iOS 相机相关

这里不说拍照这种大家都烂熟的东西，主要说说图像预览、人脸识别、二维码识别等，都是基于AVFoundation框架实现的。
引入 ：#import
开启相机权限：
1.在项目中找到info.plist文件，右键点击以 Source Code形式打开
2.添加以下键值对

    NSCameraUsageDescription
    此 App 需要相机权限

主要属性：

//硬件设备
@property (nonatomic, strong) AVCaptureDevice *device;
//输入流
@property (nonatomic, strong) AVCaptureDeviceInput *input;
//协调输入输出流的数据
@property (nonatomic, strong) AVCaptureSession *session;
//预览层
@property (nonatomic, strong) AVCaptureVideoPreviewLayer *previewLayer;

//输出流
@property (nonatomic, strong) AVCaptureStillImageOutput *stillImageOutput;  //用于捕捉静态图片
@property (nonatomic, strong) AVCaptureVideoDataOutput *videoDataOutput;    //原始视频帧，用于获取实时图像以及视频录制
@property (nonatomic, strong) AVCaptureMetadataOutput *metadataOutput;      //用于二维码识别以及人脸识别

首先我们需要在手机上把图像显示出来

1.1 获取硬件设备

-(AVCaptureDevice *)device{
 if (_device == nil) {
     _device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
//(注意调整device属性的时候需要上锁, 调整完再解锁)
     if ([_device lockForConfiguration:nil]) {
         //自动闪光灯
         if ([_device isFlashModeSupported:AVCaptureFlashModeAuto]) {
             [_device setFlashMode:AVCaptureFlashModeAuto];
         }
         //自动白平衡
         if ([_device isWhiteBalanceModeSupported:AVCaptureWhiteBalanceModeContinuousAutoWhiteBalance]) {
             [_device setWhiteBalanceMode:AVCaptureWhiteBalanceModeContinuousAutoWhiteBalance];
         }
         //自动对焦
         if ([_device isFocusModeSupported:AVCaptureFocusModeContinuousAutoFocus]) {
             [_device setFocusMode:AVCaptureFocusModeContinuousAutoFocus];
         }
         //自动曝光
         if ([_device isExposureModeSupported:AVCaptureExposureModeContinuousAutoExposure]) {
             [_device setExposureMode:AVCaptureExposureModeContinuousAutoExposure];
         }
         [_device unlockForConfiguration];
     }
 }
 return _device;
}

device相关属性选项：
闪光灯选项

typedef NS_ENUM(NSInteger, AVCaptureFlashMode) {
AVCaptureFlashModeOff  = 0,//关
AVCaptureFlashModeOn   = 1,//开
AVCaptureFlashModeAuto = 2//自动
} NS_AVAILABLE(10_7, 4_0) __TVOS_PROHIBITED;

前后置摄像头选项

typedef NS_ENUM(NSInteger, AVCaptureDevicePosition) {
AVCaptureDevicePositionUnspecified         = 0,//不指定
AVCaptureDevicePositionBack                = 1,//后置摄像头
AVCaptureDevicePositionFront               = 2//前
} NS_AVAILABLE(10_7, 4_0) __TVOS_PROHIBITED;

手电筒选项

typedef NS_ENUM(NSInteger, AVCaptureTorchMode) {
AVCaptureTorchModeOff  = 0,//开
AVCaptureTorchModeOn   = 1,//关
AVCaptureTorchModeAuto = 2,//自动
} NS_AVAILABLE(10_7, 4_0) __TVOS_PROHIBITED;

对焦选项

typedef NS_ENUM(NSInteger, AVCaptureFocusMode) {
AVCaptureFocusModeLocked              = 0,
AVCaptureFocusModeAutoFocus           = 1,
AVCaptureFocusModeContinuousAutoFocus = 2,
} NS_AVAILABLE(10_7, 4_0) __TVOS_PROHIBITED;

曝光选项

typedef NS_ENUM(NSInteger, AVCaptureExposureMode) {
AVCaptureExposureModeLocked                            = 0,
AVCaptureExposureModeAutoExpose                        = 1,
AVCaptureExposureModeContinuousAutoExposure            = 2,
AVCaptureExposureModeCustom NS_ENUM_AVAILABLE_IOS(8_0) = 3,
} NS_AVAILABLE(10_7, 4_0) __TVOS_PROHIBITED;

白平衡选项

typedef NS_ENUM(NSInteger, AVCaptureWhiteBalanceMode) {
AVCaptureWhiteBalanceModeLocked                      = 0,
AVCaptureWhiteBalanceModeAutoWhiteBalance            = 1,
AVCaptureWhiteBalanceModeContinuousAutoWhiteBalance  = 2,
} NS_AVAILABLE(10_7, 4_0) __TVOS_PROHIBITED;

