1狱杰、首先聲明以下對象

import <AVFoundation/AVFoundation.h>

//捕獲設備瘦材，通常是前置攝像頭，后置攝像頭仿畸，麥克風（音頻輸入）
@property (nonatomic, strong) AVCaptureDevice *device;

//AVCaptureDeviceInput 代表輸入設備宇色，他使用AVCaptureDevice 來初始化
@property (nonatomic, strong) AVCaptureDeviceInput *input;

//輸出圖片
@property (nonatomic ,strong) AVCaptureStillImageOutput *imageOutput;

//session：由他把輸入輸出結合在一起，并開始啟動捕獲設備（攝像頭）
@property (nonatomic, strong) AVCaptureSession *session;

//圖像預覽層颁湖，實時顯示捕獲的圖像
@property (nonatomic ,strong) AVCaptureVideoPreviewLayer *previewLayer;

2宣蠕、初始化各個對象

• (void)cameraDistrict
  {
  // AVCaptureDevicePositionBack 后置攝像頭
  // AVCaptureDevicePositionFront 前置攝像頭
  self.device = [self cameraWithPosition:AVCaptureDevicePositionFront];
  self.input = [[AVCaptureDeviceInput alloc] initWithDevice:self.device error:nil];

self.imageOutput = [[AVCaptureStillImageOutput alloc] init];

self.session = [[AVCaptureSession alloc] init];
// 拿到的圖像的大小可以自行設定
// AVCaptureSessionPreset320x240
// AVCaptureSessionPreset352x288
// AVCaptureSessionPreset640x480
// AVCaptureSessionPreset960x540
// AVCaptureSessionPreset1280x720
// AVCaptureSessionPreset1920x1080
// AVCaptureSessionPreset3840x2160
self.session.sessionPreset = AVCaptureSessionPreset640x480;
//輸入輸出設備結合
if ([self.session canAddInput:self.input]) {
[self.session addInput:self.input];
}
if ([self.session canAddOutput:self.imageOutput]) {
[self.session addOutput:self.imageOutput];
}
//預覽層的生成
self.previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.session];
self.previewLayer.frame = CGRectMake(0, 64, SCREEN_WIDTH, SCREEN_HEIGHT-64);
self.previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
[self.view.layer addSublayer:self.previewLayer];
//設備取景開始
[self.session startRunning];
if ([_device lockForConfiguration:nil]) {
//自動閃光燈，
if ([_device isFlashModeSupported:AVCaptureFlashModeAuto]) {
[_device setFlashMode:AVCaptureFlashModeAuto];
}
//自動白平衡,但是好像一直都進不去
if ([_device isWhiteBalanceModeSupported:AVCaptureWhiteBalanceModeAutoWhiteBalance]) {
[_device setWhiteBalanceMode:AVCaptureWhiteBalanceModeAutoWhiteBalance];
}
[_device unlockForConfiguration];
}

}

根據(jù)前后置位置拿到相應的攝像頭：

• (AVCaptureDevice *)cameraWithPosition:(AVCaptureDevicePosition)position{
  NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
  for ( AVCaptureDevice *device in devices )
  if ( device.position == position ){
  return device;
  }
  return nil;
  }

3甥捺、拍照拿到相應圖片：

• (void)photoBtnDidClick
  {
  AVCaptureConnection *conntion = [self.imageOutput connectionWithMediaType:AVMediaTypeVideo];
  if (!conntion) {
  NSLog(@"拍照失敗!");
  return;
  }
  [self.imageOutput captureStillImageAsynchronouslyFromConnection:conntion completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
  if (imageDataSampleBuffer == nil) {
  return ;
  }
  NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
  self.image = [UIImage imageWithData:imageData];
  [self.session stopRunning];
  [self.view addSubview:self.cameraImageView];
  }

4抢蚀、保存照片到相冊：

pragma - 保存至相冊

• (void)saveImageToPhotoAlbum:(UIImage*)savedImage
  {

UIImageWriteToSavedPhotosAlbum(savedImage, self, @selector(image:didFinishSavingWithError:contextInfo:), NULL);

}
// 指定回調(diào)方法

• (void)image: (UIImage *) image didFinishSavingWithError: (NSError *) error contextInfo: (void *) contextInfo

{
NSString *msg = nil ;
if(error != NULL){
msg = @"保存圖片失敗" ;
}else{
msg = @"保存圖片成功" ;
}
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"保存圖片結果提示"
message:msg
delegate:self
cancelButtonTitle:@"確定"
otherButtonTitles:nil];
[alert show];
}

