AVFoundation 媒体捕捉（1）

图片视频捕捉功能

AVFoundation

捕捉会话：AVCaptureSession
捕捉设备：AVCaptureDevice
捕捉设备输入：AVCaptureDeviceInput
捕捉设备输出：AVCaptureOutput抽象类
AVCaptureStillImageOutput
AVCaputureMovieFileOutput
AVCaputureAudioDataOutput
AVCaputureVideoDataOutput
捕捉连接：AVCaptureConnection
捕捉预览：AVCaptureVideoPreviewLayer

用法实例：

目的：视频/照片的捕捉

设置session
初始化
配置分配率
配置输入设备(注意转换为AVCaptureDeviceInput)
配置输入设备包括音频输入，视频输入
配置输出(静态图片输出，视频文件输出)
在为session添加输入输出时，注意一定判断是否能添加：原因是：摄像头并不隶属于任何一个APP，它是公共设备。

实例代码

- (BOOL)setupSession:(NSError **)error {
    //创建捕捉会话。AVCaptureSession 是捕捉场景的中心枢纽
    self.captureSession = [[AVCaptureSession alloc]init];
    /*
     AVCaptureSessionPresetHigh
     AVCaptureSessionPresetMedium
     AVCaptureSessionPresetLow
     AVCaptureSessionPreset640x480
     AVCaptureSessionPreset1280x720
     AVCaptureSessionPresetPhoto
     */
    //设置图像的分辨率
    self.captureSession.sessionPreset = AVCaptureSessionPresetHigh;
    
    //拿到默认视频捕捉设备 iOS系统返回后置摄像头
    AVCaptureDevice *videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    
    //将捕捉设备封装成AVCaptureDeviceInput
    //注意：为会话添加捕捉设备，必须将设备封装成AVCaptureDeviceInput对象
    AVCaptureDeviceInput *videoInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:error];
    
    //判断videoInput是否有效
    if (videoInput){
        //canAddInput：测试是否能被添加到会话中
        if ([self.captureSession canAddInput:videoInput]){
            //将videoInput 添加到 captureSession中
            [self.captureSession addInput:videoInput];
            self.activeVideoInput = videoInput;
        }
    }else{
        return NO;
    }
    
    //选择默认音频捕捉设备 即返回一个内置麦克风
    AVCaptureDevice *audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
    
    //为这个设备创建一个捕捉设备输入
    AVCaptureDeviceInput *audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioDevice error:error];
   
    //判断audioInput是否有效
    if (audioInput) {
        
        //canAddInput：测试是否能被添加到会话中
        if ([self.captureSession canAddInput:audioInput])
        {
            //将audioInput 添加到 captureSession中
            [self.captureSession addInput:audioInput];
        }
    }else
    {
        return NO;
    }

    //AVCaptureStillImageOutput 实例 从摄像头捕捉静态图片
    self.imageOutput = [[AVCapturePhotoOutput alloc]init];
    //配置字典：希望捕捉到JPEG格式的图片
//    self.imageOutput.outputSettings = @{AVVideoCodecKey:AVVideoCodecTypeJPEG};
    //输出连接 判断是否可用，可用则添加到输出连接中去
    if ([self.captureSession canAddOutput:self.imageOutput])
    {
        [self.captureSession addOutput:self.imageOutput];
    }
    //创建一个AVCaptureMovieFileOutput 实例，用于将Quick Time 电影录制到文件系统
    self.movieOutput = [[AVCaptureMovieFileOutput alloc]init];
    //输出连接 判断是否可用，可用则添加到输出连接中去
    if ([self.captureSession canAddOutput:self.movieOutput])
    {
        [self.captureSession addOutput:self.movieOutput];
    }
    return YES;
}

如此捕捉已经完成，接下来看预览

捕捉预览

1）在UIView 重写layerClass 类方法可以让开发者创建视图实例自定义图层了下
重写layerClass方法并返回AVCaptureVideoPrevieLayer类对象

@interface THPreviewView : UIView
//session用来关联AVCaptureVideoPreviewLayer 和 激活AVCaptureSession
@property (strong, nonatomic) AVCaptureSession *session;
@end

@implementation THPreviewView

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        [self setupView];
    }
    return self;
}

- (void)setupView {
    [(AVCaptureVideoPreviewLayer *)self.layer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
}

