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iOS 相机流人脸识别(一)-人脸框检测(基于iOS原生)

2018-07-31  本文已影响469人  会飞的大马猴
  • 近几年随着移动设备硬件设备越来越优各种美颜相机App应运而生,美颜、瘦脸、添加挂件等等一系列的功能,这其中的原理一定离不开一个关键的技术,那就是人脸识别

一般的检测流程

(1) 人脸检测
检测图片中是否有人脸,或者有多少个人脸,同时会给出人脸的位置信息
(2) 人脸关键点检测
第一步我们找出来图中是否有人脸的信息,然后通过人脸的位置,与图片信息,获取人脸的关键点
(3) 处理信息
通过关键点,来做一些你需要的东西

扫盲:什么是关键点

我们来看一张图


image.png

这张图通过 68 个点描述了人脸的轮廓,这 68 个点 就是关键点,也有 5 个点的关键点和其他的规格;

人脸检测

今天我们来通过iOS系统本身的AVFoundation 框架 来检测视频流中出现的人脸,并把检测出来的框绘制到视频流中,我们先看一下效果是什么样子的


IMB_hHOF7t.GIF

Mars 可能太酷 都检测不到!

  • 原料

  • AVFoundation
  • opencv2.framework 下载opencv2
    ps:opencv 有的库带有iOS 用的一些方法 有的版本不带,我忘记了 大家自行下载查阅,没有的话也可以自己写方法,主要是做转换用的,你的controller的.m文件要换成.mm
#import "ViewController.h"
#import <AVFoundation/AVFoundation.h>
#import <opencv2/imgproc/types_c.h>
#import <opencv2/imgproc/imgproc_c.h>
#import <opencv2/imgcodecs/ios.h>
#import <opencv2/opencv.hpp>
@interface ViewController ()<AVCaptureVideoDataOutputSampleBufferDelegate, AVCaptureMetadataOutputObjectsDelegate>
@property (nonatomic,strong) AVCaptureSession *session;
@property (nonatomic,strong) UIImageView *cameraView;
@property (nonatomic,strong) dispatch_queue_t sample;
@property (nonatomic,strong) dispatch_queue_t faceQueue;

@property (nonatomic,copy) NSArray *currentMetadata; //?< 如果检测到了人脸系统会返回一个数组 我们将这个数组存起来

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    _currentMetadata = [NSMutableArray arrayWithCapacity:0];
   
    [self.view addSubview: self.cameraView];
    
    _sample = dispatch_queue_create("sample", NULL);
    _faceQueue = dispatch_queue_create("face", NULL);
    
    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    AVCaptureDevice *deviceF;
    for (AVCaptureDevice *device in devices )
    {
        if ( device.position == AVCaptureDevicePositionFront )
        {
            deviceF = device;
            break;
        }
    }
    
    AVCaptureDeviceInput*input = [[AVCaptureDeviceInput alloc] initWithDevice:deviceF error:nil];
    AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init];
    
    [output setSampleBufferDelegate:self queue:_sample];
    
    AVCaptureMetadataOutput *metaout = [[AVCaptureMetadataOutput alloc] init];
    [metaout setMetadataObjectsDelegate:self queue:_faceQueue];
    self.session = [[AVCaptureSession alloc] init];
    
    
    [self.session beginConfiguration];
    if ([self.session canAddInput:input]) {
        [self.session addInput:input];
    }
    
    if ([self.session canSetSessionPreset:AVCaptureSessionPreset640x480]) {
        [self.session setSessionPreset:AVCaptureSessionPreset640x480];
    }
    if ([self.session canAddOutput:output]) {
        [self.session addOutput:output];
    }
    
    if ([self.session canAddOutput:metaout]) {
        [self.session addOutput:metaout];
    }
    [self.session commitConfiguration];
    
    
    NSString     *key           = (NSString *)kCVPixelBufferPixelFormatTypeKey;
    NSNumber     *value         = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA];
    NSDictionary *videoSettings = [NSDictionary dictionaryWithObject:value forKey:key];
    
    [output setVideoSettings:videoSettings];
    
    //这里 我们告诉要检测到人脸 就给我一些反应,里面还有QRCode 等 都可以放进去,就是 如果视频流检测到了你要的 就会出发下面第二个代理方法
    [metaout setMetadataObjectTypes:@[AVMetadataObjectTypeFace]];
    
    AVCaptureSession* session = (AVCaptureSession *)self.session;
    //前置摄像头一定要设置一下 要不然画面是镜像
    for (AVCaptureVideoDataOutput* output in session.outputs) {
        for (AVCaptureConnection * av in output.connections) {
            //判断是否是前置摄像头状态
            if (av.supportsVideoMirroring) {
                //镜像设置
                av.videoOrientation = AVCaptureVideoOrientationPortrait;
                av.videoMirrored = YES;
            }
        }
    }
    [self.session startRunning];

}
#pragma mark - AVCaptureSession Delegate -

- (void)captureOutput:(AVCaptureOutput *)output didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
    
