iOS学习笔记 摄像头

一、摄像头

在iOS中，手机摄像头的使用有以下两种方法：

1. UIImagePickerController拍照和视频录制
   • 优点：使用方便，功能强大
   • 缺点：高度封装性，无法实现一些自定义工作
2. AVFoundation框架实现
   • 优点：灵活性强，提供了很多现成的输入设备和输出设备，还有很多底层的内容可以供开发者使用
   • 缺点：需要和底层打交道，学习难度大，使用复杂

我们平常使用UIImagePickerController就基本可以满足了，功能确实强大，但它也有不好的一点，那就是由于它的高度封装性，如果要进行某些自定义工作就比较复杂，例如如果要做出一款类似于美颜相机的拍照界面就比较难以实现，这个时候就要考虑AVFoundation框架实现。

二、UIImagePickerController

UIImagePickerController继承于UINavigationController，属于UIKit框架，可以实现图片选取、拍照、录制视频等功能，使用起来十分方便。

1. 常用属性：

@property (nonatomic) UIImagePickerControllerSourceType sourceType;/* 拾取源类型枚举 */typedef NS_ENUM(NSInteger, UIImagePickerControllerSourceType) {    UIImagePickerControllerSourceTypePhotoLibrary,//照片库    UIImagePickerControllerSourceTypeCamera,//摄像头    UIImagePickerControllerSourceTypeSavedPhotosAlbum//相簿};/*   媒体类型，默认情况下此数组包含kUTTypeImage，表示拍照  如果要录像，必须设置为kUTTypeVideo（视频不带声音）或kUTTypeMovie（视频带声音）*/@property (nonatomic,copy) NSArray<NSString *> *mediaTypes;@property (nonatomic) NSTimeInterval videoMaximumDuration;//视频最大录制时长，默认10s@property (nonatomic) UIImagePickerControllerQualityType videoQuality;//视频质量typedef NS_ENUM(NSInteger, UIImagePickerControllerQualityType) {    UIImagePickerControllerQualityTypeHigh = 0,  //高清    UIImagePickerControllerQualityTypeMedium,    //中等，适合WiFi传输    UIImagePickerControllerQualityTypeLow,      //低质量，适合蜂窝网传输    UIImagePickerControllerQualityType640x480, //640*480    UIImagePickerControllerQualityTypeIFrame1280x720, //1280*720    UIImagePickerControllerQualityTypeIFrame960x540, //960*540};@property (nonatomic)  BOOL showsCameraControls;/* 是否显示摄像头控制面板，默认为YES */@property (nonatomic,strong) UIView *cameraOverlayView;/* 摄像头上覆盖的视图 */@property (nonatomic) CGAffineTransform cameraViewTransform;/* 摄像头形变 */@property (nonatomic) UIImagePickerControllerCameraCaptureMode cameraCaptureMode;/* 摄像头捕捉模式 */typedef NS_ENUM(NSInteger, UIImagePickerControllerCameraCaptureMode) {    UIImagePickerControllerCameraCaptureModePhoto,//拍照模式    UIImagePickerControllerCameraCaptureModeVideo//视频录制模式};@property (nonatomic) UIImagePickerControllerCameraDevice cameraDevice;/* 摄像头设备 */typedef NS_ENUM(NSInteger, UIImagePickerControllerCameraDevice) {    UIImagePickerControllerCameraDeviceRear,//前置摄像头    UIImagePickerControllerCameraDeviceFront//后置摄像头};@property (nonatomic) UIImagePickerControllerCameraFlashMode cameraFlashMode;/* 闪光灯模式 */typedef NS_ENUM(NSInteger, UIImagePickerControllerCameraFlashMode) {    UIImagePickerControllerCameraFlashModeOff  = -1,//关闭闪光灯    UIImagePickerControllerCameraFlashModeAuto = 0,//闪光灯自动，默认    UIImagePickerControllerCameraFlashModeOn   = 1//打开闪光灯};

2. 常用对象方法：

- (void)takePicture; //拍照                     - (BOOL)startVideoCapture;//开始录制视频- (void)stopVideoCapture;//停止录制视频

3. 代理方法：

/* 媒体获取完成会调用 */- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info;/* 取消获取会调用 */- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker;