+ (Class)layerClass {
    //在UIView 重写layerClass 类方法可以让开发者创建视图实例自定义图层了下
    //重写layerClass方法并返回AVCaptureVideoPrevieLayer类对象
    return [AVCaptureVideoPreviewLayer class];
}

- (AVCaptureSession*)session {
    //重写session方法，返回捕捉会话
    return [(AVCaptureVideoPreviewLayer*)self.layer session];
}

- (void)setSession:(AVCaptureSession *)session {
    //重写session属性的访问方法，在setSession:方法中访问视图layer属性。
    //AVCaptureVideoPreviewLayer 实例，并且设置AVCaptureSession 将捕捉数据直接输出到图层中，并确保与会话状态同步。
    [(AVCaptureVideoPreviewLayer*)self.layer setSession:session];
}

捕捉预览

如此就完成了捕捉及预览了

@implementation ViewController

    [self setupSession: nil];
    self.previewView = [THPreviewView new];
    self.previewView.frame = self.view.bounds;
    self.previewView.session = self.captureSession;
    [self.view addSubview:self.previewView];
    [self.captureSession startRunning];

其他功能

调换摄像头

//切换摄像头
- (BOOL)switchCameras {
    //判断是否有多个摄像头
    if (![self canSwitchCameras]){
        return NO;
    }
    //获取当前设备的反向设备
    NSError *error;
    AVCaptureDevice *videoDevice = [self inactiveCamera];
    
    //将输入设备封装成AVCaptureDeviceInput
    AVCaptureDeviceInput *videoInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error];
    //判断videoInput 是否为nil
    if (videoInput){
        //标注原配置变化开始
        [self.captureSession beginConfiguration];
        //将捕捉会话中，原本的捕捉输入设备移除
        [self.captureSession removeInput:self.activeVideoInput];
        //判断新的设备是否能加入
        if ([self.captureSession canAddInput:videoInput]){
            //能加入成功，则将videoInput 作为新的视频捕捉设备
            [self.captureSession addInput:videoInput];
            //将获得设备 改为 videoInput
            self.activeVideoInput = videoInput;
        }else{
            //如果新设备，无法加入。则将原本的视频捕捉设备重新加入到捕捉会话中
            [self.captureSession addInput:self.activeVideoInput];
        }
        //配置完成后， AVCaptureSession commitConfiguration 会分批的将所有变更整合在一起。
        [self.captureSession commitConfiguration];
    } else{
        //创建AVCaptureDeviceInput 出现错误，则通知委托来处理该错误
//        [self.delegate deviceConfigurationFailedWithError:error];
        return NO;
    }
    return YES;
}


//判断是否有超过1个摄像头可用
- (BOOL)canSwitchCameras {
    return self.cameraCount > 1;
}

//可用视频捕捉设备的数量
- (NSUInteger)cameraCount {
     return [[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo] count];
}

- (AVCaptureDevice *)activeCamera {
    //返回当前捕捉会话对应的摄像头的device 属性
    return self.activeVideoInput.device;
}

//返回当前未激活的摄像头
- (AVCaptureDevice *)inactiveCamera {
    //通过查找当前激活摄像头的反向摄像头获得，如果设备只有1个摄像头，则返回nil
       AVCaptureDevice *device = nil;
      if (self.cameraCount > 1){
          if ([self activeCamera].position == AVCaptureDevicePositionBack) {
               device = [self cameraWithPosition:AVCaptureDevicePositionFront];
         }else{
             device = [self cameraWithPosition:AVCaptureDevicePositionBack];
         }
     }
    return device;
}

- (AVCaptureDevice *)cameraWithPosition:(AVCaptureDevicePosition)position {
    //获取可用视频设备
    NSArray *devicess = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    //遍历可用的视频设备 并返回position 参数值
    for (AVCaptureDevice *device in devicess){
        if (device.position == position) {
            return device;
        }
    }
    return nil;
}