    NSMutableArray *bounds = [NSMutableArray arrayWithCapacity:0];
    //每一帧,我们都看一下  self.currentMetadata 里面有没有东西,然后将里面的 
   //AVMetadataFaceObject 转换成  AVMetadataObject,其中AVMetadataObject 的bouns 就是人脸的位置 ,我们将bouns 存到数组中
    for (AVMetadataFaceObject *faceobject in self.currentMetadata) {
        AVMetadataObject *face = [output transformedMetadataObjectForMetadataObject:faceobject connection:connection];
        [bounds addObject:[NSValue valueWithCGRect:face.bounds]];
    }
}

- (void)captureOutput:(AVCaptureOutput *)output didOutputMetadataObjects:(NSArray<__kindof AVMetadataObject *> *)metadataObjects fromConnection:(AVCaptureConnection *)connection
{
    //当检测到了人脸会走这个回调
    _currentMetadata = metadataObjects;
}



- (UIImage*)imageFromPixelBuffer:(CMSampleBufferRef)p {
    CVImageBufferRef buffer;
    buffer = CMSampleBufferGetImageBuffer(p);
    
    CVPixelBufferLockBaseAddress(buffer, 0);
    uint8_t *base;
    size_t width, height, bytesPerRow;
    base = (uint8_t *)CVPixelBufferGetBaseAddress(buffer);
    width = CVPixelBufferGetWidth(buffer);
    height = CVPixelBufferGetHeight(buffer);
    bytesPerRow = CVPixelBufferGetBytesPerRow(buffer);
    
    CGColorSpaceRef colorSpace;
    CGContextRef cgContext;
    colorSpace = CGColorSpaceCreateDeviceRGB();
    cgContext = CGBitmapContextCreate(base, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
    CGColorSpaceRelease(colorSpace);
    
    CGImageRef cgImage;
    UIImage *image;
    cgImage = CGBitmapContextCreateImage(cgContext);
    image = [UIImage imageWithCGImage:cgImage];
    CGImageRelease(cgImage);
    CGContextRelease(cgContext);
    
    CVPixelBufferUnlockBaseAddress(buffer, 0);
    
    
    return image;
}

- (UIImageView *)cameraView
{
    if (!_cameraView) {
        _cameraView = [[UIImageView alloc] initWithFrame:self.view.bounds];
        //不拉伸
        _cameraView.contentMode = UIViewContentModeScaleAspectFill;
    }
    return _cameraView;
}

注意的地方

  • 1.output的设置一定在添加之后
  • 2.info.plist 要设置相机权限 Privacy - Camera Usage Description

现在我们视频流拿到了 但是还没有显示出来,下面我们会通过opencv 将人脸框绘制在视频流上,并通过UIImageView 将 处理后的图像显示出来

将人脸框绘制到显示的视频流上

(1). 转换

我们先写一个方法 将CMSampleBufferRef 转换成 UIImage(其实也可以直接CMSampleBufferRef 转换成cv::Mat)

- (UIImage*)imageFromPixelBuffer:(CMSampleBufferRef)p {
    CVImageBufferRef buffer;
    buffer = CMSampleBufferGetImageBuffer(p);
    
    CVPixelBufferLockBaseAddress(buffer, 0);
    uint8_t *base;
    size_t width, height, bytesPerRow;
    base = (uint8_t *)CVPixelBufferGetBaseAddress(buffer);
    width = CVPixelBufferGetWidth(buffer);
    height = CVPixelBufferGetHeight(buffer);
    bytesPerRow = CVPixelBufferGetBytesPerRow(buffer);
    
    CGColorSpaceRef colorSpace;
    CGContextRef cgContext;
    colorSpace = CGColorSpaceCreateDeviceRGB();
    cgContext = CGBitmapContextCreate(base, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
    CGColorSpaceRelease(colorSpace);
    
    CGImageRef cgImage;
    UIImage *image;
    cgImage = CGBitmapContextCreateImage(cgContext);
    image = [UIImage imageWithCGImage:cgImage];
    CGImageRelease(cgImage);
    CGContextRelease(cgContext);
    
    CVPixelBufferUnlockBaseAddress(buffer, 0);
    
    
    return image;
}

(2).绘制

我们在继续在 AVCaptureVideoDataOutputSampleBufferDelegate 去处理视频流,已经可以拿到 有关人脸的信息了 我们直接绘制上去就可以了

- (void)captureOutput:(AVCaptureOutput *)output didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
    
    NSMutableArray *bounds = [NSMutableArray arrayWithCapacity:0];
    for (AVMetadataFaceObject *faceobject in self.currentMetadata) {
        AVMetadataObject *face = [output transformedMetadataObjectForMetadataObject:faceobject connection:connection];
        [bounds addObject:[NSValue valueWithCGRect:face.bounds]];
    }
   
   //转换成UIImage
    UIImage *image = [self imageFromPixelBuffer:sampleBuffer];
    cv::Mat mat;
    //转换成cv::Mat
    UIImageToMat(image, mat);
    
    for (NSValue *rect in bounds) {
        CGRect r = [rect CGRectValue];
        //画框
        cv::rectangle(mat, cv::Rect(r.origin.x,r.origin.y,r.size.width,r.size.height), cv::Scalar(255,0,0,1));

    }
    
    //这里不考虑性能 直接怼Image
    dispatch_async(dispatch_get_main_queue(), ^{
       self.cameraView.image = MatToUIImage(mat);
    });
}

忘记一个东西 依赖库 大家别忘记 点一波

image.png
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