iOS使用AVCaptureSession自定义相机

关于iOS调用摄像机来获取照片，通常我们都会调用UIImagePickerController来调用系统提供的相机来拍照，这个控件非常好用。但是有时UIImagePickerController控件无法满足我们的需求，例如我们需要更加复杂的OverlayerView，这时候我们就要自己构造一个摄像机控件了。

这需要使用AVFoundation.framework这个framework里面的组件了，所以我们先要导入这个头文件，另外还需要的组件官方文档是这么说的：

● An instance of AVCaptureDevice to represent the input device, such as a camera or microphone
● An instance of a concrete subclass of AVCaptureInput to configure the ports from the input device
● An instance of a concrete subclass of AVCaptureOutput to manage the output to a movie file or still image
● An instance of AVCaptureSession to coordinate the data flow from the input to the output

这里我只构造了一个具有拍照功能的照相机，至于录影和录音功能这里就不加说明了。

总结下来，我们需要以下的对象：

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@property (nonatomic, strong)       AVCaptureSession            * session; //AVCaptureSession对象来执行输入设备和输出设备之间的数据传递 @property (nonatomic, strong)       AVCaptureDeviceInput        * videoInput; //AVCaptureDeviceInput对象是输入流 @property (nonatomic, strong)       AVCaptureStillImageOutput   * stillImageOutput; //照片输出流对象，当然我的照相机只有拍照功能，所以只需要这个对象就够了 @property (nonatomic, strong)       AVCaptureVideoPreviewLayer  * previewLayer; //预览图层，来显示照相机拍摄到的画面 @property (nonatomic, strong)       UIBarButtonItem             * toggleButton; //切换前后镜头的按钮 @property (nonatomic, strong)       UIButton                    * shutterButton; //拍照按钮 @property (nonatomic, strong)       UIView                      * cameraShowView; //放置预览图层的View

我的习惯是在init方法执行的时候创建这些对象，然后在viewWillAppear方法里加载预览图层。现在就让我们看一下代码就清楚了。

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- (void) initialSession {     //这个方法的执行我放在init方法里了     self.session = [[AVCaptureSession alloc] init];     self.videoInput = [[AVCaptureDeviceInput alloc] initWithDevice:[self frontCamera] error:nil];     //[self fronCamera]方法会返回一个AVCaptureDevice对象，因为我初始化时是采用前摄像头，所以这么写，具体的实现方法后面会介绍     self.stillImageOutput = [[AVCaptureStillImageOutput alloc] init];     NSDictionary * outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys:AVVideoCodecJPEG,AVVideoCodecKey, nil];     //这是输出流的设置参数AVVideoCodecJPEG参数表示以JPEG的图片格式输出图片     [self.stillImageOutput setOutputSettings:outputSettings];           if ([self.session canAddInput:self.videoInput]) {         [self.session addInput:self.videoInput];     }     if ([self.session canAddOutput:self.stillImageOutput]) {         [self.session addOutput:self.stillImageOutput];     }       }

这是获取前后摄像头对象的方法

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- (AVCaptureDevice *)cameraWithPosition:(AVCaptureDevicePosition) position {     NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];     for (AVCaptureDevice *device in devices) {         if ([device position] == position) {             return device;         }     }     return nil; }     - (AVCaptureDevice *)frontCamera {     return [self cameraWithPosition:AVCaptureDevicePositionFront]; }   - (AVCaptureDevice *)backCamera {     return [self cameraWithPosition:AVCaptureDevicePositionBack]; }

接下来在viewWillAppear方法里执行加载预览图层的方法

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- (void) setUpCameraLayer {     if (_cameraAvaible == NO) return;           if (self.previewLayer == nil) {         self.previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.session];         UIView * view = self.cameraShowView;         CALayer * viewLayer = [view layer];         [viewLayer setMasksToBounds:YES];                   CGRect bounds = [view bounds];         [self.previewLayer setFrame:bounds];         [self.previewLayer setVideoGravity:AVLayerVideoGravityResizeAspect];                   [viewLayer insertSublayer:self.previewLayer below:[[viewLayer sublayers] objectAtIndex:0]];               } }

注意以下的方法，在viewDidAppear和viewDidDisappear方法中启动和关闭session

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- (void) viewDidAppear:(BOOL)animated {     [super viewDidAppear:animated];     if (self.session) {         [self.session startRunning];     } }   - (void) viewDidDisappear:(BOOL)animated {     [super viewDidDisappear: animated];     if (self.session) {         [self.session stopRunning];     } }

接着我们就来实现切换前后镜头的按钮，按钮的创建我就不多说了

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- (void)toggleCamera {     NSUInteger cameraCount = [[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo] count];     if (cameraCount > 1) {         NSError *error;         AVCaptureDeviceInput *newVideoInput;         AVCaptureDevicePosition position = [[_videoInput device] position];                   if (position == AVCaptureDevicePositionBack)             newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:[self frontCamera] error:&error];         else if (position == AVCaptureDevicePositionFront)             newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:[self backCamera] error:&error];         else             return;                   if (newVideoInput != nil) {             [self.session beginConfiguration];             [self.session removeInput:self.videoInput];             if ([self.session canAddInput:newVideoInput]) {                 [self.session addInput:newVideoInput];                 [self setVideoInput:newVideoInput];             } else {                 [self.session addInput:self.videoInput];             }             [self.session commitConfiguration];         } else if (error) {             NSLog(@"toggle carema failed, error = %@", error);         }     } }

这是切换镜头的按钮方法

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- (void) shutterCamera {     AVCaptureConnection * videoConnection = [self.stillImageOutput connectionWithMediaType:AVMediaTypeVideo];     if (!videoConnection) {         NSLog(@"take photo failed!");         return;     }           [self.stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {         if (imageDataSampleBuffer == NULL) {             return;         }         NSData * imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];         UIImage * image = [UIImage imageWithData:imageData];         NSLog(@"image size = %@",NSStringFromCGSize(image.size));     }]; } http://www.2cto.com/kf/201409/335951.html

这是拍照按钮的方法