AVFoundation-拍照和录像

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使用AV Foundation 捕捉照片和视频

使用AVFoundation拍照和录制视频的一般步骤如下：

  1. 创建AVCaptureSession对象。
  2. 使用AVCaptureDevice的静态方法获得需要使用的设备，例如拍照和录像就需要获得摄像头设备，录音就要获得麦克风设备。
  3. 利用输入设备AVCaptureDevice初始化AVCaptureDeviceInput对象。
  4. 初始化输出数据管理对象，如果要拍照就初始化AVCaptureStillImageOutput对象；如果拍摄视频就初始化AVCaptureMovieFileOutput对象。
  5. 将数据输入对象AVCaptureDeviceInput、数据输出对象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，调用AVCaptureSession的startRuning方法开始捕获。
  7. 将捕获的音频或视频数据输出到指定文件。

主要用到的类：

  • AVCaptureDeviceInput (输入设备)
    • AVCaptureDevice
  • AVCaptureSession （捕捉会话）
  • AVCaptureVideoPreviewLayer （展示层)
  • AVCaptureOutput （输出）
    • AVCaptureStillImageOutput (捕捉图片)
    • AVCaptureAudioDataOutput
    • AVCaptureVideoDataOutput
    • AVCaptureFileOutput

配置会话：

简单配置会话

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//初始化会话
    _captureSession=[[AVCaptureSession alloc]init];
    if ([_captureSession canSetSessionPreset:AVCaptureSessionPreset1280x720]) {//设置分辨率
        _captureSession.sessionPreset=AVCaptureSessionPreset1280x720;
        //_captureSession.sessionPreset=AVCaptureSessionPresetHigh;
    }
    //获得视频捕捉设备
    AVCaptureDevice *captureDevice=[self getCameraDeviceWithPosition:AVCaptureDevicePositionBack];//取得后置摄像头
    //	AVCaptureDevice *videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];//获取默认摄像头
    if (!captureDevice) {
        NSLog(@"取得后置摄像头时出现问题.");
        return;
    }
        
    NSError *error=nil;
    //根据输入设备初始化设备输入对象，用于获得输入数据
    _captureDeviceInput=[[AVCaptureDeviceInput alloc]initWithDevice:captureDevice error:&error];
    if (error) {
        NSLog(@"取得设备输入对象时出错，错误原因：%@",error.localizedDescription);
        return;
    }
    
    
   
    //获取静态图片输出
    _captureStillImageOutput=[[AVCaptureStillImageOutput alloc]init];
    NSDictionary *outputSettings = @{AVVideoCodecKey:AVVideoCodecJPEG};
    [_captureStillImageOutput setOutputSettings:outputSettings];//输出设置
    
    //将设备输入添加到会话中
    if ([_captureSession canAddInput:_captureDeviceInput]) {
        [_captureSession addInput:_captureDeviceInput];
    }
    
    //将设备输出添加到会话中
    if ([_captureSession canAddOutput:_captureStillImageOutput]) {
        [_captureSession addOutput:_captureStillImageOutput];
    }
    
    //创建视频预览层，用于实时展示摄像头状态
    _captureVideoPreviewLayer=[[AVCaptureVideoPreviewLayer alloc]initWithSession:self.captureSession];
    
    CALayer *layer=self.viewContainer.layer;
    layer.masksToBounds=YES;
    
    _captureVideoPreviewLayer.frame=layer.bounds;
    _captureVideoPreviewLayer.videoGravity=AVLayerVideoGravityResizeAspectFill;//填充模式
    //将视频预览层添加到界面中
    \[layer addSublayer:_captureVideoPreviewLayer];

添加音频捕捉设备（麦克风）

输入不仅可以添加摄像头 ，页可以添加麦克风

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// Setup default microphone
AVCaptureDevice *audioDevice =                                          // 5
    [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];

AVCaptureDeviceInput *audioInput =                                      // 6
    [AVCaptureDeviceInput deviceInputWithDevice:audioDevice error:error];
if (audioInput) {
    if ([self.captureSession canAddInput:audioInput]) {                 // 7
        [self.captureSession addInput:audioInput];
    }
} else {
    return NO;
}

添加视频输出

输出不仅可以添加静态图片，可以添加视频输出

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// Setup movie file output
self.movieOutput = [[AVCaptureMovieFileOutput alloc] init];             // 9

if ([self.captureSession canAddOutput:self.movieOutput]) {
    [self.captureSession addOutput:self.movieOutput];
}

启动或者停止会话

启动会话，使它处于图片和视频捕捉状态。最好不要在主线程中启动。

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- (void)startSession {
	if (![self.captureSession isRunning]) {                                 // 1
		dispatch_async([self globalQueue], ^{
			[self.captureSession startRunning];
		});
	}
}

