iOS捕捉圖像

iOS媒體捕捉

一、捕捉類介紹

1. 捕捉會話AVCaptureSession

   AV Foundation捕捉棧的核心類是AVCaptureSession,這個類相當與一個插排，用于連接配接輸入和輸出資源，

   捕捉會話還可以額外配置一個會話預設值（session preset）用來控制捕捉資料的格式和品質

2. 捕捉裝置AVCaptureDevice

   AVCaptureDevice為攝像頭或麥克風等實體裝置定義了一個接口，它針對實體硬體裝置定義了大量的控制

   //根據媒體類型傳回一個系統指定的預設裝置
   AVCaptureDevice *videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
              

3. 捕捉裝置的輸入AVCaptureDeviceInput

   AVCaptureDevice不能之間介入會話，需要借助AVCaptureDeviceInput執行個體來封裝一下

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

4. 捕捉的輸出AVCaptureOutput

   AVCaptureOutput是一個抽象基類，AVFoundation定義了一些這個抽象類的進階拓展類

   • AVCaptureStillImageOutput:靜态圖檔輸出
   • AVCaptureMovieFileOutput:視訊輸出
   • AVCaptureVideoDataOutput:視訊資料輸出
   • AVCaptureAudioDataOutput:音頻資料輸出

5. 捕捉連接配接AVCaptureConnection

   捕捉會話需要确定有給定捕捉裝置輸入渲染的媒體類型，并自動建立其能夠接收該媒體類型的捕捉輸出端的連接配接。

6. 捕捉預覽AVCaptureVideoPreviewLayer

   AVCaptureVideoPreviewLayer可以預覽正在捕捉的畫面

二、建立捕捉

建立捕捉的步驟

• 建立一個一個AVCaptureSession
• 擷取一個AVCaptureDevice
• 為AVCaptureDevice建立一個AVCaptureDeviceInput
• 将AVCaptureDeviceInput添加到AVCaptureSession
• 建立一個AVCaptureDeviceOutPut
• 将AVCaptureDeviceOutPut添加到AVCaptureSession
• AVCaptureSession開始捕捉
  1. 配置會話

  - (BOOL)setupSession {
  
   //設定session
   self.session = [[AVCaptureSession alloc] init];
   if([self.session canSetSessionPreset:AVCaptureSessionPresetMedium]){
       self.session.sessionPreset = AVCaptureSessionPresetMedium;
   }
  
   //設定視訊輸入裝置
   _videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
   _videoDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:_videoDevice error:nil];
   if(_videoDeviceInput){
       if([self.session canAddInput:_videoDeviceInput]){
           [self.session addInput:_videoDeviceInput];
       }
   }else{
       return NO;
   }
  
   //設定音頻輸入裝置
   _audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
   _audioDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:_audioDevice error:nil];
   if(_audioDeviceInput){
       if([self.session canAddInput:_audioDeviceInput]){
           [self.session addInput:_audioDeviceInput];
       }
   }else{
       return NO;
   }
  
   //設定視訊資料輸出
   _videoDataOutPut = [[AVCaptureMovieFileOutput alloc] init];
   if([self.session canAddOutput:_videoDataOutPut]){
       [self.session addOutput:_videoDataOutPut];
   }
  
   //設定圖檔輸出
   _stillImageOutPut = [[AVCaptureStillImageOutput alloc] init];
   _stillImageOutPut.outputSettings = @{AVVideoCodecKey:AVVideoCodecJPEG};
   if([self.session canAddOutput:_stillImageOutPut]){
       [self.session addOutput:_stillImageOutPut];
   }
  
   //運作線程
   _vidoQueue = dispatch_queue_create("Sun.VideoQueue", DISPATCH_QUEUE_SERIAL);
  
   return YES;
  }
             

  1. 開始停止捕捉

  - (void)startSession {
   if(self.session.isRunning == NO){
       dispatch_async(_vidoQueue, ^{
           [self.session startRunning];
       });
   }
  }
  
  - (void)stopSession {
   if(self.session.isRunning == YES){
       dispatch_async(_vidoQueue, ^{
           [self.session stopRunning];
       });
   }
  }
             

  1. 切換攝像頭

  //擷取指定位置相機裝置
  - (AVCaptureDevice *)cameraWithPosition:(AVCaptureDevicePosition)position {
  
   NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
   for(AVCaptureDevice *device in devices){
       if(device.position == position){
           return device;
       }
   }
   return nil;
  }
  //是否可以切換攝像頭
  - (BOOL)canSwitchCamera {
   NSInteger count = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo].count;
   return (count>?YES:NO);
  }
  //沒有使用的攝像頭
  - (AVCaptureDevice *)inactiveCamera {
  
   AVCaptureDevice *device = nil;
   if([self canSwitchCamera]){
       if(self.videoDevice.position == AVCaptureDevicePositionBack){
           device = [self cameraWithPosition:AVCaptureDevicePositionFront];
       }else{
           device = [self cameraWithPosition:AVCaptureDevicePositionBack];
       }
   }
   return device;
  }
  //切換攝像頭
  - (void)swithCamera {
  
   if([self canSwitchCamera] == NO){
       return;
   }
  
   AVCaptureDevice *videoDevice = [self inactiveCamera];
   AVCaptureDeviceInput *videoDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:nil];
   if(videoDeviceInput){
  
