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