- (void)stopSession {
	if ([self.captureSession isRunning]) {                                  // 2
		dispatch_async([self globalQueue], ^{
			[self.captureSession stopRunning];
		});
	}
}

隐私访问权限

xcode8 iOS10中后不添加权限会出错

在info.plist文件添加对应的Key-Value:

聚焦(自动聚焦，手动聚焦)

坐标空间转换

如iPhone5屏幕坐标系左上角为（0，0）垂直时右下角为（320，568），水平时右下角（568，320）。
而设备坐标系基于摄像头的本地设置，左上角为（0，0）右下角为（1，1）。

AVCaptureVideoPreviewLayer定义了两个方法用于转换两者间的坐标：

  • - (CGPoint)captureDevicePointOfInterestForPoint:(CGPoint)pointInLayer NS_AVAILABLE_IOS(6_0);
    • 将屏幕坐标系转换为设备坐标系
  • - (CGPoint)pointForCaptureDevicePointOfInterest:(CGPoint)captureDevicePointOfInterest NS_AVAILABLE_IOS(6_0);
    • 将设备坐标系转换为屏幕坐标系

设置对焦模式

对焦模式AVCaptureFlashMode有 三种 AVCaptureFlashModeOff 、AVCaptureFlashModeOn 和 AVCaptureFlashModeAuto
配置设备时一定要判断一下设备是否支持，比如前置摄像头不支持对焦操作
修改设备配置时需要先锁定配置 lockForConfiguration 执行所需的修改，最后解锁设备 unlockForConfiguration 

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- (void)setFlashMode:(AVCaptureFlashMode)flashMode {

    AVCaptureDevice *device = [self activeCamera];

    if (device.flashMode != flashMode &&
        [device isFlashModeSupported:flashMode]) {

        NSError *error;
        if ([device lockForConfiguration:&error]) {
            device.flashMode = flashMode;
            [device unlockForConfiguration];
        } else {
            [self.delegate deviceConfigurationFailedWithError:error];
        }
    }
}

点击对焦

将屏幕坐标转换为捕捉设备坐标，然后将 focusPointOfInterest 设置为该坐标

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#pragma mark - Focus Methods

- (BOOL)cameraSupportsTapToFocus {                                          // 1
    return [[self activeCamera] isFocusPointOfInterestSupported];
}

- (void)focusAtPoint:(CGPoint)point {                                       // 2

    AVCaptureDevice *device = [self activeCamera];

    if (device.isFocusPointOfInterestSupported &&                           // 3
        [device isFocusModeSupported:AVCaptureFocusModeAutoFocus]) {

        NSError *error;
        if ([device lockForConfiguration:&error]) {                         // 4
            device.focusPointOfInterest = point;
            device.focusMode = AVCaptureFocusModeAutoFocus;
            [device unlockForConfiguration];
        } else {
            [self.delegate deviceConfigurationFailedWithError:error];
        }
    }
}

调整曝光模式

与调整对焦模式类似，可以调整曝光模式 device.exposureMode
AVCaptureExposureModeLocked 锁定曝光 AVCaptureExposureModeAutoExpose 自动曝光 AVCaptureExposureModeContinuousAutoExposure 自动持续曝光 AVCaptureExposureModeCustom 自定义曝光 四个值

调整闪光灯模式

与之前的两个类似

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- (BOOL)cameraHasTorch {
    return [[self activeCamera] hasTorch];
}

- (AVCaptureTorchMode)torchMode {
    return [[self activeCamera] torchMode];
}

- (void)setTorchMode:(AVCaptureTorchMode)torchMode {

    AVCaptureDevice *device = [self activeCamera];

    if (device.torchMode != torchMode &&
        [device isTorchModeSupported:torchMode]) {

        NSError *error;
        if ([device lockForConfiguration:&error]) {
            device.torchMode = torchMode;
            [device unlockForConfiguration];
        } else {
            [self.delegate deviceConfigurationFailedWithError:error];
        }
    }
}

切换摄像头

切换摄像头时担心停止会话和重启会话带来的开销，但是对会话进行改变时，要通过 beginConfiguration 和 commitConfiguration 进行单独的原子性的变化。

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#pragma mark - Device Configuration

