive {

  // 1.获取硬件设备
  AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

  // 2.创建输入流
  AVCaptureDeviceInput *input = [[AVCaptureDeviceInput alloc]initWithDevice:device error:nil];

  // 3.创建设备输出流
  AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init];
  [output setSampleBufferDelegate:self queue:dispatch_get_main_queue()];


  // AVCaptureSession属性
  self.session = [[AVCaptureSession alloc]init];
  // 设置为高质量采集率
  [self.session setSessionPreset:AVCaptureSessionPresetHigh];
  // 添加会话输入和输出
  if ([self.session canAddInput:input]) {
    [self.session addInput:input];
  }
  if ([self.session canAddOutput:output]) {
    [self.session addOutput:output];
  }

  // 9.启动会话
  [self.session startRunning];

}

#pragma mark- AVCaptureVideoDataOutputSampleBufferDelegate的方法
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {

  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];

  NSLog(@"%f",brightnessValue);


  // 根据brightnessValue的值来打开和关闭闪光灯
  AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
  BOOL result = [device hasTorch];// 判断设备是否有闪光灯
  if ((brightnessValue < 0) && result) {// 打开闪光灯

    [device lockForConfiguration:nil];

    [device setTorchMode: AVCaptureTorchModeOn];//开

    [device unlockForConfiguration];

  }else if((brightnessValue > 0) && result) {// 关闭闪光灯

    [device lockForConfiguration:nil];
    [device setTorchMode: AVCaptureTorchModeOff];//关
    [device unlockForConfiguration];

  }

}

@end