iOS利用摄像头获取环境光感参数

不多说，代码如下：   
#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
  注意点：   
首先引入AVFoundation框架和ImageIO/ImageIO.h声明文件   
遵循AVCaptureVideoDataOutputSampleBufferDelegate协议  
AVCaptureSession对象要定义为属性，确保有对象在一直引用AVCaptureSession对象；否则如果在lightSensitive方法中定义并初始化AVCaptureSession对象，会造成AVCaptureSession对象提前释放，    [self.session startRunning];会失效   
实现AVCaptureVideoDataOutputSampleBufferDelegate的代理方法，参数brightnessValue就是周围环境的亮度参数了，范围大概在-5~~12之间,参数数值越大，环境越亮