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：
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= [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
//AVCaptureSessionPreset3840x2160
self.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; }return nil;}
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、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); } }}
5、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; }]; }]; }}
6、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
7、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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