1、首先声明以下对象

#import//捕获设备，通常是前置摄像头，后置摄像头，麦克风（音频输入）@property(nonatomic,strong)AVCaptureDevice*device;//AVCaptureDeviceInput 代表输入设备，他使用AVCaptureDevice 来初始化@property(nonatomic,strong)AVCaptureDeviceInput*input;//输出图片@property(nonatomic,strong)AVCaptureStillImageOutput*imageOutput;//session：由他把输入输出结合在一起，并开始启动捕获设备（摄像头）@property(nonatomic,strong)AVCaptureSession*session;//图像预览层，实时显示捕获的图像@property(nonatomic,strong)AVCaptureVideoPreviewLayer*previewLayer;

2、初始化各个对象

- (void)cameraDistrict{//    AVCaptureDevicePositionBack  后置摄像头//    AVCaptureDevicePositionFront 前置摄像头self.device= [selfcameraWithPosition:AVCaptureDevicePositionFront];self.input= [[AVCaptureDeviceInputalloc] initWithDevice:self.deviceerror:nil];self.imageOutput= [[AVCaptureStillImageOutputalloc] init];self.session= [[AVCaptureSessionalloc] init];//    拿到的图像的大小可以自行设定//    AVCaptureSessionPreset320x240//    AVCaptureSessionPreset352x288//    AVCaptureSessionPreset640x480//    AVCaptureSessionPreset960x540//    AVCaptureSessionPreset1280x720//    AVCaptureSessionPreset1920x1080//    AVCaptureSessionPreset3840x2160self.session.sessionPreset=AVCaptureSessionPreset640x480;//输入输出设备结合if([self.sessioncanAddInput:self.input]) {        [self.sessionaddInput:self.input];    }if([self.sessioncanAddOutput:self.imageOutput]) {        [self.sessionaddOutput:self.imageOutput];    }//预览层的生成self.previewLayer= [[AVCaptureVideoPreviewLayeralloc] initWithSession:self.session];self.previewLayer.frame=CGRectMake(0,64, SCREEN_WIDTH, SCREEN_HEIGHT-64);self.previewLayer.videoGravity=AVLayerVideoGravityResizeAspectFill;    [self.view.layeraddSublayer:self.previewLayer];//设备取景开始[self.sessionstartRunning];if([_device lockForConfiguration:nil]) {//自动闪光灯，if([_device isFlashModeSupported:AVCaptureFlashModeAuto]) {            [_device setFlashMode:AVCaptureFlashModeAuto];        }//自动白平衡,但是好像一直都进不去if([_device isWhiteBalanceModeSupported:AVCaptureWhiteBalanceModeAutoWhiteBalance]) {            [_device setWhiteBalanceMode:AVCaptureWhiteBalanceModeAutoWhiteBalance];        }        [_device unlockForConfiguration];    }}

根据前后置位置拿到相应的摄像头：

- (AVCaptureDevice*)cameraWithPosition:(AVCaptureDevicePosition)position{NSArray*devices = [AVCaptureDevicedevicesWithMediaType:AVMediaTypeVideo];for(AVCaptureDevice*deviceindevices )if( device.position== position ){returndevice;        }returnnil;}

3、拍照拿到相应图片：

- (void)photoBtnDidClick{AVCaptureConnection*conntion = [self.imageOutputconnectionWithMediaType:AVMediaTypeVideo];if(!conntion) {NSLog(@"拍照失败!");return;          }    [self.imageOutputcaptureStillImageAsynchronouslyFromConnection:conntion completionHandler:^(CMSampleBufferRef imageDataSampleBuffer,NSError*error) {if(imageDataSampleBuffer ==nil) {return;          }NSData*imageData = [AVCaptureStillImageOutputjpegStillImageNSDataRepresentation:imageDataSampleBuffer];self.image= [UIImageimageWithData:imageData];        [self.sessionstopRunning];        [self.viewaddSubview:self.cameraImageView];}

4、保存照片到相册：

#pragma - 保存至相册- (void)saveImageToPhotoAlbum:(UIImage*)savedImage{UIImageWriteToSavedPhotosAlbum(savedImage,self,@selector(image:didFinishSavingWithError:contextInfo:),NULL);}// 指定回调方法- (void)image: (UIImage*) image didFinishSavingWithError: (NSError*) error contextInfo: (void*) contextInfo{NSString*msg =nil;if(error !=NULL){        msg =@"保存图片失败";    }else{        msg =@"保存图片成功";    }UIAlertView*alert = [[UIAlertViewalloc] initWithTitle:@"保存图片结果提示"message:msg                                            delegate:selfcancelButtonTitle:@"确定"otherButtonTitles:nil];    [alert show];}