7.距离调整

typedef NS_ENUM(NSInteger, AVCaptureAutoFocusRangeRestriction) {
AVCaptureAutoFocusRangeRestrictionNone = 0,
AVCaptureAutoFocusRangeRestrictionNear = 1,
AVCaptureAutoFocusRangeRestrictionFar = 2,

} NS_AVAILABLE_IOS(7_0);

1.2 获取硬件的输入流

-(AVCaptureDeviceInput *)input{
 if (_input == nil) {
     _input = [[AVCaptureDeviceInput alloc] initWithDevice:self.device error:nil];
 }
 return _input;
}

创建输入流的时候，会弹出alert向用户获取相机权限
1.3 需要一个用来协调输入和输出数据的会话，然后把input添加到会话中

-(AVCaptureSession *)session{
 if (_session == nil) {
     _session = [[AVCaptureSession alloc] init];
     if ([_session canAddInput:self.input]) {
         [_session addInput:self.input];
     }
 }
 return _session;
}

1.4 然后我们需要一个预览图像的层

-(AVCaptureVideoPreviewLayer *)previewLayer{
 if (_previewLayer == nil) {
     _previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.session];
     _previewLayer.frame = self.view.layer.bounds;
 }
 return _previewLayer;
}

1.5 最后把previewLayer添加到self.view.layer上

[self.view.layer addSublayer:self.previewLayer];

1.6 找个合适的位置，让session运行起来，比如viewWillAppear

-(void)viewWillAppear:(BOOL)animated{
 [super viewWillAppear:animated];
 [self.session startRunning];
}

搞一个按钮用来控制手电筒

#pragma mark - 手电筒
-(void)openTorch:(UIButton*)button{
 button.selected = !button.selected;
 Class captureDeviceClass = NSClassFromString(@"AVCaptureDevice");
 if (captureDeviceClass != nil) {
     if ([self.device hasTorch] && [self.device hasFlash]){
         [self.device lockForConfiguration:nil];
         if (button.selected) {
             [self.device setTorchMode:AVCaptureTorchModeOn];
         } else {
             [self.device setTorchMode:AVCaptureTorchModeOff];
         }
         [self.device unlockForConfiguration];
     }
 }
}

再搞一个按钮来切换前后置摄像头

pragma mark - 切换前后摄像头

-(void)switchCamera{
 NSUInteger cameraCount = [[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo] count];
 if (cameraCount > 1) {
     AVCaptureDevice *newCamera = nil;
     AVCaptureDeviceInput *newInput = nil;
     AVCaptureDevicePosition position = [[self.input device] position];
     if (position == AVCaptureDevicePositionFront){
         newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack];
     }else {
         newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront];
     }
     newInput = [AVCaptureDeviceInput deviceInputWithDevice:newCamera error: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];
     }
 }
}

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

使用AVCaptureStillImageOutput捕获静态图片

4.1 创建一个AVCaptureStillImageOutput对象

-(AVCaptureStillImageOutput *)stillImageOutput{
 if (_stillImageOutput == nil) {
     _stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
 }
 return _stillImageOutput;
}

4.2 将stillImageOutput添加到session中

if ([_session canAddOutput:self.stillImageOutput]) {
    [_session addOutput:self.stillImageOutput];
}

4.3 搞个拍照按钮，截取静态图片

//AVCaptureStillImageOutput截取静态图片，会有快门声

-(void)screenshot{
 AVCaptureConnection * videoConnection = [self.stillImageOutput connectionWithMediaType:AVMediaTypeVideo];
 if (!videoConnection) {
     NSLog(@"take photo failed!");
     return;
 }

 [self.stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
     if (imageDataSampleBuffer == NULL) {
         return;
     }
     NSData * imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
     UIImage *image = [UIImage imageWithData:imageData];
     [self saveImageToPhotoAlbum:image];
 }];
}

使用AVCaptureVideoOutput实时获取预览图像

5.1 创建AVCaptureVideoOutput对象

-(AVCaptureVideoDataOutput *)videoDataOutput{
 if (_videoDataOutput == nil) {
     _videoDataOutput = [[AVCaptureVideoDataOutput alloc] init];
     [_videoDataOutput setSampleBufferDelegate:self queue:dispatch_get_main_queue()];
     [_videoDataOutput setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey]];//设置像素格式
 }
 return _videoDataOutput;
}

