iOS人脸识别、自定义相机、图像扫描、系统自带二维码识别

前段时间遇到一个需求,需要实时扫描图像,并且设定摄像头的尺寸为1080x1920,然后从中间截取出512x512的图片传给第三方SDK做进一步业务处理,直到SDK返回正确的处理结果。

一顿Google,发现图像预览、人脸识别、二维码识别这些苹果都帮我们做好了,而且它们都是基于AVFoundation框架实现的。

话不多说,上代码~!

用到的类,主要有这些:

//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
  1. 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];
         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有很多属性可以调整(注意调整device属性的时候需要上锁, 调整完再解锁):
    闪光灯

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

    前后置摄像头

    typedef NS_ENUM(NSInteger, AVCaptureDevicePosition) {
    AVCaptureDevicePositionUnspecified         = 0,
    AVCaptureDevicePositionBack                = 1,
    AVCaptureDevicePositionFront               = 2
    } NS_AVAILABLE(10_7, 4_0) __TVOS_PROHIBITED;

    手电筒

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

    对焦

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

    曝光

    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

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

    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];
    }
  2. 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];
         }
     }
    }
  3. 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;
    }
  4. 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];
     }];
    }
  5. 使用AVCaptureVideoOutput实时获取预览图像,这也是楼主的项目需求所在

    5.1 创建AVCaptureVideoOutput对象

    -(AVCaptureVideoDataOutput *)videoDataOutput{
     if (_videoDataOutput == nil) {
         _videoDataOutput = [[AVCaptureVideoDataOutput alloc] init];
         [_videoDataOutput setSampleBufferDelegate:self queue:dispatch_get_main_queue()];
     }
     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
    //AVCaptureVideoDataOutput获取实时图像,这个代理方法的回调频率很快,几乎与手机屏幕的刷新频率一样快
    -(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection{
         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);
    }

    眼看大功告成,结果一运行,创建core graphic上下文的时候报错:

    CGBitmapContextCreate: invalid data bytes/row: should be at least 7680 for 8 integer bits/component, 3 components, kCGImageAlphaPremultipliedFirst.**
    CGBitmapContextCreateImage: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.**

    又是一通Google,发现stackoverflow上很多这种问答,楼主英语不好,又是一通翻译,发现大家都是在说像素组件位数什么的,摸索半天找到解决办法,设置videoDataOutput的像素格式:

    [_videoDataOutput setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey]];

    再运行,还有问题,获取到的图片是颠倒的,尼玛,真是多灾多难,不过这个简单,很快找到解决方法,设置一下视频的方向:

    #pragma mark - AVCaptureVideoDataOutputSampleBufferDelegate
    //AVCaptureVideoDataOutput获取实时图像,这个代理方法的回调频率很快,几乎与手机屏幕的刷新频率一样快
    -(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection{
     [connection setVideoOrientation:AVCaptureVideoOrientationPortrait];
     largeImage = [self imageFromSampleBuffer:sampleBuffer];
    }

    5.5 还记得楼主一开始的需求吗,设定摄像头的尺寸为1080x1920,然后从中间截取出512x512的图片传给第三方SDK做进一步业务处理:

    [_session setSessionPreset:AVCaptureSessionPreset1920x1080];
    smallImage = [largeImage imageCompressTargetSize:CGSizeMake(512.0f, 512.0f)];

    到这里为止,楼主的需求就大功告成啦

  6. 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);
     }
    }
  7. 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);
         }
     }
    }

    至于怎么利用它来实现具体的功能需求,楼主也很方哈,这里有个链接可以参考一下:基于 OpenCV 的人脸识别


好啦,就这么多了,代码在这里,水平有限,有不对的地方还请多多指教
参考资料:iOS 上的相机捕捉



文/戴尼玛(简书作者)
原文链接:http://www.jianshu.com/p/61ca3a917fe5
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”。

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