AVCaptureDevice.h，主要用来获取iphone一些关于相机设备的属性。AVCaptureDevice.h，必须要引入AVFoundation.framework包。
1. 前置和后置摄像头
enum {
AVCaptureDevicePositionBack = 1,
AVCaptureDevicePositionFront = 2
};typedef NSInteger AVCaptureDevicePosition;
2. 闪光灯开关
enum {
AVCaptureFlashModeOff = 0,
AVCaptureFlashModeOn = 1,
AVCaptureFlashModeAuto = 2
};typedef NSInteger AVCaptureFlashMode;
3. 手电筒开关
enum {
AVCaptureTorchModelOff = 0,
AVCaptureTorchModelOn = 1,
AVCaptureTorchModeAuto = 2
};typedef NSInteger AVCaptureTorchMode;
4. 焦距调整
enum {
AVCaptureFocusModelLocked = 0,
AVCaptureFocusModeAutoFocus = 1, AVCaptureFocusModeContinousAutoFocus = 2
};typedef NSInteger AVCaptureFocusMode;
5. 曝光量调节
enum {
AVCaptureExposureModeLocked = 0,
AVCaptureExposureModeAutoExpose = 1, AVCaptureExposureModeContinuousAutoExposure = 2
};typedef NSInteger AVCaptureExposureMode;
6. 白平衡
enum {
AVCaptureWhiteBalanceModeLocked = 0, AVCaptureWhiteBalanceModeAutoWhiteBalance = 1, AVCaptureWhiteBalanceModeContinuousAutoWhiteBalance = 2
};typedef NSInteger AVCaptureWhiteBalanceMode;