       [self.session beginConfiguration];
       [self.session removeInput:_videoDeviceInput];
       if([self.session canAddInput:videoDeviceInput]){
  
           [self.session addInput:videoDeviceInput];
           _videoDevice = videoDevice;
           _videoDeviceInput = videoDeviceInput;
       }else{
           [self.session addInput:_videoDeviceInput];
       }
       [self.session commitConfiguration];
   }
             

  1. 設定聚焦點

  - (void)focusAtPoint:(CGPoint)point {
   //轉換為裝置坐标
   AVCaptureVideoPreviewLayer *layer = (AVCaptureVideoPreviewLayer *)self.layer;
   point = [layer captureDevicePointOfInterestForPoint:point];
  
   if(_videoDevice.focusPointOfInterestSupported && [_videoDevice isFocusModeSupported:(AVCaptureFocusModeAutoFocus)]){
  
       NSError *error = nil;
       if([_videoDevice lockForConfiguration:&error]){
  
           _videoDevice.focusPointOfInterest = point;
           _videoDevice.focusMode = AVCaptureFocusModeAutoFocus;
           [_videoDevice unlockForConfiguration];
       }
   }
  }
             

  1. 點選曝光

  - (void)exposeAtPoint:(CGPoint)point {
  
   AVCaptureVideoPreviewLayer *layer = (AVCaptureVideoPreviewLayer *)self.layer;
   point = [layer captureDevicePointOfInterestForPoint:point];
  
   if(_videoDevice.isExposurePointOfInterestSupported && [_videoDevice isExposureModeSupported:AVCaptureExposureModeAutoExpose]){
  
       NSError *error = nil;
       if([_videoDevice lockForConfiguration:&error]){
  
           _videoDevice.exposurePointOfInterest = point;
           _videoDevice.exposureMode = AVCaptureExposureModeAutoExpose;
           [_videoDevice unlockForConfiguration];
       }
   }
  }
             

  1. 設定閃光燈

  - (void)setFlashMode:(AVCaptureFlashMode)flashMode {
  
   if([_videoDevice isFlashModeSupported:flashMode]){
  
       NSError *error = nil;
       if([_videoDevice lockForConfiguration:&error]){
           _videoDevice.flashMode = flashMode;
           [_videoDevice unlockForConfiguration];
       }
   }
  }
             

  1. 設定手電筒

  - (void)setTorchMode:(AVCaptureTorchMode)torchMode {
  
   if([_videoDevice isTorchModeSupported:torchMode]){
  
       NSError *error = nil;
       if([_videoDevice lockForConfiguration:&error]){
           _videoDevice.torchMode = torchMode;
           [_videoDevice unlockForConfiguration];
       }
   }
  }
             

  1. 捕捉靜态圖檔

  - (void)captureStillImage {
  
     AVCaptureConnection *connection = [_stillImageOutPut connectionWithMediaType:AVMediaTypeVideo];
     //調整圖檔方向
     if(connection.isVideoOrientationSupported){
         connection.videoOrientation = [self currentVideoOrientation];
     }
  
     [_stillImageOutPut captureStillImageAsynchronouslyFromConnection:connection completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
  
         if(imageDataSampleBuffer != NULL){
             NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
             UIImage *image = [UIImage imageWithData:imageData];
         }
     }];
  }
  
  - (AVCaptureVideoOrientation)currentVideoOrientation {
  
     AVCaptureVideoOrientation orientation;
     switch ([UIDevice currentDevice].orientation) {
         case UIDeviceOrientationPortrait:{
             orientation = AVCaptureVideoOrientationPortrait;
             break;
         }
         case UIDeviceOrientationLandscapeRight:{
             orientation = AVCaptureVideoOrientationLandscapeRight;
             break;
         }
         case UIDeviceOrientationLandscapeLeft:{
             orientation = AVCaptureVideoOrientationLandscapeLeft;
             break;
         }
         default:
             orientation = AVCaptureVideoOrientationPortrait;
             break;
     }
     return orientation;
  }
             

  1. 開始停止錄制

  //開始錄制
  - (void)startRecoding {
  
     if(_videoDataOutPut.isRecording == NO){
  
         AVCaptureConnection *connection = [_videoDataOutPut connectionWithMediaType:AVMediaTypeVideo];
         //設定裝置旋轉
         if([connection isVideoOrientationSupported]){
             connection.videoOrientation = [self currentVideoOrientation];
         }
         //設定視訊穩定模式
         if([connection isVideoStabilizationSupported]){
             connection.preferredVideoStabilizationMode = AVCaptureVideoStabilizationModeAuto;
         }
         //平滑聚焦
         if(_videoDevice.isSmoothAutoFocusSupported){
             NSError *error = nil;
             if([_videoDevice lockForConfiguration:&error]){
                 _videoDevice.smoothAutoFocusEnabled = YES;
                 [_videoDevice unlockForConfiguration];
             }
         }
  
         NSURL *outputUrl = [NSURL URLWithString:@""];
         [_videoDataOutPut startRecordingToOutputFileURL:outputUrl recordingDelegate:self];
  
     }
  }
  //定制錄制
  - (void)stopRecording {
  
     if(_videoDataOutPut.isRecording){
         [_videoDataOutPut stopRecording];
     }
  }
             

  ​

  ​