4. 扩展函数，用于保存到相簿：

/* 保存图片到相簿 */void UIImageWriteToSavedPhotosAlbum(    UIImage *image,//保存的图片UIImage    id completionTarget,//回调的执行者    SEL completionSelector, //回调方法    void *contextInfo//回调参数信息);//上面一般保存图片的回调方法为：- (void)image:(UIImage *)image         didFinishSavingWithError:(NSError *)error         contextInfo:(void *)contextInfo;/* 判断是否能保存视频到相簿 */BOOL UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(NSString *videoPath);/* 保存视频到相簿 */void UISaveVideoAtPathToSavedPhotosAlbum(    NSString *videoPath, //保存的视频文件路径    id completionTarget, //回调的执行者    SEL completionSelector,//回调方法    void *contextInfo//回调参数信息);//上面一般保存视频的回调方法为：- (void)video:(NSString *)videoPath         didFinishSavingWithError:(NSError *)error         contextInfo:(void *)contextInfo;

5. 使用摄像头的步骤：

1. 创建UIImagePickerController对象
2. 指定拾取源，拍照和录像都需要使用摄像头
3. 指定摄像头设备，是前置的还是后置的
4. 设置媒体类型，媒体类型定义在MobileCoreServices.framework中
5. 指定摄像头捕捉模式，录像必须先设置媒体类型再设置捕捉模式。
6. 展示UIImagePickerController，通常以模态弹出形式打开
7. 拍照或录像结束后，在代理方法中展示或者保存照片或视频

6. 下面是具体实例代码：

#import "ViewController.h"#import <MobileCoreServices/MobileCoreServices.h>@interface ViewController () <UIImagePickerControllerDelegate,UINavigationControllerDelegate>@property (strong, nonatomic) UIImagePickerController *pickerController;//拾取控制器@property (strong, nonatomic) IBOutlet UIImageView *showImageView;//显示图片@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    //初始化拾取控制器    [self initPickerController];}/* 初始化拾取控制器 */- (void)initPickerController{    //创建拾取控制器    UIImagePickerController *pickerController = [[UIImagePickerController alloc] init];    //设置拾取源为摄像头    pickerController.sourceType = UIImagePickerControllerSourceTypeCamera;    //设置摄像头为后置    pickerController.cameraDevice = UIImagePickerControllerCameraDeviceRear;    pickerController.editing = YES;//设置运行编辑，即可以点击一些拾取控制器的控件    pickerController.delegate = self;//设置代理    self.pickerController = pickerController;}#pragma mark - UI点击/* 点击拍照 */- (IBAction)imagePicker:(id)sender {    //设定拍照的媒体类型    self.pickerController.mediaTypes = @[(NSString *)kUTTypeImage];    //设置摄像头捕捉模式为捕捉图片    self.pickerController.cameraCaptureMode = UIImagePickerControllerCameraCaptureModePhoto;    //模式弹出拾取控制器    [self presentViewController:self.pickerController animated:YES completion:nil];}/* 点击录像 */- (IBAction)videoPicker:(id)sender {    //设定录像的媒体类型    self.pickerController.mediaTypes = @[(NSString *)kUTTypeMovie];    //设置摄像头捕捉模式为捕捉视频    self.pickerController.cameraCaptureMode = UIImagePickerControllerCameraCaptureModeVideo;    //设置视频质量为高清    self.pickerController.videoQuality = UIImagePickerControllerQualityTypeHigh;    //模式弹出拾取控制器    [self presentViewController:self.pickerController animated:YES completion:nil];}#pragma mark - 代理方法/* 拍照或录像成功，都会调用 */- (void)imagePickerController:(UIImagePickerController *)pickerdidFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info{    //从info取出此时摄像头的媒体类型    NSString *mediaType = [info objectForKey:UIImagePickerControllerMediaType];    if ([mediaType isEqualToString:(NSString *)kUTTypeImage]) {//如果是拍照        //获取拍照的图像        UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];        //保存图像到相簿        UIImageWriteToSavedPhotosAlbum(image, self,                   @selector(image:didFinishSavingWithError:contextInfo:), nil);    } else if ([mediaType isEqualToString:(NSString *)kUTTypeMovie]) {//如果是录像        //获取录像文件路径URL        NSURL *url = [info objectForKey:UIImagePickerControllerMediaURL];        NSString *path = url.path;        //判断能不能保存到相簿        if (UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(path)) {            //保存视频到相簿            UISaveVideoAtPathToSavedPhotosAlbum(path, self,                    @selector(video:didFinishSavingWithError:contextInfo:), nil);        }    }    //拾取控制器弹回    [self dismissViewControllerAnimated:YES completion:nil];}/* 取消拍照或录像会调用 */- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker{    NSLog(@"取消");    //拾取控制器弹回    [self dismissViewControllerAnimated:YES completion:nil];}#pragma mark - 保存图片或视频完成的回调- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error                                            contextInfo:(void *)contextInfo {    NSLog(@"保存图片完成");    self.showImageView.image = image;    self.showImageView.contentMode = UIViewContentModeScaleToFill;}- (void)video:(NSString *)videoPath didFinishSavingWithError:(NSError *)error                                                 contextInfo:(void *)contextInfo {    NSLog(@"保存视频完成");}@end

