iOS自定义相机

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　　最近公司的项目中用到了相机，由于不用系统的相机，UI给的相机切图，必须自定义才可以。就花时间简单研究了一下相机的自定义。
　　相机属于系统硬件，这就需要我们来手动调用iPhone的相机硬件，分为以下步骤：

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1、首先声明以下对象

#import <AVFoundation/AVFoundation.h>//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 = [self cameraWithPosition:AVCaptureDevicePositionFront];    self.input = [[AVCaptureDeviceInput alloc] initWithDevice:self.device error:nil];    self.imageOutput = [[AVCaptureStillImageOutput alloc] init];    self.session = [[AVCaptureSession alloc] init];    //     拿到的图像的大小可以自行设定    //    AVCaptureSessionPreset320x240    //    AVCaptureSessionPreset352x288    //    AVCaptureSessionPreset640x480    //    AVCaptureSessionPreset960x540    //    AVCaptureSessionPreset1280x720    //    AVCaptureSessionPreset1920x1080    //    AVCaptureSessionPreset3840x2160    self.session.sessionPreset = AVCaptureSessionPreset640x480;    //输入输出设备结合    if ([self.session canAddInput:self.input]) {        [self.session addInput:self.input];    }    if ([self.session canAddOutput:self.imageOutput]) {        [self.session addOutput:self.imageOutput];    }    //预览层的生成    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];    //设备取景开始    [self.session startRunning];    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 = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];    for ( AVCaptureDevice *device in devices )        if ( device.position == position ){            return device;        }    return nil;}3、拍照拿到相应图片：- (void)photoBtnDidClick{    AVCaptureConnection *conntion = [self.imageOutput connectionWithMediaType:AVMediaTypeVideo];      if (!conntion) {          NSLog(@"拍照失败!");          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、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 = [[UIAlertView alloc] initWithTitle:@"保存图片结果提示"                                            message:msg                                            delegate:self                                          cancelButtonTitle:@"确定"                                          otherButtonTitles:nil];    [alert show];}

5、前后置摄像头的切换

- (void)changeCamera{    NSUInteger cameraCount = [[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo] count];    if (cameraCount > 1) {        NSError *error;        //给摄像头的切换添加翻转动画        CATransition *animation = [CATransition animation]；        animation.duration = .5f；        animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];        animation.type = @"oglFlip";        AVCaptureDevice *newCamera = nil;        AVCaptureDeviceInput *newInput = nil;  //拿到另外一个摄像头位置        AVCaptureDevicePosition position = [[_input device] position];        if (position == AVCaptureDevicePositionFront){            newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack];            animation.subtype = kCATransitionFromLeft;//动画翻转方向        }        else {            newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront];            animation.subtype = kCATransitionFromRight;//动画翻转方向        }        //生成新的输入        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、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{    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]) {        //对焦模式和对焦点        if ([self.device isFocusModeSupported:AVCaptureFocusModeAutoFocus]) {            [self.device setFocusPointOfInterest:focusPoint];            [self.device setFocusMode:AVCaptureFocusModeAutoFocus];        }        //曝光模式和曝光点        if ([self.device isExposureModeSupported:AVCaptureExposureModeAutoExpose ]) {            [self.device setExposurePointOfInterest:focusPoint];            [self.device setExposureMode:AVCaptureExposureModeAutoExpose];        }        [self.device unlockForConfiguration];        //设置对焦动画        _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。

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