关于自定义相机的整理

  前言 

　　 为什么不用系统相机要用自定义相机呢？

　　由于系统相机功能单一，界面简单，在开发的过程中为了达到更好的个性化交互设计，符合app主题，提供更多更有趣的功能时候，我们会采用自定义相机。来达到更好的界面效果，更好的用户体验。接下来说说整个自定义相机过程，以及遇到的一些问题。

  概览

1，流程

2，详细各部分

• 初始化，建立会话，获取摄像头
• 嵌入实时预览图层
• 相关设置
• 拍摄获取照片
• UIView层及UI交互

3，遇到的坑

  流程

　　AVCaptureSession通过把设备的麦克风/摄像头(AVCaptureDevice)实例化成数据流输入对象(AVCaptureDeviceInput)后,再通过建立连接(AVCaptionConnection)将录制数据通过数据流输出对象(AVCaptureOutput)导出,而录制的时候咱们可以同步预览当前的录制界面(AVCaptureVideoPreviewLayer).

输出图像的时候需要用到AVCaptureConnection这个类，session通过AVCaptureConnection连接AVCaptureStillImageOutput进行图片输出，输入输出与connection的关系如下图

   详细各部分

 　　1.初始化，建立会话，获取摄像头

- (AVCaptureSession *)recordSession {
    if (_recordSession == nil) {
        _recordSession = [[AVCaptureSession alloc] init];
        if ([_recordSession canAddInput:self.backCameraInput]) {
               [_recordSession addInput:self.backCameraInput];
        }
      
         //将输入设备加入会话
         if ([_recordSession canAddOutput:self.imageOutput]) {
               [_recordSession addOutput:self.imageOutput];
         }

         //设置分辨率
         if ([_recordSession canSetSessionPreset:AVCaptureSessionPresetPhoto]) {
                    [_recordSession setSessionPreset:AVCaptureSessionPresetPhoto];
         }
    }
}

//后置摄像头输入
- (AVCaptureDeviceInput *)backCameraInput {
    if (_backCameraInput == nil) {
        NSError *error;
        _backCameraInput = [[AVCaptureDeviceInput alloc] initWithDevice:[self backCamera] error:&error];
        if (error) {
            NSLog(@"获取后置摄像头失败~");
        }
    }
    return _backCameraInput;
}

//建立输出设备
- (AVCaptureStillImageOutput *)imageOutput {
    if (_imageOutput == nil) {
        _imageOutput = [[AVCaptureStillImageOutput alloc]init];
        NSDictionary *settingDic = @{AVVideoCodecKey:AVVideoCodecJPEG};
        _imageOutput.outputSettings = settingDic;

    }
    return _imageOutput;
}

　　2.嵌入实时预览层

//捕获到的视频呈现的layer
- (AVCaptureVideoPreviewLayer *)previewLayer {
    if (_previewLayer == nil) {
        //通过AVCaptureSession初始化
        AVCaptureVideoPreviewLayer *preview = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.recordSession];
        //AVLayerVideoGravityResizeAspect
        //设置比例为铺满全屏AVLayerVideoGravityResizeAspectFill
        //设置比例为和预览layer一样大小 AVLayerVideoGravityResize
        preview.videoGravity = AVLayerVideoGravityResizeAspectFill;
        _previewLayer = preview;
    }
    return _previewLayer;
}

　　

　　3.相关设置

//切换前后置摄像头
- (void)changeCameraInputDeviceisFront:(BOOL)isFront {
    if (isFront) {
        [self.recordSession stopRunning];
        [self.recordSession removeInput:self.backCameraInput];
        if ([self.recordSession canAddInput:self.frontCameraInput]) {
            [self changeCameraAnimation];
            [self.recordSession addInput:self.frontCameraInput];

        }
    } else {
        [self.recordSession stopRunning];
        [self.recordSession removeInput:self.frontCameraInput];
        if ([self.recordSession canAddInput:self.backCameraInput]) {
            [self changeCameraAnimation];
            [self.recordSession addInput:self.backCameraInput];
        }
    }
}

//开启闪光灯
- (void)openFlashLight {
    AVCaptureDevice *backCamera = [self backCamera];
    if (backCamera.flashMode == AVCaptureFlashModeOff) {
        [backCamera lockForConfiguration:nil];
        //        backCamera.torchMode = AVCaptureTorchModeOn;
        backCamera.flashMode = AVCaptureFlashModeOn;
        [backCamera unlockForConfiguration];
    }
}

//关闭闪光灯
- (void)closeFlashLight {
    AVCaptureDevice *backCamera = [self backCamera];
    if (backCamera.flashMode == AVCaptureFlashModeOn) {
        [backCamera lockForConfiguration:nil];
        //        backCamera.torchMode = AVCaptureTorchModeOff;
        backCamera.flashMode = AVCaptureFlashModeOff;
        [backCamera unlockForConfiguration];
    }
}

//聚焦
- (void)focusWithPoint:(CGPoint)aPoint {
    CGPoint focusPoint = [self.previewLayer captureDevicePointOfInterestForPoint:aPoint];
    AVCaptureDevice *device = [self.recordSession.inputs.lastObject device];
    if (device.isFocusPointOfInterestSupported && [device isFocusModeSupported:AVCaptureFocusModeAutoFocus]) {
        if ([device lockForConfiguration:nil]) {
            device.focusPointOfInterest = focusPoint;
            device.focusMode = AVCaptureFocusModeContinuousAutoFocus;
            [device unlockForConfiguration];
        }
    }
}

　　4.拍摄获取照片

- (void)takePhoto {
    AVCaptureConnection *connection = [self.imageOutput connectionWithMediaType:AVMediaTypeVideo];
    if (connection.isVideoOrientationSupported) {
        connection.videoOrientation = [self currentVideoOrientation];

    }
    if ([connection isVideoStabilizationSupported]) {
        connection.preferredVideoStabilizationMode = AVCaptureVideoStabilizationModeCinematic;
    }
    [self.imageOutput captureStillImageAsynchronouslyFromConnection:connection completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
        UIImage *image = nil;
        NSData *data = nil;
        if (imageDataSampleBuffer != NULL) {
            data  = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
            image = [UIImage imageWithData:data];
        }
    }];
}

  遇到的坑

1，设置特殊分辨率的，再切换到前置摄像头闪退

　　这个问题的原因在于前置摄像头不具备后置摄像头的高分辨率时，切换时就会闪退，所以在切换摄像头时要判断摄像头支持的分辨率。

2，对焦和曝光

　　我在设置对焦是 先设置了模式setFocusMode，后设置对焦位置，就会导致很奇怪的现象，对焦位置是你上次点击的位置。所以一定要先设置位置，再设置对焦模式。

3，焦点位置

　　点击屏幕时的焦点，要对应转化成摄像头上的坐标位置