5、前后置攝像頭的切換

• (void)changeCamera{
  NSUInteger cameraCount = [[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo] count];
  if (cameraCount > 1) {
  NSError *error;
  //給攝像頭的切換添加翻轉動畫
  CATransition *animation = [CATransition animation]镰禾；
  animation.duration = .5f皿曲；
  animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
  animation.type = @"oglFlip";

  AVCaptureDevice *newCamera = nil;
  AVCaptureDeviceInput *newInput = nil;
  //拿到另外一個攝像頭位置
  AVCaptureDevicePosition position = [[_input device] position];
  if (position == AVCaptureDevicePositionFront){
  newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack];
  animation.subtype = kCATransitionFromLeft;//動畫翻轉方向
  }
  else {
  newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront];
  animation.subtype = kCATransitionFromRight;//動畫翻轉方向
  }
  //生成新的輸入
  newInput = [AVCaptureDeviceInput deviceInputWithDevice:newCamera error:nil];
  [self.previewLayer addAnimation:animation forKey:nil];
  if (newInput != nil) {
  [self.session beginConfiguration];
  [self.session removeInput:self.input];
  if ([self.session canAddInput:newInput]) {
  [self.session addInput:newInput];
  self.input = newInput;

  } else {
  [self.session addInput:self.input];
  }
  [self.session commitConfiguration];

  } else if (error) {
  NSLog(@"toggle carema failed, error = %@", error);
  }
  }
  }

6唱逢、相機的其它參數(shù)設置
//AVCaptureFlashMode 閃光燈
//AVCaptureFocusMode 對焦
//AVCaptureExposureMode 曝光
//AVCaptureWhiteBalanceMode 白平衡
//閃光燈和白平衡可以在生成相機時候設置
//曝光要根據(jù)對焦點的光線狀況而決定,所以和對焦一塊寫
//point為點擊的位置

• (void)focusAtPoint:(CGPoint)point{
  CGSize size = self.view.bounds.size;
  CGPoint focusPoint = CGPointMake( point.y /size.height ,1-point.x/size.width );
  NSError *error;
  if ([self.device lockForConfiguration:&error]) {
  //對焦模式和對焦點
  if ([self.device isFocusModeSupported:AVCaptureFocusModeAutoFocus]) {
  [self.device setFocusPointOfInterest:focusPoint];
  [self.device setFocusMode:AVCaptureFocusModeAutoFocus];
  }
  //曝光模式和曝光點
  if ([self.device isExposureModeSupported:AVCaptureExposureModeAutoExpose ]) {
  [self.device setExposurePointOfInterest:focusPoint];
  [self.device setExposureMode:AVCaptureExposureModeAutoExpose];
  }

  [self.device unlockForConfiguration];
  //設置對焦動畫
  _focusView.center = point;
  _focusView.hidden = NO;
  [UIView animateWithDuration:0.3 animations:^{
  _focusView.transform = CGAffineTransformMakeScale(1.25, 1.25);
  }completion:^(BOOL finished) {
  [UIView animateWithDuration:0.5 animations:^{
  _focusView.transform = CGAffineTransformIdentity;
  } completion:^(BOOL finished) {
  _focusView.hidden = YES;
  }];
  }];
  }

}

7、遇到的一些坑和解決辦法

1. 前后置攝像頭的切換

前后值不能切換屋休，各種嘗試找了半天沒找到有原因坞古。后來發(fā)現(xiàn)我在設置圖片尺寸的時候設置為1080P [self.session canSetSessionPreset: AVCaptureSessionPreset1920x1080] ，前置攝像頭并不支持這么大的尺寸劫樟，所以就不能切換前置攝像頭痪枫。我驗證了下 前置攝像頭最高支持720P,720P以內(nèi)可自由切換。

當然也可以在前后置攝像頭切換的時候叠艳，根據(jù)前后攝像頭來設置不同的尺寸奶陈，這里不在贅述。

2）焦點位置

CGPoint focusPoint = CGPointMake( point.y /size.height ,1-point.x/size.width );
setExposurePointOfInterest：focusPoint 函數(shù)后面Point取值范圍是取景框左上角（0附较，0）到取景框右下角（1吃粒，1）之間。官方是這么寫的：

The value of this property is a CGPoint that determines the receiver's focus point of interest, if it has one. A value of (0,0) indicates that the camera should focus on the top left corner of the image, while a value of (1,1) indicates that it should focus on the bottom right. The default value is (0.5,0.5).