然后调用 switchCameras就能调换摄像头了

摄像头聚焦

- (void)focusAtPoint:(CGPoint)point {
    AVCaptureDevice *device = [self activeCamera];
        //是否支持兴趣点对焦 & 是否自动对焦模式
    if (device.isFocusPointOfInterestSupported && [device isFocusModeSupported:AVCaptureFocusModeAutoFocus]) {
        NSError *error;
        //锁定设备准备配置，如果获得了锁
        if ([device lockForConfiguration:&error]) {
            //将focusPointOfInterest属性设置CGPoint
            device.focusPointOfInterest = point;
            //focusMode 设置为AVCaptureFocusModeAutoFocus
            device.focusMode = AVCaptureFocusModeAutoFocus;
            //释放该锁定
            [device unlockForConfiguration];
        }else{
            //错误时，则返回给错误处理代理
        }
    }
}

曝光

static const NSString *THCameraAdjustingExposureContext;

(void)exposeAtPoint:(CGPoint)point {
AVCaptureDevice *device = [self activeCamera];
AVCaptureExposureMode exposureMode =AVCaptureExposureModeContinuousAutoExposure;
//判断是否支持 AVCaptureExposureModeContinuousAutoExposure 模式
if (device.isExposurePointOfInterestSupported && [device isExposureModeSupported:exposureMode]) {
[device isExposureModeSupported:exposureMode];
NSError *error;
//锁定设备准备配置
if ([device lockForConfiguration:&error]) {
//配置期望值
device.exposurePointOfInterest = point;
device.exposureMode = exposureMode;
//判断设备是否支持锁定曝光的模式。
if ([device isExposureModeSupported:AVCaptureExposureModeLocked]) {
//支持，则使用kvo确定设备的adjustingExposure属性的状态。
[device addObserver:self forKeyPath:@"adjustingExposure" options:NSKeyValueObservingOptionNew context:&THCameraAdjustingExposureContext];
}
//释放该锁定
[device unlockForConfiguration];
}else{
///错误处理
}
}
}

拍摄静态图片

#pragma mark - Image Capture Methods 拍摄静态图片
/*
    AVCaptureStillImageOutput 是AVCaptureOutput的子类。用于捕捉图片
 */
- (void)captureStillImage {
    //获取连接
    AVCaptureConnection *connection = [self.imageOutput connectionWithMediaType:AVMediaTypeVideo];
    //程序只支持纵向，但是如果用户横向拍照时，需要调整结果照片的方向
    //判断是否支持设置视频方向
    if (connection.isVideoOrientationSupported) {
        //获取方向值
        connection.videoOrientation = [self currentVideoOrientation];
    }
    //定义一个handler 块，会返回1个图片的NSData数据
    id handler = ^(CMSampleBufferRef sampleBuffer,NSError *error){
                    if (sampleBuffer != NULL) {
                        NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:sampleBuffer];
                        UIImage *image = [[UIImage alloc]initWithData:imageData];
                        //重点：捕捉图片成功后，将图片传递出去
                        [self writeImageToAssetsLibrary:image];
                    }else{
                        NSLog(@"NULL sampleBuffer:%@",[error localizedDescription]);
                    }
                };
    //捕捉静态图片
    [self.imageOutput captureStillImageAsynchronouslyFromConnection:connection completionHandler:handler];
}

/*
    Assets Library 框架
    用来让开发者通过代码方式访问iOS photo
    注意：会访问到相册，需要修改plist 权限。否则会导致项目崩溃
 */
- (void)writeImageToAssetsLibrary:(UIImage *)image {
    //创建ALAssetsLibrary  实例
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc]init];
    //参数1:图片（参数为CGImageRef 所以image.CGImage）
    //参数2:方向参数 转为NSUInteger
    //参数3:写入成功、失败处理
    [library writeImageToSavedPhotosAlbum:image.CGImage
                             orientation:(NSUInteger)image.imageOrientation
                         completionBlock:^(NSURL *assetURL, NSError *error) {
                         }];
}

//获取方向值
- (AVCaptureVideoOrientation)currentVideoOrientation {
    AVCaptureVideoOrientation orientation;
    //获取UIDevice 的 orientation
    switch ([UIDevice currentDevice].orientation) {
        case UIDeviceOrientationPortrait:
            orientation = AVCaptureVideoOrientationPortrait;
            break;
        case UIDeviceOrientationLandscapeRight:
            orientation = AVCaptureVideoOrientationLandscapeLeft;
            break;
        case UIDeviceOrientationPortraitUpsideDown:
            orientation = AVCaptureVideoOrientationPortraitUpsideDown;
            break;
        default:
            orientation = AVCaptureVideoOrientationLandscapeRight;
            break;
    }
    return orientation;
}