5、前后置摄像头的切换

- (void)changeCamera{NSUIntegercameraCount = [[AVCaptureDevicedevicesWithMediaType:AVMediaTypeVideo] count];if(cameraCount >1) {NSError*error;//给摄像头的切换添加翻转动画CATransition*animation = [CATransitionanimation]；        animation.duration=.5f；        animation.timingFunction= [CAMediaTimingFunctionfunctionWithName:kCAMediaTimingFunctionEaseInEaseOut];        animation.type=@"oglFlip";AVCaptureDevice*newCamera =nil;AVCaptureDeviceInput*newInput =nil;//拿到另外一个摄像头位置AVCaptureDevicePositionposition = [[_input device] position];if(position ==AVCaptureDevicePositionFront){            newCamera = [selfcameraWithPosition:AVCaptureDevicePositionBack];            animation.subtype= kCATransitionFromLeft;//动画翻转方向}else{            newCamera = [selfcameraWithPosition:AVCaptureDevicePositionFront];            animation.subtype= kCATransitionFromRight;//动画翻转方向}//生成新的输入newInput = [AVCaptureDeviceInputdeviceInputWithDevice:newCamera error:nil];        [self.previewLayeraddAnimation:animation forKey:nil];if(newInput !=nil) {            [self.sessionbeginConfiguration];            [self.sessionremoveInput:self.input];if([self.sessioncanAddInput:newInput]) {                [self.sessionaddInput:newInput];self.input= newInput;            }else{                [self.sessionaddInput:self.input];            }            [self.sessioncommitConfiguration];        }elseif(error) {NSLog(@"toggle carema failed, error = %@", error);        }    }}

6、相机的其它参数设置

//AVCaptureFlashMode  闪光灯//AVCaptureFocusMode  对焦//AVCaptureExposureMode  曝光//AVCaptureWhiteBalanceMode  白平衡//闪光灯和白平衡可以在生成相机时候设置//曝光要根据对焦点的光线状况而决定,所以和对焦一块写//point为点击的位置- (void)focusAtPoint:(CGPoint)point{CGSizesize =self.view.bounds.size;CGPointfocusPoint =CGPointMake( point.y/size.height,1-point.x/size.width);NSError*error;if([self.devicelockForConfiguration:&error]) {//对焦模式和对焦点if([self.deviceisFocusModeSupported:AVCaptureFocusModeAutoFocus]) {            [self.devicesetFocusPointOfInterest:focusPoint];            [self.devicesetFocusMode:AVCaptureFocusModeAutoFocus];        }//曝光模式和曝光点if([self.deviceisExposureModeSupported:AVCaptureExposureModeAutoExpose]) {            [self.devicesetExposurePointOfInterest:focusPoint];            [self.devicesetExposureMode:AVCaptureExposureModeAutoExpose];        }        [self.deviceunlockForConfiguration];//设置对焦动画_focusView.center= point;        _focusView.hidden=NO;        [UIViewanimateWithDuration:0.3animations:^{            _focusView.transform=CGAffineTransformMakeScale(1.25,1.25);        }completion:^(BOOLfinished) {            [UIViewanimateWithDuration:0.5animations:^{                _focusView.transform=CGAffineTransformIdentity;            } completion:^(BOOLfinished) {                _focusView.hidden=YES;            }];        }];    }}

7、遇到的一些坑和解决办法

1) 前后置摄像头的切换

前后值不能切换，各种尝试找了半天没找到有原因。后来发现我在设置图片尺寸的时候设置为1080P [self.session canSetSessionPreset: AVCaptureSessionPreset1920x1080]  ，前置摄像头并不支持这么大的尺寸，所以就不能切换前置摄像头。我验证了下 前置摄像头最高支持720P,720P以内可自由切换。　　当然也可以在前后置摄像头切换的时候，根据前后摄像头来设置不同的尺寸，这里不在赘述。

2）焦点位置

CGPoint focusPoint = CGPointMake( point.y /size.height ,1-point.x/size.width );

setExposurePointOfInterest：focusPoint 函数后面Point取值范围是取景框左上角（0，0）到取景框右下角（1，1）之间。官方是这么写的：

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).

我也试了按这个来但位置就是不对，只能按上面的写法才可以。前面是点击位置的y/PreviewLayer的高度，后面是1-点击位置的x/PreviewLayer的宽度

3）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。

曝光同上

8、写在最后

附上demo:https://github.com/nanshanyi/photographDemo

常用到的基本就这么多，写的并不完善，有什么不对的，欢迎大家批评指正，共同学习。

文／_南山忆（简书作者）

原文链接：http://www.jianshu.com/p/8b28892bae5a

著作权归作者所有，转载请联系作者获得授权，并标注“简书作者”。