5.2 将videoDataOutput添加session中

if ([_session canAddOutput:self.videoDataOutput]) {
    [_session addOutput:self.videoDataOutput];
}

5.3 遵守AVCaptureVideoDataOutputSampleBufferDelegate协议，并实现它的代理方法

pragma mark - AVCaptureVideoDataOutputSampleBufferDelegate

#pragma mark - AVCaptureVideoDataOutputSampleBufferDelegate
//AVCaptureVideoDataOutput获取实时图像

-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection{
 [connection setVideoOrientation:AVCaptureVideoOrientationPortrait];
 largeImage = [self imageFromSampleBuffer:sampleBuffer];
}

5.4 实现imageFromSampleBuffer:方法，将CMSampleBufferRef转为NSImage

//CMSampleBufferRef转NSImage
-(UIImage *)imageFromSampleBuffer:(CMSampleBufferRef)sampleBuffer{
 // 为媒体数据设置一个CMSampleBuffer的Core Video图像缓存对象
 CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
 // 锁定pixel buffer的基地址
 CVPixelBufferLockBaseAddress(imageBuffer, 0);
 // 得到pixel buffer的基地址
 void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);
 // 得到pixel buffer的行字节数
 size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
 // 得到pixel buffer的宽和高
 size_t width = CVPixelBufferGetWidth(imageBuffer);
 size_t height = CVPixelBufferGetHeight(imageBuffer);
 // 创建一个依赖于设备的RGB颜色空间
 CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
 // 用抽样缓存的数据创建一个位图格式的图形上下文（graphics context）对象
 CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
 // 根据这个位图context中的像素数据创建一个Quartz image对象
 CGImageRef quartzImage = CGBitmapContextCreateImage(context);
 // 解锁pixel buffer
 CVPixelBufferUnlockBaseAddress(imageBuffer,0);
 // 释放context和颜色空间
 CGContextRelease(context); CGColorSpaceRelease(colorSpace);
 // 用Quartz image创建一个UIImage对象image
 UIImage *image = [UIImage imageWithCGImage:quartzImage];
 // 释放Quartz image对象
 CGImageRelease(quartzImage);
 return (image);
}

5.5截取静态图

[_session setSessionPreset:AVCaptureSessionPreset1920x1080];

smallImage = [largeImage imageCompressTargetSize:CGSizeMake(512.0f, 512.0f)];

使用AVCaptureMetadataOutput识别二维码

6.1 创建AVCaptureMetadataOutput对象

-(AVCaptureMetadataOutput *)metadataOutput{
 if (_metadataOutput == nil) {
     _metadataOutput = [[AVCaptureMetadataOutput alloc]init];
     [_metadataOutput setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
     //设置扫描区域
     _metadataOutput.rectOfInterest = self.view.bounds;
 }
 return _metadataOutput;
}

6.2 将metadataOutput添加到session中，并且设置扫描类型

if ([_session canAddOutput:self.metadataOutput]) {
    [_session addOutput:self.metadataOutput];
    //设置扫码格式
    self.metadataOutput.metadataObjectTypes = @[
                                                AVMetadataObjectTypeQRCode,
                                                AVMetadataObjectTypeEAN13Code,
                                                AVMetadataObjectTypeEAN8Code,
                                                AVMetadataObjectTypeCode128Code
                                                ];
}

6.3 遵守AVCaptureMetadataOutputObjectsDelegate协议，并实现其代理方法

#pragma mark - AVCaptureMetadataOutputObjectsDelegate
-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection{
 if (metadataObjects.count>0) {
     [self.session stopRunning];
     AVMetadataMachineReadableCodeObject *metadataObject = [metadataObjects objectAtIndex :0];
     NSLog(@"二维码内容 ： %@",metadataObject.stringValue);
 }
}

关于人脸识别

人脸识别也是基于AVCaptureMetadataOutput实现的，跟二维码识别的区别在于，扫描类型：

self.metadataOutput.metadataObjectTypes = @[AVMetadataObjectTypeFace];

#pragma mark - AVCaptureMetadataOutputObjectsDelegate
-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection{
 if (metadataObjects.count>0) {
     [self.session stopRunning];
     AVMetadataMachineReadableCodeObject *metadataObject = [metadataObjects objectAtIndex :0];
     if (metadataObject.type == AVMetadataObjectTypeFace) {
         AVMetadataObject *objec = [self.previewLayer transformedMetadataObjectForMetadataObject:metadataObject];
         NSLog(@"%@",objec);
     }
 }
}

内容根据网文整理，仅供个人学习使用，如有侵权，请联系作者删除。