//返回指定位置的AVCaptureDevice **AVCaptureDevicePositionBack** 和 **AVCaptureDevicePositionFront**
- (AVCaptureDevice *)cameraWithPosition:(AVCaptureDevicePosition)position { // 1
	NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
	for (AVCaptureDevice *device in devices) {                              // 2
		if (device.position == position) {
			return device;
		}
	}
	return nil;
}
//当前捕捉会话对应的摄像头
- (AVCaptureDevice *)activeCamera {                                         // 3
    return self.activeVideoInput.device;
}
//当前为激活的摄像头
- (AVCaptureDevice *)inactiveCamera {                                       // 4
    AVCaptureDevice *device = nil;
    if (self.cameraCount > 1) {
        if ([self activeCamera].position == AVCaptureDevicePositionBack) {  // 5
            device = [self cameraWithPosition:AVCaptureDevicePositionFront];
        } else {
            device = [self cameraWithPosition:AVCaptureDevicePositionBack];
        }
    }
    return device;
}
//是否超过一个摄像头可用
- (BOOL)canSwitchCameras {                                                  // 6
    return self.cameraCount > 1;
}
//可用的视频捕捉设备的数量
- (NSUInteger)cameraCount {                                                 // 7
    return [[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo] count];
}

- (BOOL)switchCameras {

    if (![self canSwitchCameras]) {                                         // 1
        return NO;
    }

    NSError *error;
    AVCaptureDevice *videoDevice = [self inactiveCamera];                   // 2

    AVCaptureDeviceInput *videoInput =
    [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error];

    if (videoInput) {
        [self.captureSession beginConfiguration];                           // 3

        [self.captureSession removeInput:self.activeVideoInput];            // 4
       
        if ([self.captureSession canAddInput:videoInput]) {                 // 5
            [self.captureSession addInput:videoInput];
            self.activeVideoInput = videoInput;
        } else {//若不能添加新输入则重新添加之前的输入
            [self.captureSession addInput:self.activeVideoInput];
        }

        [self.captureSession commitConfiguration];                          // 6

    } else {
        [self.delegate deviceConfigurationFailedWithError:error];           // 7
        return NO;
    }

    return YES;
}


拍照，获取静态图片

AVCaptureStillImageOutput 用于捕捉静态图片，执行- (void)captureStillImageAsynchronouslyFromConnection:(AVCaptureConnection *)connection completionHandler:(void (^)(CMSampleBufferRef imageDataSampleBuffer, NSError *error))handler;方法来获取图片
使用 ALAssetsLibrary来将图片储存在照片中

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//拍照
- (void)captureStillImage {

    AVCaptureConnection *connection =                                   
        [self.imageOutput connectionWithMediaType:AVMediaTypeVideo];

    if (connection.isVideoOrientationSupported) {                       
        connection.videoOrientation = [self currentVideoOrientation];
    }

    id handler = ^(CMSampleBufferRef sampleBuffer, NSError *error) {
        if (sampleBuffer != NULL) {

            NSData *imageData =
                [AVCaptureStillImageOutput
                    jpegStillImageNSDataRepresentation:sampleBuffer];

            UIImage *image = [[UIImage alloc] initWithData:imageData];
            [self writeImageToAssetsLibrary:image];                         // 1

        } else {
            NSLog(@"NULL sampleBuffer: %@", [error localizedDescription]);
        }
    };
    // Capture still image
    [self.imageOutput captureStillImageAsynchronouslyFromConnection:connection
                                                  completionHandler:handler];
}
//保存在本地照片
- (void)writeImageToAssetsLibrary:(UIImage *)image {

    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];              // 2

    [library writeImageToSavedPhotosAlbum:image.CGImage                     // 3
                              orientation:(NSInteger)image.imageOrientation // 4
                          completionBlock:^(NSURL *assetURL, NSError *error) {
                              if (!error) {
                                  [self postThumbnailNotifification:image]; // 5
                              } else {
                                  id message = [error localizedDescription];
                                  NSLog(@"Error: %@", message);
                              }
                          }];
}

- (void)postThumbnailNotifification:(UIImage *)image {
    dispatch_async(dispatch_get_main_queue(), ^{
        NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
        [nc postNotificationName:THThumbnailCreatedNotification object:image];
    });
}

视频捕捉

使用AVCaptureMovieFileOutput 来捕捉视频
在录制开始时，在文件的最前面会写入一个最小化的头信息，随着录制的进行，片段按照一定周期写入，创建完整的头信息，这样就确保了当程序遇到崩溃或者中断时，影片仍然会以最后一个写入的片段为重点进行保存。

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#pragma mark - Video Capture Methods