捕捉视频

#pragma mark - Video Capture Methods 捕捉视频
//判断是否录制状态
- (BOOL)isRecording {
    return self.movieOutput.isRecording;
}
//开始录制
- (void)startRecording {
    if (![self isRecording]) {
        //获取当前视频捕捉连接信息，用于捕捉视频数据配置一些核心属性
        AVCaptureConnection * videoConnection = [self.movieOutput connectionWithMediaType:AVMediaTypeVideo];
        //判断是否支持设置videoOrientation 属性。
        if([videoConnection isVideoOrientationSupported]){
            //支持则修改当前视频的方向
            videoConnection.videoOrientation = [self currentVideoOrientation];
        }
        //判断是否支持视频稳定 可以显著提高视频的质量。只会在录制视频文件涉及
        if([videoConnection isVideoStabilizationSupported]){
            videoConnection.enablesVideoStabilizationWhenAvailable = YES;
        }
        AVCaptureDevice *device = [self activeCamera];
        //摄像头可以进行平滑对焦模式操作。即减慢摄像头镜头对焦速度。当用户移动拍摄时摄像头会尝试快速自动对焦。
        if (device.isSmoothAutoFocusEnabled) {
            NSError *error;
            if ([device lockForConfiguration:&error]) {
                device.smoothAutoFocusEnabled = YES;
                [device unlockForConfiguration];
            } else  {
                /// 错误处理
//                [self.delegate deviceConfigurationFailedWithError:error];
            }
        }
        //查找写入捕捉视频的唯一文件系统URL.
        self.outputURL = [self uniqueURL];
        //在捕捉输出上调用方法 参数1:录制保存路径  参数2:代理
        [self.movieOutput startRecordingToOutputFileURL:self.outputURL recordingDelegate:self];
    }
}

//停止录制
- (void)stopRecording {
    //是否正在录制
    if ([self isRecording]) {
        [self.movieOutput stopRecording];
    }
}

//写入视频唯一文件系统URL
- (NSURL *)uniqueURL {
    NSFileManager *fileManager = [NSFileManager defaultManager];
    //temporaryDirectoryWithTemplateString  可以将文件写入的目的创建一个唯一命名的目录；
    NSString *dirPath = [fileManager temporaryDirectoryWithTemplateString:@"kamera.XXXXXX"];
    if (dirPath) {
        NSString *filePath = [dirPath stringByAppendingPathComponent:@"kamera_movie.mov"];
        return  [NSURL fileURLWithPath:filePath];
    }
    return nil;
}

#pragma mark - AVCaptureFileOutputRecordingDelegate

- (void)captureOutput:(AVCaptureFileOutput *)captureOutput
didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL
      fromConnections:(NSArray *)connections
                error:(NSError *)error {
    //错误
    if (error) {
//        [self.delegate mediaCaptureFailedWithError:error];
    }else{
        //写入
        [self writeVideoToAssetsLibrary:[self.outputURL copy]];
    }
    self.outputURL = nil;
}

//写入捕捉到的视频
- (void)writeVideoToAssetsLibrary:(NSURL *)videoURL {
    //ALAssetsLibrary 实例 提供写入视频的接口
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc]init];
    //写资源库写入前，检查视频是否可被写入 （写入前尽量养成判断的习惯）
    if ([library videoAtPathIsCompatibleWithSavedPhotosAlbum:videoURL]) {
        //创建block块
        ALAssetsLibraryWriteVideoCompletionBlock completionBlock;
        completionBlock = ^(NSURL *assetURL,NSError *error){
            if (error) {
//                [self.delegate assetLibraryWriteFailedWithError:error];
            }else{
                //用于界面展示视频缩略图
//                [self generateThumbnailForVideoAtURL:videoURL];
            }
        };
        //执行实际写入资源库的动作
        [library writeVideoAtPathToSavedPhotosAlbum:videoURL completionBlock:completionBlock];
    }
}

demo
kwwh

AVFoundation 媒体捕捉（1）

AVFoundation

用法实例：

实例代码

捕捉预览

捕捉预览

其他功能

调换摄像头

摄像头聚焦

曝光

拍摄静态图片

捕捉视频

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