功能十分强大，基本满足一般的需求，使用起来也很简单。

三、AVFoundation的拍照录像

首先了解下AVFoundation做拍照和录像的相关类：

1. AVCaptureSession：
   媒体捕捉会话，负责把捕获到的音视频数据输出到输出设备上，一个会话可以有多个输入输出。
2. AVCaptureVideoPervieewLayer：
   相机拍摄预览图层，是CALayer的子类，实时查看拍照或录像效果。
   
   
   
3. AVCaptureDevice：
   输入设备，包括麦克风、摄像头等，可以设置一些物理设备的属性
4. AVCaptureDeviceInput：
   设备输入数据管理对象，管理输入数据
5. AVCaptureOutput：
   设备输出数据管理对象，管理输出数据，通常使用它的子类：

   AVCaptureAudioDataOutput//输出音频管理对象，输出数据为NSDataAVCaptureStillImageDataOutput//输出图片管理对象，输出数据为NSDataAVCaptureVideoDataOutput//输出视频管理对象，输出数据为NSData/* 输出文件管理对象，输出数据以文件形式输出 */AVCaptureFileOutput  {//子类         AVCaptureAudioFileOutput   //输出是音频文件     AVCaptureMovieFileOutput   //输出是视频文件}

   
   

拍照或录像的一般步骤为：

1. 创建AVCaptureSession对象
2. 使用AVCaptureDevice的类方法获得要使用的设备
3. 利用输入设备AVCaptureDevice创建并初始化AVCaptureDeviceInput对象
4. 初始化输出数据管理对象，看具体输出什么数据决定使用哪个AVCaptureOutput子类
5. 将AVCaptureDeviceInput、AVCaptureOutput添加到媒体会话管理对象AVCaptureSession中
6. 创建视频预览图层AVCaptureVideoPreviewLayer并指定媒体会话，添加图层到显示容器中
7. 调用媒体会话AVCaptureSession的startRunning方法开始捕获，stopRunning方法停止捕捉
8. 将 捕获的音频或视频数据输出到指定文件

拍照使用实例如下：

#import "ViewController.h"#import <AVFoundation/AVFoundation.h>@interface ViewController ()@property (strong, nonatomic) AVCaptureSession *session;//媒体管理会话@property (strong, nonatomic) AVCaptureDeviceInput *captureInput;//输入数据对象@property (strong, nonatomic) AVCaptureStillImageOutput *imageOutput;//输出数据对象@property (strong, nonatomic) AVCaptureVideoPreviewLayer *captureLayer;//视频预览图层@property (strong, nonatomic) IBOutlet UIButton *captureBtn;//拍照按钮@property (strong, nonatomic) IBOutlet UIButton *openCaptureBtn;//打开摄像头按钮@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    [self initCapture];    self.openCaptureBtn.hidden = NO;    self.captureBtn.hidden = YES;}/* 初始化摄像头 */- (void)initCapture{    //1. 创建媒体管理会话    AVCaptureSession *session = [[AVCaptureSession alloc] init];    self.session = session;    //判断分辨率是否支持1280*720，支持就设置为1280*720    if( [session canSetSessionPreset:AVCaptureSessionPreset1280x720] ) {        session.sessionPreset = AVCaptureSessionPreset1280x720;    }    //2. 获取后置摄像头设备对象    AVCaptureDevice *device = nil;    NSArray *cameras = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];    for (AVCaptureDevice *camera in cameras) {        if (camera.position == AVCaptureDevicePositionBack) {//取得后置摄像头            device = camera;        }    }    if(!device) {        NSLog(@"取得后置摄像头错误");        return;    }    //3. 创建输入数据对象    NSError *error = nil;    AVCaptureDeviceInput *captureInput = [[AVCaptureDeviceInput alloc] initWithDevice:device                                                                                error:&error];    if (error) {        NSLog(@"创建输入数据对象错误");        return;    }    self.captureInput = captureInput;    //4. 创建输出数据对象    AVCaptureStillImageOutput *imageOutput = [[AVCaptureStillImageOutput alloc] init];    NSDictionary *setting = @{ AVVideoCodecKey:AVVideoCodecJPEG };    [imageOutput setOutputSettings:setting];    self.imageOutput = imageOutput;    //5. 添加输入数据对象和输出对象到会话中    if ([session canAddInput:captureInput]) {        [session addInput:captureInput];    }    if ([session canAddOutput:imageOutput]) {        [session addOutput:imageOutput];    }    //6. 创建视频预览图层    AVCaptureVideoPreviewLayer *videoLayer =               [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];    self.view.layer.masksToBounds = YES;    videoLayer.frame = self.view.bounds;    videoLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;    //插入图层在拍照按钮的下方    [self.view.layer insertSublayer:videoLayer below:self.captureBtn.layer];    self.captureLayer = videoLayer;}#pragma mark - UI点击/* 点击拍照按钮 */- (IBAction)takeCapture:(id)sender {    //根据设备输出获得连接    AVCaptureConnection *connection = [self.imageOutput connectionWithMediaType:AVMediaTypeVideo];    //通过连接获得设备输出的数据    [self.imageOutput captureStillImageAsynchronouslyFromConnection:connection                      completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error)    {        //获取输出的JPG图片数据        NSData *imageData =               [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];        UIImage *image = [UIImage imageWithData:imageData];        UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);//保存到相册        self.captureLayer.hidden = YES;        self.captureBtn.hidden = YES;        self.openCaptureBtn.hidden = NO;        [self.session stopRunning];//停止捕捉    }];}/* 点击打开摄像头按钮 */- (IBAction)openCapture:(id)sender {    self.captureLayer.hidden = NO;    self.captureBtn.hidden = NO;    self.openCaptureBtn.hidden = YES;    [self.session startRunning];//开始捕捉}@end