- (BOOL)isRecording {                                                       // 1
    return self.movieOutput.isRecording;
}
//获取处理当前视频捕捉连接的信息，对捕捉的视频数据配置一些核心属性
- (void)startRecording {

    if (![self isRecording]) {

		AVCaptureConnection *videoConnection =                              // 2
            [self.movieOutput connectionWithMediaType:AVMediaTypeVideo];
        //视频方向
		if ([videoConnection isVideoOrientationSupported]) {                // 3
			videoConnection.videoOrientation = self.currentVideoOrientation;
		}
        //支持视频稳定
		if ([videoConnection isVideoStabilizationSupported]) {              // 4
            
            if ([[[UIDevice currentDevice] systemVersion] floatValue] < 8.0) {
                videoConnection.enablesVideoStabilizationWhenAvailable = YES;
            } else {
                videoConnection.preferredVideoStabilizationMode = AVCaptureVideoStabilizationModeAuto;
            }
		}

        AVCaptureDevice *device = [self activeCamera];
        //支持平滑对焦，即减慢摄像头镜头对焦的速度
        if (device.isSmoothAutoFocusSupported) {                            // 5
            NSError *error;
            if ([device lockForConfiguration:&error]) {
                device.smoothAutoFocusEnabled = NO;
                [device unlockForConfiguration];
            } else {
                [self.delegate deviceConfigurationFailedWithError:error];
            }
        }

        self.outputURL = [self uniqueURL];                                  // 6
        //开始录制
		[self.movieOutput startRecordingToOutputFileURL:self.outputURL      // 8
                                      recordingDelegate:self];

    }
}

- (CMTime)recordedDuration {
    return self.movieOutput.recordedDuration;
}
//视频文件写入目录
- (NSURL *)uniqueURL {                                                      // 7

    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSString *dirPath =
        [fileManager temporaryDirectoryWithTemplateString:@"kamera.XXXXXX"];

    if (dirPath) {
        NSString *filePath =
            [dirPath stringByAppendingPathComponent:@"kamera_movie.mov"];
        return [NSURL fileURLWithPath:filePath];
    }

    return nil;
}

- (void)stopRecording {                                                     // 9
    if ([self isRecording]) {
        [self.movieOutput stopRecording];
    }
}

#pragma mark - AVCaptureFileOutputRecordingDelegate
//在AVCaptureFileOutputRecordingDelegate 实现中获取最终文件并写入
- (void)captureOutput:(AVCaptureFileOutput *)captureOutput
didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL
      fromConnections:(NSArray *)connections
                error:(NSError *)error {
	if (error) {                                                            // 1
        [self.delegate mediaCaptureFailedWithError:error];
	} else {
        [self writeVideoToAssetsLibrary:[self.outputURL copy]];
	}
    self.outputURL = nil;
}

- (void)writeVideoToAssetsLibrary:(NSURL *)videoURL {

    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];              // 2

    if ([library videoAtPathIsCompatibleWithSavedPhotosAlbum:videoURL]) {   // 3

        ALAssetsLibraryWriteVideoCompletionBlock completionBlock;

        completionBlock = ^(NSURL *assetURL, NSError *error){               // 4
            if (error) {
                [self.delegate assetLibraryWriteFailedWithError:error];
            } else {
                [self generateThumbnailForVideoAtURL:videoURL];
            }
        };

        [library writeVideoAtPathToSavedPhotosAlbum:videoURL                // 8
                                    completionBlock:completionBlock];
    }
}
//视频缩略图
- (void)generateThumbnailForVideoAtURL:(NSURL *)videoURL {

    dispatch_async([self globalQueue], ^{

        AVAsset *asset = [AVAsset assetWithURL:videoURL];

        AVAssetImageGenerator *imageGenerator =                             // 5
            [AVAssetImageGenerator assetImageGeneratorWithAsset:asset];
        imageGenerator.maximumSize = CGSizeMake(100.0f, 0.0f);
        imageGenerator.appliesPreferredTrackTransform = YES;

        CGImageRef imageRef = [imageGenerator copyCGImageAtTime:kCMTimeZero // 6
                                                     actualTime:NULL
                                                          error:nil];
        UIImage *image = [UIImage imageWithCGImage:imageRef];
        CGImageRelease(imageRef);

        dispatch_async(dispatch_get_main_queue(), ^{                        // 7
            [self postThumbnailNotifification:image];
        });
    });
}

#pragma mark - Recoding Destination URL

- (AVCaptureVideoOrientation)currentVideoOrientation {

    AVCaptureVideoOrientation orientation;

    switch ([UIDevice currentDevice].orientation) {                         // 3
        case UIDeviceOrientationPortrait:
            orientation = AVCaptureVideoOrientationPortrait;
            break;
        case UIDeviceOrientationLandscapeRight:
            orientation = AVCaptureVideoOrientationLandscapeLeft;
            break;
        case UIDeviceOrientationPortraitUpsideDown:
            orientation = AVCaptureVideoOrientationPortraitUpsideDown;
            break;
        default:
            orientation = AVCaptureVideoOrientationLandscapeRight;
            break;
    }

    return orientation;
}