录像的操作差不多，下面代码是以上面代码为基础进行修改：

1. 比拍照多了一个音频输入，改变输出数据对象的类
2. 需要处理视频输出代理方法
3. 录制的方法是在输出数据对象上

1. 获取音频输入数据对象以及视频输出数据对象

//获取麦克风设备对象AVCaptureDevice *device = [AVCaptureDevice devicesWithMediaType:AVMediaTypeAudio].firstObject;if(!device) {    NSLog(@"取得麦克风错误");    return;}//创建输入数据对象NSError *error = nil;AVCaptureDeviceInput *audioInput = [[AVCaptureDeviceInput alloc] initWithDevice:device                                                                          error:&error];if (error) {    NSLog(@"创建输入数据对象错误");    return;}//创建视频文件输出对象AVCaptureMovieFileOutput *movieOutput = [[AVCaptureMovieFileOutput alloc] init];self.movieOutput = movieOutput;

2. 添加进媒体管理会话中

if([session canAddInput:captureInput]) {    [session addInput:captureInput];    [session addInput:audioInput];    //添加防抖动功能    AVCaptureConnection *connection = [movieOutput connectionWithMediaType:AVMediaTypeVideo];    if ([connection isVideoStabilizationSupported]) {        connection.preferredVideoStabilizationMode = AVCaptureVideoStabilizationModeAuto;    }}if ([session canAddOutput:movieOutput]) {    [session addOutput:movieOutput];}

3. 点击录像按钮

if (!self.movieOutput.isRecording) {    NSString *outputPath = [NSTemporaryDirectory() stringByAppendingString:@"myMovie.mov"];    NSURL *url = [NSURL fileURLWithPath:outputPath];//记住是文件URL，不是普通URL    //开始录制并设置代理监控录制过程，录制文件会存放到指定URL路径下    [self.movieOutput startRecordingToOutputFileURL:url recordingDelegate:self];} else {    [self.movieOutput stopRecording];//结束录制}

4. 处理录制代理AVCaptureFileOutputRecordingDelegate

/* 开始录制会调用 */- (void)captureOutput:(AVCaptureFileOutput *)captureOutput        didStartRecordingToOutputFileAtURL:(NSURL *)fileURL                           fromConnections:(NSArray *)connections{    NSLog(@"开始录制");}/* 录制完成会调用 */- (void)captureOutput:(AVCaptureFileOutput *)captureOutput        didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL                            fromConnections:(NSArray *)connections                                      error:(NSError *)error{    NSLog(@"完成录制");    NSString *path = outputFileURL.path;    //保存录制视频到相簿    if (UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(path)) {        UISaveVideoAtPathToSavedPhotosAlbum(path, nil, nil, nil);    }}

四、iOS音频视频使用总结

以上的表格中，我没有全部都讲，我主要讲AVFoundation框架，里面还有非常多的内容可以学习，这个框架是非常强大，有时间也可以再深入去学习。